[PATCH v2] tests: allow tests to append tunables

[Yury Khrustalev]

On Mon, Apr 13, 2026 at 03:26:18PM +0100, Yury Khrustalev wrote:
> Many tests use Glibc tunables. The tunable values are provided via
> the GLIBC_TUNABLES env variable. Tests set it in makefiles using
> 
>   tst-foo-ENV = GLIBC_TUNABLES=tunable=value
> 
> This overwrites environment for this test, so if another env var is
> set elsewhere, one of these changes would be lost. The correct way
> should be to append to test's environment:
> 
>   tst-foo-ENV += GLIBC_TUNABLES=tunable=value
> 
> However, if two or more tunables need to be set for the same test,
> the 'tunable=value' part should be appended to previously defined
> GLIBC_TUNABLES env variable.
> 
> This commit adds 'tunable-add' that can be used to correctly append
> another tunable to a test's environment. We also change tests in the
> malloc and misc folder.

If it is better to use something like as suggested in [1]

  tst-foo-TUNABLES

instead of modifying the whole environment of the test via

  tst-foo-ENV += GLIBC_TUNABLES=tunable=value

or

  $(eval $(call tunable-add, ...))

I can certainly look into this and send another patch. This might be a
better way of doing it.

Thanks,
Yury

----
[1]: https://inbox.sourceware.org/libc-alpha/53ce1324-63a9-488b-955b-99700e4fdcd6@linaro.org