Merge branch 'ep/test-malloc-check-with-glibc-2.34'

The method to trigger malloc check used in our tests no longer work
with newer versions of glibc.

* ep/test-malloc-check-with-glibc-2.34:
  test-lib: declare local variables as local
  test-lib.sh: Use GLIBC_TUNABLES instead of MALLOC_CHECK_ on glibc >= 2.34

Author: gitster

t/test-lib.sh

@@ -548,11 +548,29 @@ then
 	}
 else
 	setup_malloc_check () {
+		local g
+		local t
 		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 \<= "$_GLIBC_VERSION" >/dev/null
+		then
+			g=
+			LD_PRELOAD="libc_malloc_debug.so.0"
+			for t in \
+				glibc.malloc.check=1 \
+				glibc.malloc.perturb=165
+			do
+				g="${g#:}:$t"
+			done
+			GLIBC_TUNABLES=$g
+			export LD_PRELOAD GLIBC_TUNABLES
+		fi
 	}
 	teardown_malloc_check () {
 		unset MALLOC_CHECK_ MALLOC_PERTURB_
+		unset LD_PRELOAD GLIBC_TUNABLES
 	}
 fi