This is g77.info, produced by makeinfo version 4.2 from g77.texi.

INFO-DIR-SECTION Programming
START-INFO-DIR-ENTRY
* g77: (g77).                  The GNU Fortran compiler.
END-INFO-DIR-ENTRY
   This file documents the use and the internals of the GNU Fortran
(`g77') compiler.  It corresponds to the GCC-3.1 version of `g77'.

   Published by the Free Software Foundation 59 Temple Place - Suite 330
Boston, MA 02111-1307 USA

   Copyright (C) 1995,1996,1997,1998,1999,2000,2001,2002 Free Software
Foundation, Inc.

   Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.1 or
any later version published by the Free Software Foundation; with the
Invariant Sections being "GNU General Public License" and "Funding Free
Software", the Front-Cover texts being (a) (see below), and with the
Back-Cover Texts being (b) (see below).  A copy of the license is
included in the section entitled "GNU Free Documentation License".

   (a) The FSF's Front-Cover Text is:

   A GNU Manual

   (b) The FSF's Back-Cover Text is:

   You have freedom to copy and modify this GNU Manual, like GNU
software.  Copies published by the Free Software Foundation raise
funds for GNU development.

   Contributed by James Craig Burley (<craig@jcb-sc.com>).  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>).


File: g77.info,  Node: News,  Next: Changes,  Prev: Invoking G77,  Up: Top

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.  Note that all such variants are
obsolete _as of July 1999_ - the information is retained here only for
its historical value.

   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.

   For information on bugs in the GCC-3.1 version of `g77', see *Note
Known Bugs In GNU Fortran: Known Bugs.

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

   The following information was last updated on 2002-04-13:

In `GCC' 3.1 (formerly known as g77-0.5.27) versus `GCC' 3.0:
=============================================================

   * Problem Reports fixed (in chronological order of submission):
    `947'
          Data statement initialization with subscript of kind INTEGER*2

    `3743'
          Reference to intrinsic `ISHFT' invalid

    `3807'
          Function BESJN(integer,double) problems

    `3957'
          g77 -pipe -xf77-cpp-input sends output to stdout

    `4279'
          g77 -h" gives bogus output

    `4730'
          ICE on valid input using CALL EXIT(%VAL(...))

    `4752'
          g77 -v -c -xf77-version /dev/null -xnone causes ice

    `4885'
          BACKSPACE example that doesn't work as of gcc/g77-3.0.x

    `5122'
          g77 rejects accepted use of INTEGER*2 as type of DATA
          statement loop index

    `5397'
          ICE on compiling source with 540 000 000 REAL array

    `5473'
          ICE on BESJN(integer*8,real)

    `5837'
          bug in loop unrolling

   * `g77' now has its man page generated from the texinfo
     documentation, to guarantee that it remains up to date.

   * `g77' used to reject the following program on 32-bit targets:
          PROGRAM PROG
          DIMENSION A(140 000 000)
          END
     with the message:
          prog.f: In program `prog':
          prog.f:2:
                   DIMENSION A(140 000 000)
                             ^
          Array `a' at (^) is too large to handle
     because 140 000 000 reals is larger than the largest bit-extent
     that can be expressed in 32 bits.  However, bit-sizes never play a
     role after offsets have been converted to byte addresses.
     Therefore this check has been removed.  Note: On GNU/Linux systems
     one has to compile programs that occupy more than 1 Gbyte
     statically, i.e. `g77 -static ...'.

   * Based on work done by Juergen Pfeifer (<juergen.pfeifer@gmx.net>)
     libf2c is now a shared library.  One can still link in all objects
     with the program by specifying the `-static' option.

   * Robert Anderson (<rwa@alumni.princeton.edu>) thought up a two line
     change that enables g77 to compile such code as:
          SUBROUTINE SUB(A, N)
          DIMENSION N(2)
          DIMENSION A(N(1),N(2))
          A(1,1) = 1.
          END
     Note the use of array elements in the bounds of the adjustable
     array A.

   * George Helffrich (<george@geo.titech.ac.jp>) implemented a change
     in substring index checking (when specifying `-fbounds-check')
     that permits the use of zero length substrings of the form
     `string(1:0)'.

   * Based on code developed by Pedro Vazquez
     (<vazquez@penelope.iqm.unicamp.br>), the `libf2c' library is now
     able to read and write files larger than 2 Gbyte on 32-bit target
     machines, if the operating system supports this.

In 0.5.26, `GCC' 3.0 versus `GCC' 2.95:
=======================================

   * When a REWIND was issued after a WRITE statement on an unformatted
     file, the implicit truncation was performed by copying the
     truncated file to /tmp and copying the result back.  This has been
     fixed by using the `ftruncate' OS function.  Thanks go to the
     GAMESS developers for bringing this to our attention.

   * Using options `-g', `-ggdb' or `-gdwarf[-2]' (where appropriate
     for your target) now also enables debugging information for COMMON
     BLOCK and EQUIVALENCE items to be emitted.  Thanks go to Andrew
     Vaught (<andy@xena.eas.asu.edu>) and George Helffrich
     (<george@geology.bristol.ac.uk>) for fixing this longstanding
     problem.

   * It is not necessary anymore to use the option `-femulate-complex'
     to compile Fortran code using COMPLEX arithmetic, even on 64-bit
     machines (like the Alpha).  This will improve code generation.

   * INTRINSIC arithmetic functions are now treated as routines that do
     not depend on anything but their argument(s).  This enables
     further instruction scheduling, because it is known that they
     cannot read or modify arbitrary locations.

   * Upgrade to `libf2c' as of 2000-12-05.

     This fixes a bug where a namelist containing initialization of
     LOGICAL items and a variable starting with T or F would be read
     incorrectly.

   * The `TtyNam' intrinsics now set NAME to all spaces (at run time)
     if the system has no `ttyname' implementation available.

   * Upgrade to `libf2c' as of 1999-06-28.

     This 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)'.

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

   * `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.

   * `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).

   * `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.

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

   * `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)'.

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

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

   * 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.

   * 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'.

   * 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).

     *Note Year 2000 (Y2K) Problems::, for more information.

   * `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.

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

   * `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.

   * `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.

   * 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.

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

   * 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
     being returned as 100 in the year 2000.

     *Note IDate Intrinsic (VXT)::, for more information.

   * 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 `EGCS' 1.1.1 versus `EGCS' 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 `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' hierarchy, 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' hierarchy, 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
     hierarchy, `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 hierarchy, `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 `EGCS' 1.1 versus `g77' 0.5.23:
==================================

   * 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'.

   * `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.

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

   * `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.

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

   * 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'.

   * 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' hierarchy, 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' hierarchy, 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
     hierarchy, `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 hierarchy, `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 `g77' 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).

   * Some Fortran code, miscompiled by `g77' built on `gcc' version
     2.8.1 on m68k-next-nextstep3 configurations when using the `-O2'
     option, is now compiled correctly.  It is believed that a C
     function known to miscompile on that configuration when using the
     `-O2 -funroll-loops' options also is now compiled correctly.

   * 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 occurred 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(KIND=1)' constants.  Specify `-ftypeless-boz' to cause
     such constants to be interpreted as typeless.

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

     *Note Options Controlling Fortran Dialect: Fortran Dialect Options,
     for information on the `-ftypeless-boz' option.

   * 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'.

     *Note Output Assumed To Flush::, for more information.

   * 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.

     *Note VXT Fortran::, for more information on the constructs
     recognized when the `-fvxt' option is specified.

   * 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'.

     *Note Other Dialects::, for more information.

   * 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.

     *Note Ugly Assumed-Size Arrays::, for more information.

   * 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(KIND=0)' type,
     as defined by the GNU Fortran language.

     This type is wide enough (holds the same number of bits) as the
     character-pointer type on the machine.

     On most machines, this won't make a difference, whereas, on Alphas
     and other systems with 64-bit pointers, the `INTEGER(KIND=0)' type
     is equivalent to `INTEGER(KIND=2)' (often referred to as
     `INTEGER*8') instead of the more common `INTEGER(KIND=1)' (often
     referred to as `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.

     *Note Aliasing Assumed To Work::, for detailed information on why
     the new defaults might result in some programs no longer working
     the way they did when compiled by previous versions of `g77'.

   * 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.)

     *Note Ugly Assigned Labels::, for more information.

   * `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(KIND=2)' (often referred to as
     `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(KIND=2)' 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 previous versions:
=====================

   Information on previous versions is archived in `gcc/gcc/f/news.texi'
following the test of the `DOC-OLDNEWS' macro.

