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Import latest m4/m4.m4.

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* m4/m4.m4: Copy from autoconf 2.64.
* configure.ac (M4_GNU_OPTION): New define.
* src/output.c (output_skeleton): Use it to resolve FIXME.
* NEWS: Mention this.

Signed-off-by: Eric Blake <ebb9@byu.net>
This commit is contained in:
Eric Blake
2009-08-20 08:24:46 -06:00
parent b1a4261e6d
commit b9ad39c1fb
5 changed files with 65 additions and 32 deletions
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33
src/output.c
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@@ -473,7 +473,7 @@ output_skeleton (void)
FILE *in;
FILE *out;
int filter_fd[2];
char const *argv[9];
char const *argv[10];
pid_t pid;
/* Compute the names of the package data dir and skeleton files. */
@@ -524,6 +524,19 @@ output_skeleton (void)
{
int i = 0;
argv[i++] = m4;
/* When POSIXLY_CORRECT is set, GNU M4 1.6 and later disable GNU
extensions, which Bison's skeletons depend on. With older M4,
it has no effect. M4 1.4.12 added a -g/--gnu command-line
option to make it explicit that a program wants GNU M4
extensions even when POSIXLY_CORRECT is set.
See the thread starting at
<http://lists.gnu.org/archive/html/bug-bison/2008-07/msg00000.html>
for details. */
if (*M4_GNU_OPTION)
argv[i++] = M4_GNU_OPTION;
argv[i++] = "-I";
argv[i++] = pkgdatadir;
if (trace_flag & trace_m4)
@@ -534,25 +547,7 @@ output_skeleton (void)
argv[i++] = full_skeleton;
argv[i++] = NULL;
}
/* When POSIXLY_CORRECT is set, some future versions of GNU M4 (most likely
2.0) may drop some of the GNU extensions that Bison's skeletons depend
upon. So that the next release of Bison is forward compatible with those
future versions of GNU M4, we unset POSIXLY_CORRECT here.
FIXME: A user might set POSIXLY_CORRECT to affect processes run from
macros like m4_syscmd in a custom skeleton. For now, Bison makes no
promises about the behavior of custom skeletons, so this scenario is not a
concern. However, we eventually want to eliminate this shortcoming. The
next release of GNU M4 (1.4.12 or 1.6) will accept the -g command-line
option as a no-op, and later releases will accept it to indicate that
POSIXLY_CORRECT should be ignored. Once the GNU M4 versions that accept
-g are pervasive, Bison should use -g instead of unsetting
POSIXLY_CORRECT.
See the thread starting at
<http://lists.gnu.org/archive/html/bug-bison/2008-07/msg00000.html>
for details. */
unsetenv ("POSIXLY_CORRECT");
init_subpipe ();
pid = create_subpipe (argv, filter_fd);
free (full_m4sugar);