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This chapter describes changes to g77 that are visible
to the programmers who actually write and maintain Fortran
code they compile with g77.
Information on changes to installation procedures,
changes to the documentation, and bug fixes is
not provided here, unless it is likely to affect how
users use g77.
See section News About GNU Fortran, for information on
such changes to g77.
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 now
obsolete - 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-2.97 version of g77,
see section Known Bugs In GNU Fortran.
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-2.97 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.
The following information was last updated on 1999-07-08:
GCC 2.95 (EGCS 1.2) versus EGCS 1.1.2: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.
g77
as if they ended in `.for' and `.fpp', respectively.
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).
See section Year 2000 (Y2K) Problems, for more information.
COMPLEX data type.
g77 no longer generates code to maintain errno,
a C-language concept,
when performing operations such as the SqRt intrinsic.
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:EGCS 1.1.1 versus EGCS 1.1:EGCS 1.1 versus EGCS 1.0.3:INTEGER expression.
g77 `-g' option so procedures that
use 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.
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 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.
OPEN, INQUIRE, READ, and
WRITE statements,
and about truncations of various sorts of constants.
EGCS 1.1 versus g77 0.5.23: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.
SAVE attribute
or given initial values via DATA.
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.
Date_and_Time intrinsic now is
supported.
System_Clock intrinsic allows
the optional arguments (except for the Count
argument) to be omitted.
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,
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.)
gcc version 2.8,
and remove support for prior versions of gcc.
g77 now does all the driving,
just like gcc.
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.
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.
OPEN, INQUIRE, READ, and
WRITE statements,
and about truncations of various sorts of constants.
Signal intrinsic so it offers portable
support for 64-bit systems (such as Digital Alphas
running GNU/Linux).
INTEGER expression.
g77 `-g' option so procedures that
use 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.
gcc keyword restrict to
__restrict__, to avoid rejecting valid, existing,
C programs.
Support for restrict is now more like support
for complex.
EGCS 1.0.2 versus EGCS 1.0.1:EGCS 1.0.1 versus EGCS 1.0: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.
g77 now does all the driving,
just like gcc.
Int2 and Int8.
gcc, g77,
and other GNU compilers that incorporate the gcc
back end as modified by g77, issue
a warning about integer division by constant zero.
g77.
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.
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.
INT2 and INT8 intrinsics.
CPU_TIME intrinsic.
ALARM intrinsic.
CTIME intrinsic now accepts any INTEGER
argument, not just INTEGER(KIND=2).
g77 driver now prints version information (such as produced
by g77 -v) to stderr instead of stdout.
ratfor command, available
separately.
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 section Options Controlling Fortran Dialect,
for information on the `-ftypeless-boz' option.
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 section 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.
g77.
See section Other Dialects, 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 section 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.
g77 uses a separate memory location
to hold assigned statement labels.)
See section Ugly Assigned Labels, for more information.
FORMAT and ENTRY statements now are allowed to
precede IMPLICIT NONE statements.
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.
g77 driver and 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.
Information on previous versions is archived
in `gcc/gcc/f/news.texi'
following the test of the DOC-OLDNEWS macro.
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