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[Bug libc/12469] New: Race condition in configure.in check for necessary ranlib
- From: "bruce.dubbs at gmail dot com" <sourceware-bugzilla at sourceware dot org>
- To: glibc-bugs at sources dot redhat dot com
- Date: Sun, 6 Feb 2011 21:22:54 +0000
- Subject: [Bug libc/12469] New: Race condition in configure.in check for necessary ranlib
- Auto-submitted: auto-generated
http://sourceware.org/bugzilla/show_bug.cgi?id=12469
Summary: Race condition in configure.in check for necessary
ranlib
Product: glibc
Version: 2.13
Status: NEW
Severity: minor
Priority: P2
Component: libc
AssignedTo: drepper.fsp@gmail.com
ReportedBy: bruce.dubbs@gmail.com
In configure.in, starting at line 1098, the code to check if ranlib is
necessary is:
# check if ranlib is necessary
AC_CACHE_CHECK(whether ranlib is necessary, libc_cv_ranlib_necessary, [dnl
cat > conftest.c <<EOF
int a;
char b;
void c(void) {}
EOF
$CC $CFLAGS $CPPFLAGS -c conftest.c
$AR cr conftest.a conftest.o
cp conftest.a conftest2.a
$RANLIB conftest.a
if cmp -s conftest.a conftest2.a; then
libc_cv_ranlib_necessary=no
else
libc_cv_ranlib_necessary=yes
fi
Under some infrequent timing conditions, the test can sometimes return yes when
it shouldn't. This is because ranlib adds a timestamp from byte position 24 to
33 that can differ between the creation of conftest.a and it's modification two
lines later.
I suggest changing the comparison test to:
if cmp -s -i34 conftest.a conftest2.a; then
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