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diff --git a/contrib/gcc/f/BUGS b/contrib/gcc/f/BUGS new file mode 100644 index 0000000..acfe4ab --- /dev/null +++ b/contrib/gcc/f/BUGS @@ -0,0 +1,130 @@ +_Note:_ This file is automatically generated from the files +`bugs0.texi' and `bugs.texi'. `BUGS' is _not_ a source file, although +it is normally included within source distributions. + + This file lists known bugs in the GCC-3.2 version of the GNU Fortran +compiler. Copyright (C) 1995,1996,1997,1998,1999,2000,2001,2002 Free +Software Foundation, Inc. You may copy, distribute, and modify it +freely as long as you preserve this copyright notice and permission +notice. + +Known Bugs In GNU Fortran +************************* + + This section identifies bugs that `g77' _users_ might run into in +the GCC-3.2 version of `g77'. This includes bugs that are actually in +the `gcc' back end (GBE) or in `libf2c', because those sets of code are +at least somewhat under the control of (and necessarily intertwined +with) `g77', so it isn't worth separating them out. + + For information on bugs in _other_ versions of `g77', see +`gcc/gcc/f/NEWS'. There, lists of bugs fixed in various versions of +`g77' can help determine what bugs existed in prior versions. + + An online, "live" version of this document (derived directly from +the mainline, development version of `g77' within `gcc') is available +via `http://www.gnu.org/software/gcc/onlinedocs/g77/Trouble.html'. +Follow the "Known Bugs" link. + + The following information was last updated on 2002-02-01: + + * `g77' fails to warn about use of a "live" iterative-DO variable as + an implied-DO variable in a `WRITE' or `PRINT' statement (although + it does warn about this in a `READ' statement). + + * Something about `g77''s straightforward handling of label + references and definitions sometimes prevents the GBE from + unrolling loops. Until this is solved, try inserting or removing + `CONTINUE' statements as the terminal statement, using the `END DO' + form instead, and so on. + + * Some confusion in diagnostics concerning failing `INCLUDE' + statements from within `INCLUDE''d or `#include''d files. + + * `g77' assumes that `INTEGER(KIND=1)' constants range from `-2**31' + to `2**31-1' (the range for two's-complement 32-bit values), + instead of determining their range from the actual range of the + type for the configuration (and, someday, for the constant). + + Further, it generally doesn't implement the handling of constants + very well in that it makes assumptions about the configuration + that it no longer makes regarding variables (types). + + Included with this item is the fact that `g77' doesn't recognize + that, on IEEE-754/854-compliant systems, `0./0.' should produce a + NaN and no warning instead of the value `0.' and a warning. + + * `g77' uses way too much memory and CPU time to process large + aggregate areas having any initialized elements. + + For example, `REAL A(1000000)' followed by `DATA A(1)/1/' takes up + way too much time and space, including the size of the generated + assembler file. + + Version 0.5.18 improves cases like this--specifically, cases of + _sparse_ initialization that leave large, contiguous areas + uninitialized--significantly. However, even with the + improvements, these cases still require too much memory and CPU + time. + + (Version 0.5.18 also improves cases where the initial values are + zero to a much greater degree, so if the above example ends with + `DATA A(1)/0/', the compile-time performance will be about as good + as it will ever get, aside from unrelated improvements to the + compiler.) + + Note that `g77' does display a warning message to notify the user + before the compiler appears to hang. + + * When debugging, after starting up the debugger but before being + able to see the source code for the main program unit, the user + must currently set a breakpoint at `MAIN__' (or `MAIN___' or + `MAIN_' if `MAIN__' doesn't exist) and run the program until it + hits the breakpoint. At that point, the main program unit is + activated and about to execute its first executable statement, but + that's the state in which the debugger should start up, as is the + case for languages like C. + + * Debugging `g77'-compiled code using debuggers other than `gdb' is + likely not to work. + + Getting `g77' and `gdb' to work together is a known + problem--getting `g77' to work properly with other debuggers, for + which source code often is unavailable to `g77' developers, seems + like a much larger, unknown problem, and is a lower priority than + making `g77' and `gdb' work together properly. + + On the other hand, information about problems other debuggers have + with `g77' output might make it easier to properly fix `g77', and + perhaps even improve `gdb', so it is definitely welcome. Such + information might even lead to all relevant products working + together properly sooner. + + * `g77' doesn't work perfectly on 64-bit configurations such as the + Digital Semiconductor ("DEC") Alpha. + + This problem is largely resolved as of version 0.5.23. + + * `g77' currently inserts needless padding for things like `COMMON + A,IPAD' where `A' is `CHARACTER*1' and `IPAD' is `INTEGER(KIND=1)' + on machines like x86, because the back end insists that `IPAD' be + aligned to a 4-byte boundary, but the processor has no such + requirement (though it is usually good for performance). + + The `gcc' back end needs to provide a wider array of + specifications of alignment requirements and preferences for + targets, and front ends like `g77' should take advantage of this + when it becomes available. + + * The `libf2c' routines that perform some run-time arithmetic on + `COMPLEX' operands were modified circa version 0.5.20 of `g77' to + work properly even in the presence of aliased operands. + + While the `g77' and `netlib' versions of `libf2c' differ on how + this is accomplished, the main differences are that we believe the + `g77' version works properly even in the presence of _partially_ + aliased operands. + + However, these modifications have reduced performance on targets + such as x86, due to the extra copies of operands involved. + |