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diff --git a/contrib/gcc/f/INSTALL b/contrib/gcc/f/INSTALL new file mode 100644 index 0000000..9185880 --- /dev/null +++ b/contrib/gcc/f/INSTALL @@ -0,0 +1,352 @@ +*Note:* This file is automatically generated from the files +`install0.texi' and `g77install.texi'. `INSTALL' is *not* a source +file, although it is normally included within source distributions. + + This file contains installation information for the GNU Fortran +compiler. Copyright (C) {No Value For "copyrights-install"} Free +Software Foundation, Inc. You may copy, distribute, and modify it +freely as long as you preserve this copyright notice and permission +notice. + +Installing GNU Fortran +********************** + + The following information describes how to install `g77'. + + Note that, for users of the GCC-2.95 version of `g77', much of the +information is obsolete, and is superceded by the GCC installation +procedures. Such information is accordingly omitted and flagged as +such. + + *Warning:* The information below is still under development, and +might not accurately reflect the `g77' code base of which it is a part. +Efforts are made to keep it somewhat up-to-date, but they are +particularly concentrated on any version of this information that is +distributed as part of a *released* `g77'. + + In particular, while this information is intended to apply to the +GCC-2.95 version of `g77', only an official *release* of that version +is expected to contain documentation that is most consistent with the +`g77' product in that version. + + The following information was last updated on 1999-07-17: + +Prerequisites +============= + + For users of the GCC-2.95 version of `g77', this information is +superceded by the GCC installation instructions. + +Problems Installing +=================== + + This is a list of problems (and some apparent problems which don't +really mean anything is wrong) that show up when configuring, building, +installing, or porting GNU Fortran. + + *Note Installation Problems: (gcc)Installation Problems, for more +information on installation problems that can afflict either `gcc' or +`g77'. + +General Problems +---------------- + + These problems can occur on most or all systems. + +GNU C Required +.............. + + Compiling `g77' requires GNU C, not just ANSI C. Fixing this +wouldn't be very hard (just tedious), but the code using GNU extensions +to the C language is expected to be rewritten for 0.6 anyway, so there +are no plans for an interim fix. + + This requirement does not mean you must already have `gcc' installed +to build `g77'. As long as you have a working C compiler, you can use a +"bootstrap" build to automate the process of first building `gcc' using +the working C compiler you have, then building `g77' and rebuilding +`gcc' using that just-built `gcc', and so on. + +Patching GNU CC +............... + + `g77' no longer requires application of a patch file to the `gcc' +compiler tree. In fact, no such patch file is distributed with `g77'. +This is as of version 0.5.23 and `egcs' version 1.0. + +Building GNU CC Necessary +......................... + + It should be possible to build the runtime without building `cc1' +and other non-Fortran items, but, for now, an easy way to do that is +not yet established. + +Missing strtoul or bsearch +.......................... + + This information does not apply to the GCC-2.95 version of `g77', + +Cleanup Kills Stage Directories +............................... + + It'd be helpful if `g77''s `Makefile.in' or `Make-lang.in' would +create the various `stageN' directories and their subdirectories, so +developers and expert installers wouldn't have to reconfigure after +cleaning up. + + That help has arrived as of version 0.5.23 of `g77' and version 1.1 +of `egcs'. Configuration itself no longer creates any particular +directories that are unique to `g77'. The build procedures in +`Make-lang.in' take care of that, on demand. + +LANGUAGES Macro Ignored +....................... + + Prior to version 0.5.23 of `g77' and version 1.1 of `egcs', `g77' +would sometimes ignore the absence of `f77' and `F77' in the +`LANGUAGES' macro definition used for the `make' command being +processed. + + As of `g77' version 0.5.23 and `egcs' version 1.1, `g77' now obeys +this macro in all relevant situations. + + However, in versions of `gcc' through 2.8.1, non-`g77' portions of +`gcc', such as `g++', are known to go ahead and perform various +language-specific activities when their respective language strings do +not appear in the `LANGUAGES' macro in effect during that invocation of +`make'. + + It is expected that these remaining problems will be fixed in a +future version of `gcc'. + +System-specific Problems +------------------------ + + A linker bug on some versions of AIX 4.1 might prevent building when +`g77' is built within `gcc'. It might also occur when building within +`egcs'. + +Cross-compiler Problems +----------------------- + + `g77' has been in alpha testing since September of 1992, and in +public beta testing since February of 1995. Alpha testing was done by +a small number of people worldwide on a fairly wide variety of +machines, involving self-compilation in most or all cases. Beta +testing has been done primarily via self-compilation, but in more and +more cases, cross-compilation (and "criss-cross compilation", where a +version of a compiler is built on one machine to run on a second and +generate code that runs on a third) has been tried and has succeeded, +to varying extents. + + Generally, `g77' can be ported to any configuration to which `gcc', +`f2c', and `libf2c' can be ported and made to work together, aside from +the known problems described in this manual. If you want to port `g77' +to a particular configuration, you should first make sure `gcc' and +`libf2c' can be ported to that configuration before focusing on `g77', +because `g77' is so dependent on them. + + Even for cases where `gcc' and `libf2c' work, you might run into +problems with cross-compilation on certain machines, for several +reasons. + + * There is one known bug (a design bug to be fixed in 0.6) that + prevents configuration of `g77' as a cross-compiler in some cases, + though there are assumptions made during configuration that + probably make doing non-self-hosting builds a hassle, requiring + manual intervention. + + * `gcc' might still have some trouble being configured for certain + combinations of machines. For example, it might not know how to + handle floating-point constants. + + * Improvements to the way `libg2c' is built could make building + `g77' as a cross-compiler easier--for example, passing and using + `$(LD)' and `$(AR)' in the appropriate ways. (This is improved in + the `egcs' version of `g77', especially as of version 1.1.) + + * There are still some challenges putting together the right + run-time libraries (needed by `libg2c') for a target system, + depending on the systems involved in the configuration. (This is + a general problem with cross-compilation, and with `gcc' in + particular.) + +Changing Settings Before Building +================================= + + Here are some internal `g77' settings that can be changed by editing +source files in `egcs/gcc/f/' before building. + + This information, and perhaps even these settings, represent +stop-gap solutions to problems people doing various ports of `g77' have +encountered. As such, none of the following information is expected to +be pertinent in future versions of `g77'. + +Larger File Unit Numbers +------------------------ + + As distributed, whether as part of `f2c' or `g77', `libf2c' accepts +file unit numbers only in the range 0 through 99. For example, a +statement such as `WRITE (UNIT=100)' causes a run-time crash in +`libf2c', because the unit number, 100, is out of range. + + If you know that Fortran programs at your installation require the +use of unit numbers higher than 99, you can change the value of the +`MXUNIT' macro, which represents the maximum unit number, to an +appropriately higher value. + + To do this, edit the file `egcs/libf2c/libI77/fio.h' in your `g77' +source tree, changing the following line: + + #define MXUNIT 100 + + Change the line so that the value of `MXUNIT' is defined to be at +least one *greater* than the maximum unit number used by the Fortran +programs on your system. + + (For example, a program that does `WRITE (UNIT=255)' would require +`MXUNIT' set to at least 256 to avoid crashing.) + + Then build or rebuild `g77' as appropriate. + + *Note:* Changing this macro has *no* effect on other limits your +system might place on the number of files open at the same time. That +is, the macro might allow a program to do `WRITE (UNIT=100)', but the +library and operating system underlying `libf2c' might disallow it if +many other files have already been opened (via `OPEN' or implicitly via +`READ', `WRITE', and so on). Information on how to increase these +other limits should be found in your system's documentation. + +Always Flush Output +------------------- + + Some Fortran programs require output (writes) to be flushed to the +operating system (under UNIX, via the `fflush()' library call) so that +errors, such as disk full, are immediately flagged via the relevant +`ERR=' and `IOSTAT=' mechanism, instead of such errors being flagged +later as subsequent writes occur, forcing the previously written data +to disk, or when the file is closed. + + Essentially, the difference can be viewed as synchronous error +reporting (immediate flagging of errors during writes) versus +asynchronous, or, more precisely, buffered error reporting (detection +of errors might be delayed). + + `libg2c' supports flagging write errors immediately when it is built +with the `ALWAYS_FLUSH' macro defined. This results in a `libg2c' that +runs slower, sometimes quite a bit slower, under certain +circumstances--for example, accessing files via the networked file +system NFS--but the effect can be more reliable, robust file I/O. + + If you know that Fortran programs requiring this level of precision +of error reporting are to be compiled using the version of `g77' you +are building, you might wish to modify the `g77' source tree so that +the version of `libg2c' is built with the `ALWAYS_FLUSH' macro defined, +enabling this behavior. + + To do this, find this line in `egcs/libf2c/f2c.h' in your `g77' +source tree: + + /* #define ALWAYS_FLUSH */ + + Remove the leading `/* ', so the line begins with `#define', and the +trailing ` */'. + + Then build or rebuild `g77' as appropriate. + +Maximum Stackable Size +---------------------- + + `g77', on most machines, puts many variables and arrays on the stack +where possible, and can be configured (by changing +`FFECOM_sizeMAXSTACKITEM' in `egcs/gcc/f/com.c') to force smaller-sized +entities into static storage (saving on stack space) or permit +larger-sized entities to be put on the stack (which can improve +run-time performance, as it presents more opportunities for the GBE to +optimize the generated code). + + *Note:* Putting more variables and arrays on the stack might cause +problems due to system-dependent limits on stack size. Also, the value +of `FFECOM_sizeMAXSTACKITEM' has no effect on automatic variables and +arrays. *Note But-bugs::, for more information. + +Floating-point Bit Patterns +--------------------------- + + The `g77' build will crash if an attempt is made to build it as a +cross-compiler for a target when `g77' cannot reliably determine the +bit pattern of floating-point constants for the target. Planned +improvements for version 0.6 of `g77' will give it the capabilities it +needs to not have to crash the build but rather generate correct code +for the target. (Currently, `g77' would generate bad code under such +circumstances if it didn't crash during the build, e.g. when compiling +a source file that does something like `EQUIVALENCE (I,R)' and `DATA +R/9.43578/'.) + +Initialization of Large Aggregate Areas +--------------------------------------- + + A warning message is issued when `g77' sees code that provides +initial values (e.g. via `DATA') to an aggregate area (`COMMON' or +`EQUIVALENCE', or even a large enough array or `CHARACTER' variable) +that is large enough to increase `g77''s compile time by roughly a +factor of 10. + + This size currently is quite small, since `g77' currently has a +known bug requiring too much memory and time to handle such cases. In +`egcs/gcc/f/data.c', the macro `FFEDATA_sizeTOO_BIG_INIT_' is defined +to the minimum size for the warning to appear. The size is specified +in storage units, which can be bytes, words, or whatever, on a +case-by-case basis. + + After changing this macro definition, you must (of course) rebuild +and reinstall `g77' for the change to take effect. + + Note that, as of version 0.5.18, improvements have reduced the scope +of the problem for *sparse* initialization of large arrays, especially +those with large, contiguous uninitialized areas. However, the warning +is issued at a point prior to when `g77' knows whether the +initialization is sparse, and delaying the warning could mean it is +produced too late to be helpful. + + Therefore, the macro definition should not be adjusted to reflect +sparse cases. Instead, adjust it to generate the warning when densely +initialized arrays begin to cause responses noticeably slower than +linear performance would suggest. + +Alpha Problems Fixed +-------------------- + + `g77' used to warn when it was used to compile Fortran code for a +target configuration that is not basically a 32-bit machine (such as an +Alpha, which is a 64-bit machine, especially if it has a 64-bit +operating system running on it). That was because `g77' was known to +not work properly on such configurations. + + As of version 0.5.20, `g77' is believed to work well enough on such +systems. So, the warning is no longer needed or provided. + + However, support for 64-bit systems, especially in areas such as +cross-compilation and handling of intrinsics, is still incomplete. The +symptoms are believed to be compile-time diagnostics rather than the +generation of bad code. It is hoped that version 0.6 will completely +support 64-bit systems. + +Quick Start +=========== + + For users of the GCC-2.95 version of `g77', this information is +superceded by the GCC installation instructions. + +Complete Installation +===================== + + For users of the GCC-2.95 version of `g77', this information is +superceded by the GCC installation instructions. + +Distributing Binaries +===================== + + For users of the GCC-2.95 version of `g77', this information is +superceded by the GCC installation instructions. + |
