news

gcc-2.95.3 Linux下最常用的C编译器

*Note:* This file is automatically generated from the files
`news0.texi' and `news.texi'.  `NEWS' is *not* a source file, although
it is normally included within source distributions.

   This file lists news about the GCC-2.95 version (and some other
versions) of the GNU Fortran compiler.  Copyright (C) 1995-1999 Free
Software Foundation, Inc.  You may copy, distribute, and modify it
freely as long as you preserve this copyright notice and permission
notice.

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.

   *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.

   Nevertheless, information on *previous* releases of `g77', below, is
likely to be more up-to-date and accurate than the equivalent
information that accompanied those releases, assuming the last-updated
date of the information below is later than the dates of those releases.

   That's due to attempts to keep this development version of news
about previous `g77' versions up-to-date.

   An online, "live" version of this document (derived directly from
the mainline, development version of `g77' within `egcs') is available
at `http://www.gnu.org/software/gcc/onlinedocs/g77_news.html'.

   The following information was last updated on 1999-07-08:

In 0.5.25, `GCC' 2.95 (`EGCS' 1.2) versus `EGCS' 1.1.2:
=======================================================

  1. `g77' no longer generates bad code for assignments, or other
     conversions, of `REAL' or `COMPLEX' constant expressions to type
     `INTEGER(KIND=2)' (often referred to as `INTEGER*8').

     For example, `INTEGER*8 J; J = 4E10' now works as documented.

  2. `g77' no longer truncates `INTEGER(KIND=2)' (usually `INTEGER*8')
     subscript expressions when evaluating array references on systems
     with pointers widers than `INTEGER(KIND=1)' (such as Alphas).

  3. `g77' no longer generates bad code for an assignment to a
     `COMPLEX' variable or array that partially overlaps one or more of
     the sources of the same assignment (a very rare construction).  It
     now assigns through a temporary, in cases where such partial
     overlap is deemed possible.

  4. `libg2c' (`libf2c') no longer loses track of the file being worked
     on during a `BACKSPACE' operation.

  5. `libg2c' (`libf2c') fixes a bug whereby input to a `NAMELIST' read
     involving a repeat count, such as `K(5)=10*3', was not properly
     handled by `libf2c'.  The first item was written to `K(5)', but
     the remaining nine were written elsewhere (still within the array),
     not necessarily starting at `K(6)'.

  6. Automatic arrays now seem to be working on HP-UX systems.

  7. The `Date' intrinsic now returns the correct result on big-endian
     systems.

  8. Fix `g77' so it no longer crashes when compiling I/O statements
     using keywords that define `INTEGER' values, such as `IOSTAT=J',
     where J is other than default `INTEGER' (such as `INTEGER*2').
     Instead, it issues a diagnostic.

  9. Fix `g77' so it properly handles `DATA A/RPT*VAL/', where RPT is
     not default `INTEGER', such as `INTEGER*2', instead of producing a
     spurious diagnostic.  Also fix `DATA (A(I),I=1,N)', where `N' is
     not default `INTEGER' to work instead of crashing `g77'.

 10. The `-ax' option is now obeyed when compiling Fortran programs.
     (It is passed to the `f771' driver.)

   * The new `-fbounds-check' option causes `g77' to compile run-time
     bounds checks of array subscripts, as well as of substring start
     and end points.

   * `libg2c' now supports building as multilibbed library, which
     provides better support for systems that require options such as
     `-mieee' to work properly.

   * Source file names with the suffixes `.FOR' and `.FPP' now are
     recognized by `g77' as if they ended in `.for' and `.fpp',
     respectively.

   * The order of arguments to the *subroutine* forms of the `CTime',
     `DTime', `ETime', and `TtyNam' intrinsics has been swapped.  The
     argument serving as the returned value for the corresponding
     function forms now is the *second* argument, making these
     consistent with the other subroutine forms of `libU77' intrinsics.

   * `g77' now warns about a reference to an intrinsic that has an
     interface that is not Year 2000 (Y2K) compliant.  Also, `libg2c'
     has been changed to increase the likelihood of catching references
     to the implementations of these intrinsics using the `EXTERNAL'
     mechanism (which would avoid the new warnings).

 11. `g77' now warns about a reference to a function when the
     corresponding *subsequent* function program unit disagrees with
     the reference concerning the type of the function.

   * `-fno-emulate-complex' is now the default option.  This should
     result in improved performance of code that uses the `COMPLEX'
     data type.

   * The `-malign-double' option now reliably aligns *all*
     double-precision variables and arrays on Intel x86 targets.

 12. Even without the `-malign-double' option, `g77' reliably aligns
     local double-precision variables that are not in `EQUIVALENCE'
     areas and not `SAVE''d.

 13. `g77' now open-codes ("inlines") division of `COMPLEX' operands
     instead of generating a run-time call to the `libf2c' routines
     `c_div' or `z_div', unless the `-Os' option is specified.

   * `g77' no longer generates code to maintain `errno', a C-language
     concept, when performing operations such as the `SqRt' intrinsic.

 14. `g77' developers can temporarily use the `-fflatten-arrays' option
     to compare how the compiler handles code generation using C-like
     constructs as compared to the Fortran-like method constructs
     normally used.

 15. A substantial portion of the `g77' front end's code-generation
     component was rewritten.  It now generates code using facilities
     more robustly supported by the `gcc' back end.  One effect of this
     rewrite is that some codes no longer produce a spurious "label LAB
     used before containing binding contour" message.

   * Support for the `-fugly' option has been removed.

 16. Improve documentation and indexing, including information on Year
     2000 (Y2K) compliance, and providing more information on internals
     of the front end.

 17. Upgrade to `libf2c' as of 1999-05-10.

In 0.5.24 versus 0.5.23:
========================

   There is no `g77' version 0.5.24 at this time, or planned.  0.5.24
is the version number designated for bug fixes and, perhaps, some new
features added, to 0.5.23.  Version 0.5.23 requires `gcc' 2.8.1, as
0.5.24 was planned to require.

   Due to `EGCS' becoming `GCC' (which is now an acronym for "GNU
Compiler Collection"), and `EGCS' 1.2 becoming officially designated
`GCC' 2.95, there seems to be no need for an actual 0.5.24 release.

   To reduce the confusion already resulting from use of 0.5.24 to
designate `g77' versions within `EGCS' versions 1.0 and 1.1, as well as
in versions of `g77' documentation and notices during that period,
"mainline" `g77' version numbering resumes at 0.5.25 with `GCC' 2.95
(`EGCS' 1.2), skipping over 0.5.24 as a placeholder version number.

   To repeat, there is no `g77' 0.5.24, but there is now a 0.5.25.
Please remain calm and return to your keypunch units.

In `EGCS' 1.1.2 versus `EGCS' 1.1.1:
====================================

   * Fix the `IDate' intrinsic (VXT) (in `libg2c') so the returned year
     is in the documented, non-Y2K-compliant range of 0-99, instead of