stdalign tests: Skip test with AIX xlclang

[Bruno Haible]

With the 'xlclang' compiler on AIX, I see no way to make 'alignas' or
'_Alignas' work. The unit test keeps failing:

../../gltests/test-stdalign.c:93: assertion '(uintptr_t) &(static_char_alignas) 
% TEST_ALIGNMENT == 0' failed

We can mark this test as SKIP, since it's an expected failure now.


2020-08-20  Bruno Haible  <br...@clisp.org>

        stdalign tests: Skip test with AIX xlclang.
        * tests/test-stdalign.c (main): Skip alignas tests with AIX xlclang.

diff --git a/tests/test-stdalign.c b/tests/test-stdalign.c
index 65e5c6a..6451168 100644
--- a/tests/test-stdalign.c
+++ b/tests/test-stdalign.c
@@ -89,6 +89,11 @@ main ()
      https://lists.gnu.org/r/bug-gnulib/2017-03/msg00078.html  */
   fputs ("Skipping test: known HP-UX Itanium cc compiler bug\n", stderr);
   return 77;
+#elif defined __clang__ && defined __ibmxl__
+  /* Avoid a test failure with IBM xlc 16.1.  It ignores alignas (8),
+     _Alignas (8), and __attribute__ ((__aligned__ (8))).  */
+  fputs ("Skipping test: known AIX XL C compiler deficiency\n", stderr);
+  return 77;
 #else
   CHECK_ALIGNED (static_char_alignas);
   CHECK_ALIGNED (static_char_Alignas);