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Changes made to recent versions of GNU Fortran are listed below, with the most recent version first.
The changes are generally listed in order:
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-3.3.6 version of g77, see Known Bugs In GNU Fortran.
An online, “live” version of this document (derived directly from the mainline, development version of g77 within gcc) is available at http://gcc.gnu.org/onlinedocs/g77/News.html.
The following information was last updated on 2003-05-18:
GCC 3.3 versus GCC 3.2:183239246286636764916742711372367278738473888587903892631019710726GCC 3.2 versus GCC 3.1:768183089258GCC 3.1 (formerly known as g77-0.5.27) versus GCC 3.0:94737433807395742794730475248855122539754735837610661386304 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,
and the limit is now 2 Gbyte of memory (around 530 000 000 REALs).
Note: On GNU/Linux systems one has to compile and link programs that occupy
more than 1 Gbyte statically, i.e. g77 -static ....
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.
string(1:0).
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.
GCC 3.0 versus GCC 2.95:ftruncate OS function. Thanks go to the GAMESS developers
for bringing this to our attention.
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.
TtyNam intrinsics now set Name to all spaces (at run time)
if the system has no ttyname implementation available.
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)'.
GCC 2.95 (EGCS 1.2) versus EGCS 1.1.2: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.
INTEGER(KIND=2)
(usually INTEGER*8)
subscript expressions when evaluating array references
on systems with pointers widers than INTEGER(KIND=1)
(such as Alphas).
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)'.
Date intrinsic now returns the correct result
on big-endian systems.
INTEGER values,
such as `IOSTAT=j',
where j is other than default INTEGER
(such as INTEGER*2).
Instead, it issues a diagnostic.
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.
libg2c now supports building as multilibbed library,
which provides better support for systems
that require options such as -mieee
to work properly.
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.
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).
See Year 2000 (Y2K) Problems, for more information.
COMPLEX data type.
EQUIVALENCE areas
and not SAVE'd.
COMPLEX operands
instead of generating a run-time call to
the libf2c routines c_div or z_div,
unless the -Os option is specified.
errno,
a C-language concept,
when performing operations such as the SqRt intrinsic.
libf2c as of 1999-05-10.
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.
EGCS 1.1.2 versus EGCS 1.1.1: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.
See IDate Intrinsic (VXT), for more information.
Date_and_Time intrinsic (in libg2c)
to return the milliseconds value properly
in Values(8).
LStat intrinsic (in libg2c)
to return device-ID information properly
in SArray(7).
EGCS 1.1.1 versus EGCS 1.1: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.)
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.)
Rand intrinsic on some systems.
if constructs
for the completion code to be set properly).
EGCS 1.1 versus EGCS 1.0.3: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.
This bug is not known to have existed in any
recent version of gcc.
It was introduced in an early release of egcs.
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.
ENTRY statements.
INTEGER expression.
ENTRY can be stepped through, line by line,
in gdb.
REAL argument to intrinsics
Second and CPU_Time.
tempnam, if available, to open scratch files
(as in `OPEN(STATUS='SCRATCH')')
so that the TMPDIR environment variable,
if present, is used.
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.
libf2c library from netlib they
wish to use on a case-by-case basis.
See the installation documentation for more information.
netlib they
wish to use on a case-by-case basis.
See the installation documentation for more information.
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.
install-info now used to update the directory of
Info documentation to contain an entry for g77
(during installation).
OPEN, INQUIRE, READ, and
WRITE statements,
and about truncations of various sorts of constants.
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'.
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.
EGCS 1.1 versus g77 0.5.23:DNRM2 routine.
The x87 coprocessor stack was being
mismanaged in cases involving assigned GOTO
and ASSIGN.
EQUIVALENCE and COMMON
aggregates that, due to “unnatural” ordering of members
vis-a-vis their types, require initial padding.
Previously, g77 treated these expressions as denoting special “pointer” arguments for the purposes of filewide analysis.
COMPLEX arithmetic
(especially multiplication).
Generally, this affects only local variables and arrays
having the SAVE attribute
or given initial values via DATA.
libf2c (libg2c).
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.
Date_and_Time intrinsic now is
supported.
System_Clock intrinsic allows
the optional arguments (except for the Count
argument) to be omitted.
libf2c as of 1998-06-18.
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:
__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.)
(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.)
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.
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.
CASE DEFAULT no longer crashes g77.
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.
libf2c library from netlib they
wish to use on a case-by-case basis.
See the installation documentation for more information.
netlib they
wish to use on a case-by-case basis.
See the installation documentation for more information.
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.
ENTRY statements.
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.
install-info now used to update the directory of
Info documentation to contain an entry for g77
(during installation).
OPEN, INQUIRE, READ, and
WRITE statements,
and about truncations of various sorts of constants.
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.
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.
DNRM2 routine.
The x87 coprocessor stack was being
mismanaged in cases involving assigned GOTO
and ASSIGN.
DTime intrinsic so as not to truncate
results to integer values (on some systems).
Signal intrinsic so it offers portable
support for 64-bit systems (such as Digital Alphas
running GNU/Linux).
NAMELIST on 64-bit
machines such as Alphas.
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).
CASE statement with
an omitted lower or upper bound.
CPU_Time
intrinsic.
COMPLEX arithmetic
(especially multiplication).
DOUBLE COMPLEX.
INTEGER expression.
ENTRY can be stepped through, line by line,
in gdb.
REAL argument to intrinsics
Second and CPU_Time.
Int2 and Int8.
tempnam, if available, to open scratch files
(as in `OPEN(STATUS='SCRATCH')')
so that the TMPDIR environment variable,
if present, is used.
restrict to
__restrict__, to avoid rejecting valid, existing,
C programs.
Support for restrict is now more like support
for complex.
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.)
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'.
libf2c.
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).
EGCS 1.0.2 versus EGCS 1.0.1:CASE statement with
an omitted lower or upper bound.
DOUBLE COMPLEX.
EGCS 1.0.1 versus EGCS 1.0:NAMELIST on 64-bit
machines such as Alphas.
EGCS 1.0 versus g77 0.5.21: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:
restrict keyword.
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.
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.
DTime intrinsic so as not to truncate
results to integer values (on some systems).
egcs versions of gcc.
Int2 and Int8.
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.)
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).
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).
DATA
or similar to initialize a COMPLEX variable or
array to zero.
AND, OR,
or XOR intrinsics.
COMMON
or EQUIVALENCE variable
as the target of an ASSIGN
or assigned-GOTO statement.
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.
SAVE or the -fno-automatic option
is in effect.
This avoids a compiler crash in some cases.
DOUBLE PRECISION optimally on Pentium and
Pentium Pro architectures (586 and 686 in gcc).
The default is to issue such warnings, which are new as of this version of g77.
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.
DATA statement,
and the second specification was an implied-DO list.
COMPLEX
arithmetic (especially multiplication) don't appear to
take forever to compile.
gcc-2.7.2.3.tar.gz
distribution.)
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.
CHMOD intrinsic to work with file names
that have embedded blanks, commas, and so on.
SIGNAL intrinsic so it accepts an
optional third Status argument.
IDATE() intrinsic subroutine (VXT form)
so it accepts arguments in the correct order.
Documentation fixed accordingly, and for
GMTIME() and LTIME() as well.
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.
libU77 so it is more portable.
restrict keyword in gcc
front end.
INT2 and INT8 intrinsics.
CPU_TIME intrinsic.
ALARM intrinsic.
CTIME intrinsic now accepts any INTEGER
argument, not just INTEGER(KIND=2).
libf2c build procedure to re-archive library
if previous attempt to archive was interrupted.
libf2c as of 1997-08-16.
libf2c to consistently and clearly diagnose
recursive I/O (at run time).
stderr instead of stdout.
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'.
INTEGER(KIND=0) for future use.
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.)
See Options Controlling Fortran Dialect, for information on the -ftypeless-boz option.
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.
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.
See Output Assumed To Flush, for more information.
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.
See VXT Fortran, for more information on the constructs recognized when the -fvxt option is specified.
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.
See Other Dialects, for more information.
(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.)
See Ugly Assumed-Size Arrays, for more information.
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).
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.
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.
See 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.
CONJG() and DCONJG() intrinsics now
are compiled in-line.
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.)
See Ugly Assigned Labels, for more information.
FORMAT and ENTRY statements now are allowed to
precede IMPLICIT NONE statements.
SELECT CASE on
CHARACTER type, instead of crashing, at compile time.
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).
libf2c as of 1997-02-08, and
fix up some of the build procedures.
gcc/).
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.
libf2c so that `g77 -v'
yields version information on the library.
SNGL and FLOAT intrinsics now are
specific intrinsics, instead of synonyms for the
generic intrinsic REAL.
REALPART, IMAGPART,
COMPLEX,
LONG, and SHORT.
gnu, has been added
to contain the new REALPART, IMAGPART,
and COMPLEX intrinsics.
An old group, dcp, has been removed.
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.
(Hence the menu item M for the node
Diagnostics in the top-level menu of
the Info documentation.)
Information on previous versions is archived
in gcc/gcc/f/news.texi
following the test of the DOC-OLDNEWS macro.