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Fix timing bug on high-speed builds

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Problem reported by Bogdan via Jacob Bachmeyer in:
https://lists.gnu.org/r/autoconf/2023-04/msg00002.html
* bin/autom4te.in: If a file timestamp equals a dependency’s
timestamp, consider the file to be out of date.  Although this may
result in extra work, it fixes some rare timing bugs.
This commit is contained in:
Paul Eggert 2023-04-01 16:44:03 -07:00
parent 05e295b60c
commit 713d9822bb
1 changed files with 5 additions and 7 deletions
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12
bin/autom4te.in
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@ -910,10 +910,8 @@ sub up_to_date ($)
return 0
if ! -f $tfile || ! -f $ofile;
# The youngest of the cache files must be older than the oldest of
# The younger of the cache files must be older than the oldest of
# the dependencies.
# FIXME: These timestamps have only 1-second resolution.
# Time::HiRes fixes this, but assumes Perl 5.8 or later.
my $tmtime = mtime ($tfile);
my $omtime = mtime ($ofile);
my ($file, $mtime) = ($tmtime < $omtime
@ -926,7 +924,7 @@ sub up_to_date ($)
# We depend at least upon the arguments.
foreach my $dep (@ARGV)
{
if ($mtime < mtime ($dep))
if ($mtime <= mtime ($dep))
{
verb "up_to_date ($file): outdated: $dep";
return 0;
@ -949,7 +947,7 @@ sub up_to_date ($)
# timestamp of that missing file was newer).
return 0
if ! $dep;
if ($mtime < mtime ($dep))
if ($mtime <= mtime ($dep))
{
verb "up_to_date ($file): outdated: $dep";
return 0;
@ -1038,7 +1036,7 @@ $icache_file = new Autom4te::XFile $icache, O_RDWR|O_CREAT;
$icache_file->lock (LOCK_EX)
if ($flock_implemented eq "yes");
# Read the cache index if available and older than autom4te itself.
# Read the cache index if available and younger than autom4te itself.
# If autom4te is younger, then some structures such as C4che might
# have changed, which would corrupt its processing.
Autom4te::C4che->load ($icache_file)
@ -1105,7 +1103,7 @@ else
# Actual M4 expansion, if the user wants it, or if $output is old
# (STDOUT is pretty old).
handle_output ($req, $output)
if $force || mtime ($output) < mtime ($ocache . $req->id);
if $force || mtime ($output) <= mtime ($ocache . $req->id);
}
# If we ran up to here, the cache is valid.