Re: [PATCH v3] test-lib.sh: Use GLIBC_TUNABLES instead of MALLOC_CHECK_ on glibc >= 2.34

[Phillip Wood <phillip.wood123@gmail.com>]

On 04/03/2022 13:37, Elia Pinto wrote:
> In glibc >= 2.34 MALLOC_CHECK_ and MALLOC_PERTURB_ environment
> variables have been replaced by GLIBC_TUNABLES.  Also the new
> glibc requires that you preload a library called libc_malloc_debug.so
> to get these features.
> 
> Using the ordinary glibc system variable detect if this is glibc >= 2.34 and
> use GLIBC_TUNABLES and the new library.
> 
> This patch was inspired by a Richard W.M. Jones ndbkit patch
> 
> Helped-by: Junio C Hamano <gitster@pobox.com>
> Signed-off-by: Elia Pinto <gitter.spiros@gmail.com>
> ---
> This is the third version of the patch.
> 
> Compared to the second version[1], the code is further simplified,
> eliminating a case statement and modifying a string statement.
> 
> [1] https://www.spinics.net/lists/git/msg433917.html
> 
>   t/test-lib.sh | 16 ++++++++++++++++
>   1 file changed, 16 insertions(+)
> 
> diff --git a/t/test-lib.sh b/t/test-lib.sh
> index 9af5fb7674..4d10646015 100644
> --- a/t/test-lib.sh
> +++ b/t/test-lib.sh
> @@ -550,9 +550,25 @@ else
>   	setup_malloc_check () {
>   		MALLOC_CHECK_=3	MALLOC_PERTURB_=165
>   		export MALLOC_CHECK_ MALLOC_PERTURB_
> +		if _GLIBC_VERSION=$(getconf GNU_LIBC_VERSION 2>/dev/null) &&
> +		_GLIBC_VERSION=${_GLIBC_VERSION#"glibc "} &&
> +		expr 2.34 \<= "$_GLIBC_VERSION" >/dev/null
> +		then
> +			g=
> +			LD_PRELOAD="libc_malloc_debug.so.0"

When compiling with "SANITIZE = address,leak" this use of LD_PRELOAD 
makes the tests fail with

==9750==ASan runtime does not come first in initial library list; you 
should either link runtime to your application or manually preload it 
with LD_PRELOAD.

because libc_malloc_debug.so is being loaded before libasan.so. If I set 
TEST_NO_MALLOC_CHECK=1 when I run the tests then ASAN does not complain 
but it would be nicer if I did not have to do that. I'm confused as to 
why the CI leak tests are running fine - am I missing something with my 
setup?

Best Wishes

Phillip