[PATCH] test-lib: check malloc debug LD_PRELOAD before using
- From
Jeff King <peff@peff.net>
- Date
- Nov 11, 2024, 07:01 UTC
- Message-ID
- <20241111070134.GA675125@coredump.intra.peff.net>
- In-Reply-To
- <xmqq7c9aihvx.fsf@gitster.g>
On Mon, Nov 11, 2024 at 12:11:46PM +0900, Junio C Hamano wrote:
Show 18 quoted lines
> Jeff King <peff@peff.net> writes: > > > I don't offhand know of a good portable way to ask the system about > > available libraries. But I guess just doing something like: > > > > err=$(LD_PRELOAD=libc_malloc.so.0 git version 2>&1 >/dev/null) > > if test -z "$err" > > then > > ...seemed to work... > > fi > > > > would do it? > > I do not necessarily view it as "asking the system about available > libraries"; we are checking if we can sensibly run things with this > set to LD_PRELOAD. And presumably the answer was "no" in the > original report, so it is a very direct way to ensure that we are > setting it to a sensible value. I like it.
Yeah, I agree that is a better way to think about it; it is more directly asking what we want to know. So here it is as an actual patch.
> The above did not work for me until I did "s/malloc/&_debug/" on the > command line.
Oops, yes. I should have said "not tested". ;) On the other hand, writing the wrong name is an easy way to test the failure mode. I pulled it out into a variable in the patch below so we only have to write it once.
I tested before and after with a typo'd version of the library name and it seems to work. But it would be great to get confirmation from Usman that this fixes the problem.
-- >8 -- Subject: [PATCH] test-lib: check malloc debug LD_PRELOAD before using
This fixes test failures across the suite on glibc platforms that don't have libc_malloc_debug.so.0.
We added support for glibc's malloc checking routines long ago in a731fa916e (Add MALLOC_CHECK_ and MALLOC_PERTURB_ libc env to the test suite for detecting heap corruption, 2012-09-14). Back then we didn't need to do any checks to see if the platform supported it. We were just setting some environment variables which would either enable it or not.
That changed in 131b94a10a (test-lib.sh: Use GLIBC_TUNABLES instead of MALLOC_CHECK_ on glibc >= 2.34, 2022-03-04). Now that glibc split this out into libc_malloc_debug.so, we have to add it to LD_PRELOAD. We only do that when we detect glibc, but it's possible to have glibc but not the malloc debug library. In that case LD_PRELOAD will complain to stderr, and tests which check for an empty stderr will fail.
You can work around this by setting TEST_NO_MALLOC_CHECK, which disables the feature entirely. But it's not obvious to know you need to do that. Instead, since this malloc checking is best-effort anyway, let's just automatically disable it when the LD_PRELOAD appears not to work. We can check it by running something simple that should work (and produce nothing on stderr) like "git version".
Signed-off-by: Jeff King <peff@peff.net> --- t/test-lib.sh | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/t/test-lib.sh b/t/test-lib.sh index a278181a05..4fe757fe9a 100644 --- a/t/test-lib.sh +++ b/t/test-lib.sh @@ -593,9 +593,12 @@ then } else _USE_GLIBC_TUNABLES= + _USE_GLIBC_PRELOAD=libc_malloc_debug.so.0 if _GLIBC_VERSION=$(getconf GNU_LIBC_VERSION 2>/dev/null) && _GLIBC_VERSION=${_GLIBC_VERSION#"glibc "} && - expr 2.34 \<= "$_GLIBC_VERSION" >/dev/null + expr 2.34 \<= "$_GLIBC_VERSION" >/dev/null && + stderr=$(LD_PRELOAD=$_USE_GLIBC_PRELOAD git version 2>&1 >/dev/null) && + test -z "$stderr" then _USE_GLIBC_TUNABLES=YesPlease fi @@ -607,7 +610,7 @@ else if test -n "$_USE_GLIBC_TUNABLES" then g= - LD_PRELOAD="libc_malloc_debug.so.0" + LD_PRELOAD=$_USE_GLIBC_PRELOAD for t in \ glibc.malloc.check=1 \ glibc.malloc.perturb=165
-- 2.47.0.495.g1253739cc1