News About GNU Fortran
**********************

Changes made to recent versions of GNU Fortran are listed below, with the most recent version first.

The changes are generally listed in order:

 1. Code-generation and run-time-library bug-fixes

 2. Compiler and run-time-library crashes involving valid code that have been fixed

 3. New features

 4. Fixes and enhancements to existing features

 5. New diagnostics

 6. Internal improvements

 7. Miscellany

This order is not strict---for example, some items involve a combination of these elements.

Note that two variants of g77 are tracked below. The egcs variant is described vis-a-vis previous versions of egcs and/or an official FSF version, as appropriate.

Therefore, egcs versions sometimes have multiple listings to help clarify how they differ from other versions, though this can make getting a complete picture of what a particular egcs version contains somewhat more difficult.

An online, ``live'' version of this document (derived directly from the up-to-date mainline version of g77 within egcs) is available at http://egcs.cygnus.com/onlinedocs/g77_news.html.

In 0.5.24 and egcs 1.1.2 (versus 0.5.23 and 1.1.1):
===================================================

  * Fix the IDate Intrinsic (VXT) so the returned year is in the documented, non-Y2K-compliant range of 0--99, instead of being returned as 100 in the year 2000.

  * Fix the Date_and_Time intrinsic (in libg2c) to return the milliseconds value properly in VALUES(8).

  * Fix the LStat intrinsic (in libg2c) to return device-ID information properly in SARRAY(7).

  * Improve documentation.

In 0.5.24 and egcs 1.1.1 (versus 0.5.23 and 1.1):
=================================================

  * Fix libg2c so it performs an implicit ENDFILE operation (as appropriate) whenever a REWIND is done.

     (This bug was introduced in 0.5.23 and egcs 1.1 in g77's version of libf2c.)

  * Fix libg2c so it no longer crashes with a spurious diagnostic upon doing any I/O following a direct formatted write.

     (This bug was introduced in 0.5.23 and egcs 1.1 in g77's version of libf2c.)

  * Fix g77 so it no longer crashes compiling references to the Rand intrinsic on some systems.

  * Fix g77 portion of installation process so it works better on some systems (those with shells requiring else true clauses on if constructs for the completion code to be set properly).

In egcs 1.1 (versus 0.5.24):
============================

  * Fix g77 crash compiling code containing the construct CMPLX(0.) or similar.

  * Fix g77 crash (or apparently infinite run-time) when compiling certain complicated expressions involving COMPLEX arithmetic (especially multiplication).

  * Fix a code-generation bug that afflicted Intel x86 targets when -O2 was specified compiling, for example, an old version of the DNRM2 routine.

     The x87 coprocessor stack was being mismanaged in cases involving assigned GOTO and ASSIGN.

  * Align static double-precision variables and arrays on Intel x86 targets regardless of whether -malign-double is specified.

     Generally, this affects only local variables and arrays having the SAVE attribute or given initial values via DATA.

In egcs 1.1 (versus egcs 1.0.3):
================================

  * Fix bugs in the libU77 intrinsic HostNm that wrote one byte beyond the end of its CHARACTER argument, and in the libU77 intrinsics GMTime and LTime that overwrote their arguments.

  * Assumed arrays with negative bounds (such as REAL A(-1:*)) no longer elicit spurious diagnostics from g77, even on systems with pointers having different sizes than integers.

     This bug is not known to have existed in any recent version of gcc. It was introduced in an early release of egcs.

  * Valid combinations of EXTERNAL, passing that external as a dummy argument without explicitly giving it a type, and, in a subsequent program unit, referencing that external as an external function with a different type no longer crash g77.

  * CASE DEFAULT no longer crashes g77.

  * The -Wunused option no longer issues a spurious warning about the ``master'' procedure generated by g77 for procedures containing ENTRY statements.

  * Support FORMAT(I<EXPR>) when EXPR is a compile-time constant INTEGER expression.

  * Fix g77 -g option so procedures that use ENTRY can be stepped through, line by line, in gdb.

  * Allow any REAL argument to intrinsics Second and CPU_Time.

  * Use tempnam, if available, to open scratch files (as in OPEN(STATUS='SCRATCH')) so that the TMPDIR environment variable, if present, is used.

  * g77's version of libf2c separates out the setting of global state (such as command-line arguments and signal handling) from main.o into distinct, new library archive members.

     This should make it easier to write portable applications that have their own (non-Fortran) main() routine properly set up the libf2c environment, even when libf2c (now libg2c) is a shared library.

  * g77 no longer installs the f77 command and f77.1 man page in the /usr or /usr/local heirarchy, even if the f77-install-ok file exists in the source or build directory. See the installation documentation for more information.

  * g77 no longer installs the libf2c.a library and f2c.h include file in the /usr or /usr/local heirarchy, even if the f2c-install-ok or f2c-exists-ok files exist in the source or build directory. See the installation documentation for more information.

  * The libf2c.a library produced by g77 has been renamed to libg2c.a. It is installed only in the gcc ``private'' directory heirarchy, gcc-lib. This allows system administrators and users to choose which version of the libf2c library from netlib they wish to use on a case-by-case basis. See the installation documentation for more information.

  * The f2c.h include (header) file produced by g77 has been renamed to g2c.h. It is installed only in the gcc ``private'' directory heirarchy, gcc-lib. This allows system administrators and users to choose which version of the include file from netlib they wish to use on a case-by-case basis. See the installation documentation for more information.

  * The g77 command now expects the run-time library to be named libg2c.a instead of libf2c.a, to ensure that a version other than the one built and installed as part of the same g77 version is picked up.

  * During the configuration and build process, g77 creates subdirectories it needs only as it needs them. Other cleaning up of the configuration and build process has been performed as well.

  * install-info now used to update the directory of Info documentation to contain an entry for g77 (during installation).

  * Some diagnostics have been changed from warnings to errors, to prevent inadvertent use of the resulting, probably buggy, programs. These mostly include diagnostics about use of unsupported features in the OPEN, INQUIRE, READ, and WRITE statements, and about truncations of various sorts of constants.

  * Improve compilation of FORMAT expressions so that a null byte is appended to the last operand if it is a constant. This provides a cleaner run-time diagnostic as provided by libf2c for statements like PRINT '(I1', 42.

  * Improve documentation and indexing.

  * The upgrade to libf2c as of 1998-06-18 should fix a variety of problems, including those involving some uses of the T format specifier, and perhaps some build (porting) problems as well.

In 0.5.24 and egcs 1.1 (versus 0.5.23):
=======================================

  * g77 no longer produces incorrect code and initial values for EQUIVALENCE and COMMON aggregates that, due to ``unnatural'' ordering of members vis-a-vis their types, require initial padding.

  * g77 no longer crashes when compiling code containing specification statements such as INTEGER(KIND=7) PTR.

  * g77 no longer crashes when compiling code such as J = SIGNAL(1, 2).

  * g77 now treats %LOC(EXPR) and LOC(EXPR) as ``ordinary'' expressions when they are used as arguments in procedure calls. This change applies only to global (filewide) analysis, making it consistent with how g77 actually generates code for these cases.

     Previously, g77 treated these expressions as denoting special ``pointer'' arguments for the purposes of filewide analysis.

  * The g77 driver now ensures that -lg2c is specified in the link phase prior to any occurrence of -lm. This prevents accidentally linking to a routine in the SunOS4 -lm library when the generated code wants to link to the one in libf2c (libg2c).

  * g77 emits more debugging information when -g is used.

     This new information allows, for example, which __g77_length_a to be used in gdb to determine the type of the phantom length argument supplied with CHARACTER variables.

     This information pertains to internally-generated type, variable, and other information, not to the longstanding deficiencies vis-a-vis COMMON and EQUIVALENCE.

  * The F90 Date_and_Time intrinsic now is supported.

  * The F90 System_Clock intrinsic allows the optional arguments (except for the Count argument) to be omitted.

  * Upgrade to libf2c as of 1998-06-18.

  * Improve documentation and indexing.

In 0.5.23 (versus 0.5.22):
==========================

  * This release contains several regressions against version 0.5.22 of g77, due to using the ``vanilla'' gcc back end instead of patching it to fix a few bugs and improve performance in a few cases.

     Features that have been dropped from this version of g77 due to their being implemented via g77-specific patches to the gcc back end in previous releases include:

       -- Support for __restrict__ keyword, the options -fargument-alias, -fargument-noalias, and -fargument-noalias-global, and the corresponding alias-analysis code.

          (egcs has the alias-analysis code, but not the __restrict__ keyword. egcs g77 users benefit from the alias-analysis code despite the lack of the __restrict__ keyword, which is a C-language construct.)

       -- Support for the GNU compiler options -fmove-all-movables, -freduce-all-givs, and -frerun-loop-opt.

          (egcs supports these options. g77 users of egcs benefit from them even if they are not explicitly specified, because the defaults are optimized for g77 users.)

       -- Support for the -W option warning about integer division by zero.

       -- The Intel x86-specific option -malign-double applying to stack-allocated data as well as statically-allocate data.

     Note that the gcc/f/gbe/ subdirectory has been removed from this distribution as a result of g77 no longer including patches for the gcc back end.

  * Fix bugs in the libU77 intrinsic HostNm that wrote one byte beyond the end of its CHARACTER argument, and in the libU77 intrinsics GMTime and LTime that overwrote their arguments.

  * Support gcc version 2.8, and remove support for prior versions of gcc.

  * Remove support for the --driver option, as g77 now does all the driving, just like gcc.

  * CASE DEFAULT no longer crashes g77.

  * Valid combinations of EXTERNAL, passing that external as a dummy argument without explicitly giving it a type, and, in a subsequent program unit, referencing that external as an external function with a different type no longer crash g77.

  * g77 no longer installs the f77 command and f77.1 man page in the /usr or /usr/local heirarchy, even if the f77-install-ok file exists in the source or build directory. See the installation documentation for more information.

  * g77 no longer installs the libf2c.a library and f2c.h include file in the /usr or /usr/local heirarchy, even if the f2c-install-ok or f2c-exists-ok files exist in the source or build directory. See the installation documentation for more information.

  * The libf2c.a library produced by g77 has been renamed to libg2c.a. It is installed only in the gcc ``private'' directory heirarchy, gcc-lib. This allows system administrators and users to choose which version of the libf2c library from netlib they wish to use on a case-by-case basis. See the installation documentation for more information.

  * The f2c.h include (header) file produced by g77 has been renamed to g2c.h. It is installed only in the gcc ``private'' directory heirarchy, gcc-lib. This allows system administrators and users to choose which version of the include file from netlib they wish to use on a case-by-case basis. See the installation documentation for more information.

  * The g77 command now expects the run-time library to be named libg2c.a instead of libf2c.a, to ensure that a version other than the one built and installed as part of the same g77 version is picked up.

  * The -Wunused option no longer issues a spurious warning about the ``master'' procedure generated by g77 for procedures containing ENTRY statements.

  * g77's version of libf2c separates out the setting of global state (such as command-line arguments and signal handling) from main.o into distinct, new library archive members.

     This should make it easier to write portable applications that have their own (non-Fortran) main() routine properly set up the libf2c environment, even when libf2c (now libg2c) is a shared library.

  * During the configuration and build process, g77 creates subdirectories it needs only as it needs them, thus avoiding unnecessary creation of, for example, stage1/f/runtime when doing a non-bootstrap build. Other cleaning up of the configuration and build process has been performed as well.

  * install-info now used to update the directory of Info documentation to contain an entry for g77 (during installation).

  * Some diagnostics have been changed from warnings to errors, to prevent inadvertent use of the resulting, probably buggy, programs. These mostly include diagnostics about use of unsupported features in the OPEN, INQUIRE, READ, and WRITE statements, and about truncations of various sorts of constants.

  * Improve documentation and indexing.

  * Upgrade to libf2c as of 1998-04-20.

     This should fix a variety of problems, including those involving some uses of the T format specifier, and perhaps some build (porting) problems as well.

In 0.5.22 (versus 0.5.21):
==========================

  * Fix code generation for iterative DO loops that have one or more references to the iteration variable, or to aliases of it, in their control expressions. For example, DO 10 J=2,J now is compiled correctly.

  * Fix a code-generation bug that afflicted Intel x86 targets when -O2 was specified compiling, for example, an old version of the DNRM2 routine.

     The x87 coprocessor stack was being mismanaged in cases involving assigned GOTO and ASSIGN.

  * Fix DTime intrinsic so as not to truncate results to integer values (on some systems).

  * Fix Signal intrinsic so it offers portable support for 64-bit systems (such as Digital Alphas running GNU/Linux).

  * Fix run-time crash involving NAMELIST on 64-bit machines such as Alphas.

  * Fix g77 version of libf2c so it no longer produces a spurious I/O recursion diagnostic at run time when an I/O operation (such as READ *,I) is interrupted in a manner that causes the program to be terminated via the f_exit routine (such as via C-c).

  * Fix g77 crash triggered by CASE statement with an omitted lower or upper bound.

  * Fix g77 crash compiling references to CPU_Time intrinsic.

  * Fix g77 crash (or apparently infinite run-time) when compiling certain complicated expressions involving COMPLEX arithmetic (especially multiplication).

  * Fix g77 crash on statements such as PRINT *, (REAL(Z(I)),I=1,2), where Z is DOUBLE COMPLEX.

  * Fix a g++ crash.

  * Support FORMAT(I<EXPR>) when EXPR is a compile-time constant INTEGER expression.

  * Fix g77 -g option so procedures that use ENTRY can be stepped through, line by line, in gdb.

  * Fix a profiling-related bug in gcc back end for Intel x86 architecture.

  * Allow any REAL argument to intrinsics Second and CPU_Time.

  * Allow any numeric argument to intrinsics Int2 and Int8.

  * Use tempnam, if available, to open scratch files (as in OPEN(STATUS='SCRATCH')) so that the TMPDIR environment variable, if present, is used.

  * Rename the gcc keyword restrict to __restrict__, to avoid rejecting valid, existing, C programs. Support for restrict is now more like support for complex.

  * Fix -fpedantic to not reject procedure invocations such as I=J() and CALL FOO().

  * Fix -fugly-comma to affect invocations of only external procedures. Restore rejection of gratuitous trailing omitted arguments to intrinsics, as in I=MAX(3,4,,).

  * Fix compiler so it accepts -fgnu-intrinsics-* and -fbadu77-intrinsics-* options.

  * Improve diagnostic messages from libf2c so it is more likely that the printing of the active format string is limited to the string, with no trailing garbage being printed.

     (Unlike f2c, g77 did not append a null byte to its compiled form of every format string specified via a FORMAT statement. However, f2c would exhibit the problem anyway for a statement like PRINT '(I)garbage', 1 by printing (I)garbage as the format string.)

  * Improve compilation of FORMAT expressions so that a null byte is appended to the last operand if it is a constant. This provides a cleaner run-time diagnostic as provided by libf2c for statements like PRINT '(I1', 42.

  * Fix various crashes involving code with diagnosed errors.

  * Fix cross-compilation bug when configuring libf2c.

  * Improve diagnostics.

  * Improve documentation and indexing.

  * Upgrade to libf2c as of 1997-09-23. This fixes a formatted-I/O bug that afflicted 64-bit systems with 32-bit integers (such as Digital Alpha running GNU/Linux).

In egcs 1.0.2 (versus egcs 1.0.1):
==================================

  * Fix g77 crash triggered by CASE statement with an omitted lower or upper bound.

  * Fix g77 crash on statements such as PRINT *, (REAL(Z(I)),I=1,2), where Z is DOUBLE COMPLEX.

  * Fix -fPIC (such as compiling for ELF targets) on the Intel x86 architecture target so invalid assembler code is no longer produced.

  * Fix -fpedantic to not reject procedure invocations such as I=J() and CALL FOO().

  * Fix -fugly-comma to affect invocations of only external procedures. Restore rejection of gratuitous trailing omitted arguments to intrinsics, as in I=MAX(3,4,,).

  * Fix compiler so it accepts -fgnu-intrinsics-* and -fbadu77-intrinsics-* options.

In egcs 1.0.1 (versus egcs 1.0):
================================

  * Fix run-time crash involving NAMELIST on 64-bit machines such as Alphas.

In egcs 1.0 (versus 0.5.21):
============================

  * Version 1.0 of egcs contains several regressions against version 0.5.21 of g77, due to using the ``vanilla'' gcc back end instead of patching it to fix a few bugs and improve performance in a few cases.

     Features that have been dropped from this version of g77 due to their being implemented via g77-specific patches to the gcc back end in previous releases include:

       -- Support for the C-language restrict keyword.

       -- Support for the -W option warning about integer division by zero.

       -- The Intel x86-specific option -malign-double applying to stack-allocated data as well as statically-allocate data.

     Note that the gcc/f/gbe/ subdirectory has been removed from this distribution as a result of g77 being fully integrated with the egcs variant of the gcc back end.

  * Fix code generation for iterative DO loops that have one or more references to the iteration variable, or to aliases of it, in their control expressions. For example, DO 10 J=2,J now is compiled correctly.

  * Fix DTime intrinsic so as not to truncate results to integer values (on some systems).

  * Remove support for non-egcs versions of gcc.

  * Remove support for the --driver option, as g77 now does all the driving, just like gcc.

  * Allow any numeric argument to intrinsics Int2 and Int8.

  * Improve diagnostic messages from libf2c so it is more likely that the printing of the active format string is limited to the string, with no trailing garbage being printed.

     (Unlike f2c, g77 did not append a null byte to its compiled form of every format string specified via a FORMAT statement. However, f2c would exhibit the problem anyway for a statement like PRINT '(I)garbage', 1 by printing (I)garbage as the format string.)

  * Upgrade to libf2c as of 1997-09-23. This fixes a formatted-I/O bug that afflicted 64-bit systems with 32-bit integers (such as Digital Alpha running GNU/Linux).

In 0.5.21:
==========

  * Fix a code-generation bug introduced by 0.5.20 caused by loop unrolling (by specifying -funroll-loops or similar). This bug afflicted all code compiled by version 2.7.2.2.f.2 of gcc (C, C++, Fortran, and so on).

  * Fix a code-generation bug manifested when combining local EQUIVALENCE with a DATA statement that follows the first executable statement (or is treated as an executable-context statement as a result of using the -fpedantic option).

  * Fix a compiler crash that occured when an integer division by a constant zero is detected. Instead, when the -W option is specified, the gcc back end issues a warning about such a case. This bug afflicted all code compiled by version 2.7.2.2.f.2 of gcc (C, C++, Fortran, and so on).

  * Fix a compiler crash that occurred in some cases of procedure inlining. (Such cases became more frequent in 0.5.20.)

  * Fix a compiler crash resulting from using DATA or similar to initialize a COMPLEX variable or array to zero.

  * Fix compiler crashes involving use of AND, OR, or XOR intrinsics.

  * Fix compiler bug triggered when using a COMMON or EQUIVALENCE variable as the target of an ASSIGN or assigned-GOTO statement.

  * Fix compiler crashes due to using the name of a some non-standard intrinsics (such as FTELL or FPUTC) as such and as the name of a procedure or common block. Such dual use of a name in a program is allowed by the standard.

  * Place automatic arrays on the stack, even if SAVE or the -fno-automatic option is in effect. This avoids a compiler crash in some cases.

  * The -malign-double option now reliably aligns DOUBLE PRECISION optimally on Pentium and Pentium Pro architectures (586 and 686 in gcc).

  * New option -Wno-globals disables warnings about ``suspicious'' use of a name both as a global name and as the implicit name of an intrinsic, and warnings about disagreements over the number or natures of arguments passed to global procedures, or the natures of the procedures themselves.

     The default is to issue such warnings, which are new as of this version of g77.

  * New option -fno-globals disables diagnostics about potentially fatal disagreements analysis problems, such as disagreements over the number or natures of arguments passed to global procedures, or the natures of those procedures themselves.

     The default is to issue such diagnostics and flag the compilation as unsuccessful. With this option, the diagnostics are issued as warnings, or, if -Wno-globals is specified, are not issued at all.

     This option also disables inlining of global procedures, to avoid compiler crashes resulting from coding errors that these diagnostics normally would identify.

  * Diagnose cases where a reference to a procedure disagrees with the type of that procedure, or where disagreements about the number or nature of arguments exist. This avoids a compiler crash.

  * Fix parsing bug whereby g77 rejected a second initialization specification immediately following the first's closing / without an intervening comma in a DATA statement, and the second specification was an implied-DO list.

  * Improve performance of the gcc back end so certain complicated expressions involving COMPLEX arithmetic (especially multiplication) don't appear to take forever to compile.

  * Fix a couple of profiling-related bugs in gcc back end.

  * Integrate GNU Ada's (GNAT's) changes to the back end, which consist almost entirely of bug fixes. These fixes are circa version 3.10p of GNAT.

  * Include some other gcc fixes that seem useful in g77's version of gcc. (See gcc/ChangeLog for details---compare it to that file in the vanilla gcc-2.7.2.3.tar.gz distribution.)

  * Fix libU77 routines that accept file and other names to strip trailing blanks from them, for consistency with other implementations. Blanks may be forcibly appended to such names by appending a single null character (CHAR(0)) to the significant trailing blanks.

  * Fix CHMOD intrinsic to work with file names that have embedded blanks, commas, and so on.

  * Fix SIGNAL intrinsic so it accepts an optional third Status argument.

  * Fix IDATE() intrinsic subroutine (VXT form) so it accepts arguments in the correct order. Documentation fixed accordingly, and for GMTIME() and LTIME() as well.

  * Make many changes to libU77 intrinsics to support existing code more directly.

     Such changes include allowing both subroutine and function forms of many routines, changing MCLOCK() and TIME() to return INTEGER(KIND=1) values, introducing MCLOCK8() and TIME8() to return INTEGER(KIND=2) values, and placing functions that are intended to perform side effects in a new intrinsic group, badu77.

  * Improve libU77 so it is more portable.

  * Add options -fbadu77-intrinsics-delete, -fbadu77-intrinsics-hide, and so on.

  * Fix crashes involving diagnosed or invalid code.

  * g77 and gcc now do a somewhat better job detecting and diagnosing arrays that are too large to handle before these cause diagnostics during the assembler or linker phase, a compiler crash, or generation of incorrect code.

  * Make some fixes to alias analysis code.

  * Add support for restrict keyword in gcc front end.

  * Support gcc version 2.7.2.3 (modified by g77 into version 2.7.2.3.f.1), and remove support for prior versions of gcc.

  * Incorporate GNAT's patches to the gcc back end into g77's, so GNAT users do not need to apply GNAT's patches to build both GNAT and g77 from the same source tree.

  * Modify make rules and related code so that generation of Info documentation doesn't require compilation using gcc. Now, any ANSI C compiler should be adequate to produce the g77 documentation (in particular, the tables of intrinsics) from scratch.

  * Add INT2 and INT8 intrinsics.

  * Add CPU_TIME intrinsic.

  * Add ALARM intrinsic.

  * CTIME intrinsic now accepts any INTEGER argument, not just INTEGER(KIND=2).

  * Warn when explicit type declaration disagrees with the type of an intrinsic invocation.

  * Support *f771 entry in gcc specs file.

  * Fix typo in make rule g77-cross, used only for cross-compiling.

  * Fix libf2c build procedure to re-archive library if previous attempt to archive was interrupted.

  * Change gcc to unroll loops only during the last invocation (of as many as two invocations) of loop optimization.

  * Improve handling of -fno-f2c so that code that attempts to pass an intrinsic as an actual argument, such as CALL FOO(ABS), is rejected due to the fact that the run-time-library routine is, effectively, compiled with -ff2c in effect.

  * Fix g77 driver to recognize -fsyntax-only as an option that inhibits linking, just like -c or -S, and to recognize and properly handle the -nostdlib, -M, -MM, -nodefaultlibs, and -Xlinker options.

  * Upgrade to libf2c as of 1997-08-16.

  * Modify libf2c to consistently and clearly diagnose recursive I/O (at run time).

  * g77 driver now prints version information (such as produced by g77 -v) to stderr instead of stdout.

  * The .r suffix now designates a Ratfor source file, to be preprocessed via the ratfor command, available separately.

  * Fix some aspects of how gcc determines what kind of system is being configured and what kinds are supported. For example, GNU Linux/Alpha ELF systems now are directly supported.

  * Improve diagnostics.

  * Improve documentation and indexing.

  * Include all pertinent files for libf2c that come from netlib.bell-labs.com; give any such files that aren't quite accurate in g77's version of libf2c the suffix .netlib.

  * Reserve INTEGER(KIND=0) for future use.

In 0.5.20:
==========

  * The -fno-typeless-boz option is now the default.

     This option specifies that non-decimal-radix constants using the prefixed-radix form (such as Z'1234') are to be interpreted as INTEGER constants. Specify -ftypeless-boz to cause such constants to be interpreted as typeless.

     (Version 0.5.19 introduced -fno-typeless-boz and its inverse.)

  * Options -ff90-intrinsics-enable and -fvxt-intrinsics-enable now are the defaults.

     Some programs might use names that clash with intrinsic names defined (and now enabled) by these options or by the new libU77 intrinsics. Users of such programs might need to compile them differently (using, for example, -ff90-intrinsics-disable) or, better yet, insert appropriate EXTERNAL statements specifying that these names are not intended to be names of intrinsics.

  * The ALWAYS_FLUSH macro is no longer defined when building libf2c, which should result in improved I/O performance, especially over NFS.

     Note: If you have code that depends on the behavior of libf2c when built with ALWAYS_FLUSH defined, you will have to modify libf2c accordingly before building it from this and future versions of g77.

  * Dave Love's implementation of libU77 has been added to the version of libf2c distributed with and built as part of g77. g77 now knows about the routines in this library as intrinsics.

  * New option -fvxt specifies that the source file is written in VXT Fortran, instead of GNU Fortran.

  * The -fvxt-not-f90 option has been deleted, along with its inverse, -ff90-not-vxt.

     If you used one of these deleted options, you should re-read the pertinent documentation to determine which options, if any, are appropriate for compiling your code with this version of g77.

  * The -fugly option now issues a warning, as it likely will be removed in a future version.

     (Enabling all the -fugly-* options is unlikely to be feasible, or sensible, in the future, so users should learn to specify only those -fugly-* options they really need for a particular source file.)

  * The -fugly-assumed option, introduced in version 0.5.19, has been changed to better accommodate old and new code.

  * Make a number of fixes to the g77 front end and the gcc back end to better support Alpha (AXP) machines. This includes providing at least one bug-fix to the gcc back end for Alphas.

  * Related to supporting Alpha (AXP) machines, the LOC() intrinsic and %LOC() construct now return values of integer type that is the same width (holds the same number of bits) as the pointer type on the machine.

     On most machines, this won't make a difference, whereas on Alphas, the type these constructs return is INTEGER*8 instead of the more common INTEGER*4.

  * Emulate COMPLEX arithmetic in the g77 front end, to avoid bugs in complex support in the gcc back end. New option -fno-emulate-complex causes g77 to revert the 0.5.19 behavior.

  * Fix bug whereby REAL A(1), for example, caused a compiler crash if -fugly-assumed was in effect and A was a local (automatic) array. That case is no longer affected by the new handling of -fugly-assumed.

  * Fix g77 command driver so that g77 -o foo.f no longer deletes foo.f before issuing other diagnostics, and so the -x option is properly handled.

  * Enable inlining of subroutines and functions by the gcc back end. This works as it does for gcc itself---program units may be inlined for invocations that follow them in the same program unit, as long as the appropriate compile-time options are specified.

  * Dummy arguments are no longer assumed to potentially alias (overlap) other dummy arguments or COMMON areas when any of these are defined (assigned to) by Fortran code.

     This can result in faster and/or smaller programs when compiling with optimization enabled, though on some systems this effect is observed only when -fforce-addr also is specified.

     New options -falias-check, -fargument-alias, -fargument-noalias, and -fno-argument-noalias-global control the way g77 handles potential aliasing.

  * The CONJG() and DCONJG() intrinsics now are compiled in-line.

  * The bug-fix for 0.5.19.1 has been re-done. The g77 compiler has been changed back to assume libf2c has no aliasing problems in its implementations of the COMPLEX (and DOUBLE COMPLEX) intrinsics. The libf2c has been changed to have no such problems.

     As a result, 0.5.20 is expected to offer improved performance over 0.5.19.1, perhaps as good as 0.5.19 in most or all cases, due to this change alone.

     Note: This change requires version 0.5.20 of libf2c, at least, when linking code produced by any versions of g77 other than 0.5.19.1. Use g77 -v to determine the version numbers of the libF77, libI77, and libU77 components of the libf2c library. (If these version numbers are not printed---in particular, if the linker complains about unresolved references to names like g77__fvers__---that strongly suggests your installation has an obsolete version of libf2c.)

  * New option -fugly-assign specifies that the same memory locations are to be used to hold the values assigned by both statements I = 3 and ASSIGN 10 TO I, for example. (Normally, g77 uses a separate memory location to hold assigned statement labels.)

  * FORMAT and ENTRY statements now are allowed to precede IMPLICIT NONE statements.

  * Produce diagnostic for unsupported SELECT CASE on CHARACTER type, instead of crashing, at compile time.

  * Fix crashes involving diagnosed or invalid code.

  * Change approach to building libf2c archive (libf2c.a) so that members are added to it only when truly necessary, so the user that installs an already-built g77 doesn't need to have write access to the build tree (whereas the user doing the build might not have access to install new software on the system).

  * Support gcc version 2.7.2.2 (modified by g77 into version 2.7.2.2.f.2), and remove support for prior versions of gcc.

  * Upgrade to libf2c as of 1997-02-08, and fix up some of the build procedures.

  * Improve general build procedures for g77, fixing minor bugs (such as deletion of any file named f771 in the parent directory of gcc/).

  * Enable full support of INTEGER*8 available in libf2c and f2c.h so that f2c users may make full use of its features via the g77 version of f2c.h and the INTEGER*8 support routines in the g77 version of libf2c.

  * Improve g77 driver and libf2c so that g77 -v yields version information on the library.

  * The SNGL and FLOAT intrinsics now are specific intrinsics, instead of synonyms for the generic intrinsic REAL.

  * New intrinsics have been added. These are REALPART, IMAGPART, COMPLEX, LONG, and SHORT.

  * A new group of intrinsics, gnu, has been added to contain the new REALPART, IMAGPART, and COMPLEX intrinsics. An old group, dcp, has been removed.

  * Complain about industry-wide ambiguous references REAL(EXPR) and AIMAG(EXPR), where EXPR is DOUBLE COMPLEX (or any complex type other than COMPLEX), unless -ff90 option specifies Fortran 90 interpretation or new -fugly-complex option, in conjunction with -fnot-f90, specifies f2c interpretation.

  * Make improvements to diagnostics.

  * Speed up compiler a bit.

  * Improvements to documentation and indexing, including a new chapter containing information on one, later more, diagnostics that users are directed to pull up automatically via a message in the diagnostic itself.

     (Hence the menu item M for the node Diagnostics in the top-level menu of the Info documentation.)

In 0.5.19.1:
============

  * Code-generation bugs afflicting operations on complex data have been fixed.

     These bugs occurred when assigning the result of an operation to a complex variable (or array element) that also served as an input to that operation.

     The operations affected by this bug were: CONJG(), DCONJG(), CCOS(), CDCOS(), CLOG(), CDLOG(), CSIN(), CDSIN(), CSQRT(), CDSQRT(), complex division, and raising a DOUBLE COMPLEX operand to an INTEGER power. (The related generic and Z-prefixed intrinsics, such as ZSIN(), also were affected.)

     For example, C = CSQRT(C), Z = Z/C, and Z = Z**I (where C is COMPLEX and Z is DOUBLE COMPLEX) have been fixed.

In 0.5.19:
==========

  * Fix FORMAT statement parsing so negative values for specifiers such as P (e.g. FORMAT(-1PF8.1)) are correctly processed as negative.

  * Fix SIGNAL intrinsic so it once again accepts a procedure as its second argument.

  * A temporary kludge option provides bare-bones information on COMMON and EQUIVALENCE members at debug time.

  * New -fonetrip option specifies FORTRAN-66-style one-trip DO loops.

  * New -fno-silent option causes names of program units to be printed as they are compiled, in a fashion similar to UNIX f77 and f2c.

  * New -fugly-assumed option specifies that arrays dimensioned via DIMENSION X(1), for example, are to be treated as assumed-size.

  * New -fno-typeless-boz option specifies that non-decimal-radix constants using the prefixed-radix form (such as Z'1234') are to be interpreted as INTEGER constants.

  * New -ff66 option is a ``shorthand'' option that specifies behaviors considered appropriate for FORTRAN 66 programs.

  * New -ff77 option is a ``shorthand'' option that specifies behaviors considered appropriate for UNIX f77 programs.

  * New -fugly-comma and -fugly-logint options provided to perform some of what -fugly used to do. -fugly and -fno-ugly are now ``shorthand'' options, in that they do nothing more than enable (or disable) other -fugly-* options.

  * Fix parsing of assignment statements involving targets that are substrings of elements of CHARACTER arrays having names such as READ, WRITE, GOTO, and REALFUNCTIONFOO.

  * Fix crashes involving diagnosed code.

  * Fix handling of local EQUIVALENCE areas so certain cases of valid Fortran programs are not misdiagnosed as improperly extending the area backwards.

  * Support gcc version 2.7.2.1.

  * Upgrade to libf2c as of 1996-09-26, and fix up some of the build procedures.

  * Change code generation for list-directed I/O so it allows for new versions of libf2c that might return non-zero status codes for some operations previously assumed to always return zero.

     This change not only affects how IOSTAT= variables are set by list-directed I/O, it also affects whether END= and ERR= labels are reached by these operations.

  * Add intrinsic support for new FTELL and FSEEK procedures in libf2c.

  * Modify fseek_() in libf2c to be more portable (though, in practice, there might be no systems where this matters) and to catch invalid whence arguments.

  * Some useless warnings from the -Wunused option have been eliminated.

  * Fix a problem building the f771 executable on AIX systems by linking with the -bbigtoc option.

  * Abort configuration if gcc has not been patched using the patch file provided in the gcc/f/gbe/ subdirectory.

  * Add options --help and --version to the g77 command, to conform to GNU coding guidelines. Also add printing of g77 version number when the --verbose (-v) option is used.

  * Change internally generated name for local EQUIVALENCE areas to one based on the alphabetically sorted first name in the list of names for entities placed at the beginning of the areas.

  * Improvements to documentation and indexing.

In 0.5.18:
==========

  * Add some rudimentary support for INTEGER*1, INTEGER*2, INTEGER*8, and their LOGICAL equivalents. (This support works on most, maybe all, gcc targets.)

     Thanks to Scott Snyder (snyder@d0sgif.fnal.gov) for providing the patch for this!

     Among the missing elements from the support for these features are full intrinsic support and constants.

  * Add some rudimentary support for the BYTE and WORD type-declaration statements. BYTE corresponds to INTEGER*1, while WORD corresponds to INTEGER*2.

     Thanks to Scott Snyder (snyder@d0sgif.fnal.gov) for providing the patch for this!

  * The compiler code handling intrinsics has been largely rewritten to accommodate the new types. No new intrinsics or arguments for existing intrinsics have been added, so there is, at this point, no intrinsic to convert to INTEGER*8, for example.

  * Support automatic arrays in procedures.

  * Reduce space/time requirements for handling large sparsely initialized aggregate arrays. This improvement applies to only a subset of the general problem to be addressed in 0.6.

  * Treat initial values of zero as if they weren't specified (in DATA and type-declaration statements). The initial values will be set to zero anyway, but the amount of compile time processing them will be reduced, in some cases significantly (though, again, this is only a subset of the general problem to be addressed in 0.6).

     A new option, -fzeros, is introduced to enable the traditional treatment of zeros as any other value.

  * With -ff90 in force, g77 incorrectly interpreted REAL(Z) as returning a REAL result, instead of as a DOUBLE PRECISION result. (Here, Z is DOUBLE COMPLEX.)

     With -fno-f90 in force, the interpretation remains unchanged, since this appears to be how at least some F77 code using the DOUBLE COMPLEX extension expected it to work.

     Essentially, REAL(Z) in F90 is the same as DBLE(Z), while in extended F77, it appears to be the same as REAL(REAL(Z)).

  * An expression involving exponentiation, where both operands were type INTEGER and the right-hand operand was negative, was erroneously evaluated.

  * Fix bugs involving DATA implied-DO constructs (these involved an errant diagnostic and a crash, both on good code, one involving subsequent statement-function definition).

  * Close INCLUDE files after processing them, so compiling source files with lots of INCLUDE statements does not result in being unable to open INCLUDE files after all the available file descriptors are used up.

  * Speed up compiling, especially of larger programs, and perhaps slightly reduce memory utilization while compiling (this is not the improvement planned for 0.6 involving large aggregate areas)---these improvements result from simply turning off some low-level code to do self-checking that hasn't been triggered in a long time.

  * Introduce three new options that implement optimizations in the gcc back end (GBE). These options are -fmove-all-movables, -freduce-all-givs, and -frerun-loop-opt, which are enabled, by default, for Fortran compilations. These optimizations are intended to help toon Fortran programs.

  * Patch the GBE to do a better job optimizing certain kinds of references to array elements.

  * Due to patches to the GBE, the version number of gcc also is patched to make it easier to manage installations, especially useful if it turns out a g77 change to the GBE has a bug.

     The g77-modified version number is the gcc version number with the string .f.N appended, where f identifies the version as enhanced for Fortran, and N is 1 for the first Fortran patch for that version of gcc, 2 for the second, and so on.

     So, this introduces version 2.7.2.f.1 of gcc.

  * Make several improvements and fixes to diagnostics, including the removal of two that were inappropriate or inadequate.

  * Warning about two successive arithmetic operators, produced by -Wsurprising, now produced only when both operators are, indeed, arithmetic (not relational/boolean).

  * -Wsurprising now warns about the remaining cases of using non-integral variables for implied-DO loops, instead of these being rejected unless -fpedantic or -fugly specified.

  * Allow SAVE of a local variable or array, even after it has been given an initial value via DATA, for example.

  * Introduce an Info version of g77 documentation, which supercedes gcc/f/CREDITS, gcc/f/DOC, and gcc/f/PROJECTS. These files will be removed in a future release. The files gcc/f/BUGS, gcc/f/INSTALL, and gcc/f/NEWS now are automatically built from the texinfo source when distributions are made.

     This effort was inspired by a first pass at translating g77-0.5.16/f/DOC that was contributed to Craig by David Ronis (ronis@onsager.chem.mcgill.ca).

  * New -fno-second-underscore option to specify that, when -funderscoring is in effect, a second underscore is not to be appended to Fortran names already containing an underscore.

  * Change the way iterative DO loops work to follow the F90 standard. In particular, calculation of the iteration count is still done by converting the start, end, and increment parameters to the type of the DO variable, but the result of the calculation is always converted to the default INTEGER type.

     (This should have no effect on existing code compiled by g77, but code written to assume that use of a wider type for the DO variable will result in an iteration count being fully calculated using that wider type (wider than default INTEGER) must be rewritten.)

  * Support gcc version 2.7.2.

  * Upgrade to libf2c as of 1996-03-23, and fix up some of the build procedures.

     Note that the email addresses related to f2c have changed---the distribution site now is named netlib.bell-labs.com, and the maintainer's new address is dmg@bell-labs.com.

In 0.5.17:
==========

  * Fix serious bug in g77 -v command that can cause removal of a system's /dev/null special file if run by user root.

     All users of version 0.5.16 should ensure that they have not removed /dev/null or replaced it with an ordinary file (e.g. by comparing the output of ls -l /dev/null with ls -l /dev/zero. If the output isn't basically the same, contact your system administrator about restoring /dev/null to its proper status).

     This bug is particularly insidious because removing /dev/null as a special file can go undetected for quite a while, aside from various applications and programs exhibiting sudden, strange behaviors.

     I sincerely apologize for not realizing the implications of the fact that when g77 -v runs the ld command with -o /dev/null that ld tries to remove the executable it is supposed to build (especially if it reports unresolved references, which it should in this case)!

  * Fix crash on CHARACTER*(*) FOO in a main or block data program unit.

  * Fix crash that can occur when diagnostics given outside of any program unit (such as when input file contains @foo).

  * Fix crashes, infinite loops (hangs), and such involving diagnosed code.

  * Fix ASSIGN'ed variables so they can be SAVE'd or dummy arguments, and issue clearer error message in cases where target of ASSIGN or ASSIGNed GOTO/FORMAT is too small (which should never happen).

  * Make libf2c build procedures work on more systems again by eliminating unnecessary invocations of ld -r -x and mv.

  * Fix omission of -funix-intrinsics-... options in list of permitted options to compiler.

  * Fix failure to always diagnose missing type declaration for IMPLICIT NONE.

  * Fix compile-time performance problem (which could sometimes crash the compiler, cause a hang, or whatever, due to a bug in the back end) involving exponentiation with a large INTEGER constant for the right-hand operator (e.g. I**32767).

  * Fix build procedures so cross-compiling g77 (the fini utility in particular) is properly built using the host compiler.

  * Add new -Wsurprising option to warn about constructs that are interpreted by the Fortran standard (and g77) in ways that are surprising to many programmers.

  * Add ERF() and ERFC() as generic intrinsics mapping to existing ERF/DERF and ERFC/DERFC specific intrinsics.

     Note: You should specify INTRINSIC ERF,ERFC in any code where you might use these as generic intrinsics, to improve likelihood of diagnostics (instead of subtle run-time bugs) when using a compiler that doesn't support these as intrinsics (e.g. f2c).

  * Remove from -fno-pedantic the diagnostic about DO with non-INTEGER index variable; issue that under -Wsurprising instead.

  * Clarify some diagnostics that say things like ``ignored'' when that's misleading.

  * Clarify diagnostic on use of .EQ./.NE. on LOGICAL operands.

  * Minor improvements to code generation for various operations on LOGICAL operands.

  * Minor improvement to code generation for some DO loops on some machines.

  * Support gcc version 2.7.1.

  * Upgrade to libf2c as of 1995-11-15.

In 0.5.16:
==========

  * Fix a code-generation bug involving complicated EQUIVALENCE statements not involving COMMON.

  * Fix code-generation bugs involving invoking ``gratis'' library procedures in libf2c from code compiled with -fno-f2c by making these procedures known to g77 as intrinsics (not affected by -fno-f2c). This is known to fix code invoking ERF(), ERFC(), DERF(), and DERFC().

  * Update libf2c to include netlib patches through 1995-08-16, and #define WANT_LEAD_0 to 1 to make g77-compiled code more consistent with other Fortran implementations by outputting leading zeros in formatted and list-directed output.

  * Fix a code-generation bug involving adjustable dummy arrays with high bounds whose primaries are changed during procedure execution, and which might well improve code-generation performance for such arrays compared to f2c plus gcc (but apparently only when using gcc-2.7.0 or later).

  * Fix a code-generation bug involving invocation of COMPLEX and DOUBLE COMPLEX FUNCTIONs and doing COMPLEX and DOUBLE COMPLEX divides, when the result of the invocation or divide is assigned directly to a variable that overlaps one or more of the arguments to the invocation or divide.

  * Fix crash by not generating new optimal code for X**I if I is nonconstant and the expression is used to dimension a dummy array, since the gcc back end does not support the necessary mechanics (and the gcc front end rejects the equivalent construct, as it turns out).

  * Fix crash on expressions like COMPLEX**INTEGER.

  * Fix crash on expressions like (1D0,2D0)**2, i.e. raising a DOUBLE COMPLEX constant to an INTEGER constant power.

  * Fix crashes and such involving diagnosed code.

  * Diagnose, instead of crashing on, statement function definitions having duplicate dummy argument names.

  * Fix bug causing rejection of good code involving statement function definitions.

  * Fix bug resulting in debugger not knowing size of local equivalence area when any member of area has initial value (via DATA, for example).

  * Fix installation bug that prevented installation of g77 driver. Provide for easy selection of whether to install copy of g77 as f77 to replace the broken code.

  * Fix gcc driver (affects g77 thereby) to not gratuitously invoke the f771 program (e.g. when -E is specified).

  * Fix diagnostic to point to correct source line when it immediately follows an INCLUDE statement.

  * Support more compiler options in gcc/g77 when compiling Fortran files. These options include -p, -pg, -aux-info, -P, correct setting of version-number macros for preprocessing, full recognition of -O0, and automatic insertion of configuration-specific linker specs.

  * Add new intrinsics that interface to existing routines in libf2c: ABORT, DERF, DERFC, ERF, ERFC, EXIT, FLUSH, GETARG, GETENV, IARGC, SIGNAL, and SYSTEM. Note that ABORT, EXIT, FLUSH, SIGNAL, and SYSTEM are intrinsic subroutines, not functions (since they have side effects), so to get the return values from SIGNAL and SYSTEM, append a final argument specifying an INTEGER variable or array element (e.g. CALL SYSTEM('rm foo',ISTAT)).

  * Add new intrinsic group named unix to contain the new intrinsics, and by default enable this new group.

  * Move LOC() intrinsic out of the vxt group to the new unix group.

  * Improve g77 so that g77 -v by itself (or with certain other options, including -B, -b, -i, -nostdlib, and -V) reports lots more useful version info, and so that long-form options gcc accepts are understood by g77 as well (even in truncated, unambiguous forms).

  * Add new g77 option --driver=name to specify driver when default, gcc, isn't appropriate.

  * Add support for # directives (as output by the preprocessor) in the compiler, and enable generation of those directives by the preprocessor (when compiling .F files) so diagnostics and debugging info are more useful to users of the preprocessor.

  * Produce better diagnostics, more like gcc, with info such as In function `foo': and In file included from...:.

  * Support gcc's -fident and -fno-ident options.

  * When -Wunused in effect, don't warn about local variables used as statement-function dummy arguments or DATA implied-DO iteration variables, even though, strictly speaking, these are not uses of the variables themselves.

  * When -W -Wunused in effect, don't warn about unused dummy arguments at all, since there's no way to turn this off for individual cases (g77 might someday start warning about these)---applies to gcc versions 2.7.0 and later, since earlier versions didn't warn about unused dummy arguments.

  * New option -fno-underscoring that inhibits transformation of names (by appending one or two underscores) so users may experiment with implications of such an environment.

  * Minor improvement to gcc/f/info module to make it easier to build g77 using the native (non-gcc) compiler on certain machines (but definitely not all machines nor all non-gcc compilers). Please do not report bugs showing problems compilers have with macros defined in gcc/f/target.h and used in places like gcc/f/expr.c.

  * Add warning to be printed for each invocation of the compiler if the target machine INTEGER, REAL, or LOGICAL size is not 32 bits, since g77 is known to not work well for such cases (to be fixed in Version 0.6---see Actual Bugs We Haven't Fixed Yet).

  * Lots of new documentation (though work is still needed to put it into canonical GNU format).

  * Build libf2c with -g0, not -g2, in effect (by default), to produce smaller library without lots of debugging clutter.

In 0.5.15:
==========

  * Fix bad code generation involving X**I and temporary, internal variables generated by g77 and the back end (such as for DO loops).

  * Fix crash given CHARACTER A;DATA A/.TRUE./.

  * Replace crash with diagnostic given CHARACTER A;DATA A/1.0/.

  * Fix crash or other erratic behavior when null character constant ('') is encountered.

  * Fix crash or other erratic behavior involving diagnosed code.

  * Fix code generation for external functions returning type REAL when the -ff2c option is in force (which it is by default) so that f2c compatibility is indeed provided.

  * Disallow COMMON I(10) if I has previously been specified with an array declarator.

  * New -ffixed-line-length-N option, where N is the maximum length of a typical fixed-form line, defaulting to 72 columns, such that characters beyond column N are ignored, or N is none, meaning no characters are ignored. does not affect lines with & in column 1, which are always processed as if -ffixed-line-length-none was in effect.

  * No longer generate better code for some kinds of array references, as gcc back end is to be fixed to do this even better, and it turned out to slow down some code in some cases after all.

  * In COMMON and EQUIVALENCE areas with any members given initial values (e.g. via DATA), uninitialized members now always initialized to binary zeros (though this is not required by the standard, and might not be done in future versions of g77). Previously, in some COMMON/EQUIVALENCE areas (essentially those with members of more than one type), the uninitialized members were initialized to spaces, to cater to CHARACTER types, but it seems no existing code expects that, while much existing code expects binary zeros.

In 0.5.14:
==========

  * Don't emit bad code when low bound of adjustable array is nonconstant and thus might vary as an expression at run time.

  * Emit correct code for calculation of number of trips in DO loops for cases where the loop should not execute at all. (This bug affected cases where the difference between the begin and end values was less than the step count, though probably not for floating-point cases.)

  * Fix crash when extra parentheses surround item in DATA implied-DO list.

  * Fix crash over minor internal inconsistencies in handling diagnostics, just substitute dummy strings where necessary.

  * Fix crash on some systems when compiling call to MVBITS() intrinsic.

  * Fix crash on array assignment TYPEDDD(...)=..., where DDD is a string of one or more digits.

  * Fix crash on DCMPLX() with a single INTEGER argument.

  * Fix various crashes involving code with diagnosed errors.

  * Support -I option for INCLUDE statement, plus gcc's header.gcc facility for handling systems like MS-DOS.

  * Allow INCLUDE statement to be continued across multiple lines, even allow it to coexist with other statements on the same line.

  * Incorporate Bellcore fixes to libf2c through 1995-03-15---this fixes a bug involving infinite loops reading EOF with empty list-directed I/O list.

  * Remove all the g77-specific auto-configuration scripts, code, and so on, except for temporary substitutes for bsearch() and strtoul(), as too many configure/build problems were reported in these areas. People will have to fix their systems' problems themselves, or at least somewhere other than g77, which expects a working ANSI C environment (and, for now, a GNU C compiler to compile g77 itself).

  * Complain if initialized common redeclared as larger in subsequent program unit.

  * Warn if blank common initialized, since its size can vary and hence related warnings that might be helpful won't be seen.

  * New -fbackslash option, on by default, that causes \ within CHARACTER and Hollerith constants to be interpreted a la GNU C. Note that this behavior is somewhat different from f2c's, which supports only a limited subset of backslash (escape) sequences.

  * Make -fugly-args the default.

  * New -fugly-init option, on by default, that allows typeless/Hollerith to be specified as initial values for variables or named constants (PARAMETER), and also allows character<->numeric conversion in those contexts---turn off via -fno-ugly-init.

  * New -finit-local-zero option to initialize local variables to binary zeros. This does not affect whether they are SAVEd, i.e. made automatic or static.

  * New -Wimplicit option to warn about implicitly typed variables, arrays, and functions. (Basically causes all program units to default to IMPLICIT NONE.)

  * -Wall now implies -Wuninitialized as with gcc (i.e. unless -O not specified, since -Wuninitialized requires -O), and implies -Wunused as well.

  * -Wunused no longer gives spurious messages for unused EXTERNAL names (since they are assumed to refer to block data program units, to make use of libraries more reliable).

  * Support %LOC() and LOC() of character arguments.

  * Support null (zero-length) character constants and expressions.

  * Support f2c's IMAG() generic intrinsic.

  * Support ICHAR(), IACHAR(), and LEN() of character expressions that are valid in assignments but not normally as actual arguments.

  * Support f2c-style & in column 1 to mean continuation line.

  * Allow NAMELIST, EXTERNAL, INTRINSIC, and VOLATILE in BLOCK DATA, even though these are not allowed by the standard.

  * Allow RETURN in main program unit.

  * Changes to Hollerith-constant support to obey Appendix C of the standard:

       -- Now padded on the right with zeros, not spaces.

       -- Hollerith ``format specifications'' in the form of arrays of non-character allowed.

       -- Warnings issued when non-space truncation occurs when converting to another type.

       -- When specified as actual argument, now passed by reference to INTEGER (padded on right with spaces if constant too small, otherwise fully intact if constant wider the INTEGER type) instead of by value.

     Warning: f2c differs on the interpretation of CALL FOO(1HX), which it treats exactly the same as CALL FOO('X'), but which the standard and g77 treat as CALL FOO(%REF('X   ')) (padded with as many spaces as necessary to widen to INTEGER), essentially.

  * Changes and fixes to typeless-constant support:

       -- Now treated as a typeless double-length INTEGER value.

       -- Warnings issued when overflow occurs.

       -- Padded on the left with zeros when converting to a larger type.

       -- Should be properly aligned and ordered on the target machine for whatever type it is turned into.

       -- When specified as actual argument, now passed as reference to a default INTEGER constant.

  * %DESCR() of a non-CHARACTER expression now passes a pointer to the expression plus a length for the expression just as if it were a CHARACTER expression. For example, CALL FOO(%DESCR(D)), where D is REAL*8, is the same as CALL FOO(D,%VAL(8))).

  * Name of multi-entrypoint master function changed to incorporate the name of the primary entry point instead of a decimal value, so the name of the master function for SUBROUTINE X with alternate entry points is now __g77_masterfun_x.

  * Remove redundant message about zero-step-count DO loops.

  * Clean up diagnostic messages, shortening many of them.

  * Fix typo in g77 man page.

  * Clarify implications of constant-handling bugs in f/BUGS.

  * Generate better code for ** operator with a right-hand operand of type INTEGER.

  * Generate better code for SQRT() and DSQRT(), also when -ffast-math specified, enable better code generation for SIN() and COS().

  * Generate better code for some kinds of array references.

  * Speed up lexing somewhat (this makes the compilation phase noticeably faster).