[gcc r14-8751] libstdc++: Fix experimental/names.cc failure on AIX

[Jonathan Wakely]

https://gcc.gnu.org/g:f929293589009f82d19d6df447af6f7e7b984107

commit r14-8751-gf929293589009f82d19d6df447af6f7e7b984107
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Fri Feb 2 10:46:52 2024 +0000

    libstdc++: Fix experimental/names.cc failure on AIX
    
    This fails due to "u" being used in a system header.
    
    FAIL: experimental/names.cc  -std=gnu++17 (test for excess errors)
    Excess errors:
    /usr/include/sys/poll.h:77: error: expected unqualified-id before ';' token
    /usr/include/sys/poll.h:77: error: expected ')' before ';' token
    
    FAIL: experimental/names.cc  -std=gnu++17 (test for excess errors)
    Excess errors:
    /usr/include/sys/poll.h:102: error: expected unqualified-id before ';' token
    /usr/include/sys/poll.h:102: error: expected ')' before ';' token
    
    libstdc++-v3/ChangeLog:
    
            * testsuite/17_intro/names.cc [_AIX]: Undefine "u".

Diff:
---
 libstdc++-v3/testsuite/17_intro/names.cc | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/libstdc++-v3/testsuite/17_intro/names.cc b/libstdc++-v3/testsuite/17_intro/names.cc
index 53c5aff219d3..784da9a73522 100644
--- a/libstdc++-v3/testsuite/17_intro/names.cc
+++ b/libstdc++-v3/testsuite/17_intro/names.cc
@@ -240,6 +240,8 @@
 #undef r
 #undef x
 #undef y
+// <sys/poll.h> defines pollfd_ext::u on AIX 7.3
+#undef u
 // <sys/var.h> defines vario::v
 #undef v
 // <sys/timer.h> defines trb::func and cputime_tmr::func