Elia Pinto <gitter.spiros@xxxxxxxxx> writes:
> Recent versions of Linux libc (later than 5.4.23) and glibc (2.x)
> include a malloc() implementation which is tunable via environment
> variables. When MALLOC_CHECK_ is set, a special (less efficient)
> implementation is used which is designed to be tolerant against
> simple errors, such as double calls of free() with the same argument,
> or overruns of a single byte (off-by-one bugs). When MALLOC_CHECK_
> is set to 3, a diagnostic message is printed on stderr
> and the program is aborted.
> ...
> Signed-off-by: Elia Pinto <gitter.spiros@xxxxxxxxx>
> ---
> This the third reroll of the original patch.
Well written. I have one suggestion and a question, though.
> t/test-lib.sh | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/t/test-lib.sh b/t/test-lib.sh
> index 78c4286..f34b861 100644
> --- a/t/test-lib.sh
> +++ b/t/test-lib.sh
> @@ -93,6 +93,15 @@ export GIT_AUTHOR_EMAIL GIT_AUTHOR_NAME
> export GIT_COMMITTER_EMAIL GIT_COMMITTER_NAME
> export EDITOR
>
> +# Add libc MALLOC and MALLOC_PERTURB test
> +# only if we are not executing the test with valgrind
> +expr "$GIT_TEST_OPTS" : ".*\(--valgrind\)" >/dev/null || {
I would write this like
if ! expr " $GIT_TEST_OPTS " : ".* --valgrind " >/dev/null
then
...
fi
> + MALLOC_CHECK_=3
> + export MALLOC_CHECK_
> + MALLOC_PERTURB_="$( expr \( $$ % 255 \) + 1)"
How was this expression chosen? The only effect I can think of to
use a randomly picked value here is to make it impossible to make
the test repeatable and reproducible, so you must have had some
benefit that outweighs the downside, but I cannot think of any.
Wouldn't MALLOC_PERTURB_=165 (i.e. 0xA5, half of the bits in the
byte is set, including the MSB, and is an odd number) be equally a
good choice without repeatability downside, for example?
Also, doesn't the above give 256 sometimes, which would not fit in a
byte?
> + export MALLOC_PERTURB_
> +}
> +
> # Protect ourselves from common misconfiguration to export
> # CDPATH into the environment
> unset CDPATH
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