[PATCH] Clear CXX and TEST_CXX if TEST_CXX link test fails

[Sam James]

"H.J. Lu" <hjl.tools@gmail.com> writes:

> On Thu, Dec 12, 2024 at 1:16 AM Joseph Myers <josmyers@redhat.com> wrote:
>>
>> This breaks the case where the $CXX compiler doesn't work.  This can be
>> seen with the m68k-linux-gnu-coldfire regressions in
>> <https://sourceware.org/pipermail/libc-testresults/2024q4/013238.html>,
>> where the "whether $CXX can link programs" test fails because of libstdc++
>> referencing hidden symbols in libgcc.a.
>>
>> In the case where CXX is set to empty because the link test failed
>>
>> AS_IF([test $libc_cv_cxx_link_ok != yes], [CXX=])
>>
>> much the same should apply to TEST_CXX if it was defaulted from CXX, so
>> that Makefile conditionals ifeq (,$(CXX)) and ifneq (,$(CXX)) work
>> correctly in such a case.
>>
>
> Here is the patch.  Tested for m68k-linux-gnu-coldfire build and native
> build on x86-64.
>
> Since the C++ compiler is only for testing, if TEST_CXX link test fails,
> clear both CXX and TEST_CXX so that the C++ compiler isn't used for glibc
> build nor test.
>
> H.J.
>
> [2. application/x-patch; 0001-Clear-CXX-and-TEST_CXX-if-TEST_CXX-link-test-fails.patch]...

LGTM with s/==/=/. I would prefer it if we moved more to AS_IF but
that's a different issue to be done en-masse.