From 5295cbb0a4573ea886f21d4f5e89ce7beaf60f58 Mon Sep 17 00:00:00 2001 From: Peter Eisentraut Date: Fri, 13 Mar 2026 11:20:31 +0100 Subject: [PATCH] Hardcode override of typeof_unqual for clang-for-bitcode The fundamental problem is that when we call clang to generate bitcode, we might be using configure results from a different compiler, which might not be fully compatible with the clang we are using. In practice, clang supports most things other compilers support, so this has apparently not been a problem in practice. But commits 4cfce4e62c8, 0af05b5dbb4, and 59292f7aac7 have been struggling to make typeof_unqual work in this situation. Clang added support in version 19, GCC in version 14, so if you are using, say, GCC 14 and Clang 16, the compilation with the latter will fail. Again, in practice, this might be unlikely, because GCC 14 and Clang 19 were released within a few months of each other, and so Linux distributions are likely to have suitable combinations. But buildfarm member "taipan" does not (gcc 15, clang 16), so I'll try to fix it. The fully correct solution would be to run a separate set of configure tests for that clang-for-bitcode, but that would be very difficult to implement, and probably of limited use in practice. So the workaround here is that we hardcodedly override the configure result under clang based on the version number. As long as we only have a few of these cases, this should be manageable. Discussion: https://www.postgresql.org/message-id/flat/92f9750f-c7f6-42d8-9a4a-85a3cbe808f3%40eisentraut.org --- src/include/c.h | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/src/include/c.h b/src/include/c.h index 2aab74d8b0e..2e789b00594 100644 --- a/src/include/c.h +++ b/src/include/c.h @@ -432,6 +432,21 @@ extern "C++" #define unlikely(x) ((x) != 0) #endif +/* + * When we call clang to generate bitcode, we might be using configure results + * from a different compiler, which might not be fully compatible with the + * clang we are using. The fully correct solution would be to run a separate + * set of configure tests for that clang-for-bitcode, but that could be very + * difficult to implement, and in practice clang supports most things other + * compilers support. So this section just contains some hardcoded ugliness + * to override some configure results where it is necessary. + */ +#if defined(__clang__) +#if __clang_major__ < 19 +#undef HAVE_TYPEOF_UNQUAL +#endif +#endif /* __clang__ */ + /* * Provide typeof in C++ for C++ compilers that don't support typeof natively. * It might be spelled __typeof__ instead of typeof, in which case -- 2.53.0