[gcc r15-4214] libstdc++: Workaround glibc headers on ia64-linux

[Jonathan Wakely via Libstdc++-cvs]

https://gcc.gnu.org/g:c0bc9a153ae6ab649e2fcc3af53ebcd37df0a871

commit r15-4214-gc0bc9a153ae6ab649e2fcc3af53ebcd37df0a871
Author: Frank Scheiner <frank.schei...@web.de>
Date:   Tue Oct 8 19:48:09 2024 +0100

    libstdc++: Workaround glibc headers on ia64-linux
    
    We see:
    
    ```
    FAIL: 17_intro/names.cc  -std=gnu++17 (test for excess errors)
    FAIL: 17_intro/names_pstl.cc  -std=gnu++17 (test for excess errors)
    FAIL: experimental/names.cc  -std=gnu++17 (test for excess errors)
    ```
    
    ...on ia64-linux.
    
    This is due to:
    
    * /usr/include/bits/sigcontext.h:32-38:
    ```
    32 struct __ia64_fpreg
    33   {
    34     union
    35       {
    36         unsigned long bits[2];
    37       } u;
    38   } __attribute__ ((__aligned__ (16)));
    ```
    
    * /usr/include/sys/ucontext.h:39-45:
    ```
      39 struct __ia64_fpreg_mcontext
      40   {
      41     union
      42       {
      43         unsigned long __ctx(bits)[2];
      44       } __ctx(u);
      45   } __attribute__ ((__aligned__ (16)));
    ```
    
    ...from glibc 2.39 (w/ia64 support re-added). See the discussion
    starting on [1].
    
    [1]: https://gcc.gnu.org/pipermail/gcc-patches/2024-June/654487.html
    
    Signed-off-by: Frank Scheiner <frank.schei...@web.de>
    
    libstdc++-v3/ChangeLog:
    
            * testsuite/17_intro/names.cc [__linux__ && __ia64__]: Undefine
            'u' as used in glibc headers.

Diff:
---
 libstdc++-v3/testsuite/17_intro/names.cc | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/libstdc++-v3/testsuite/17_intro/names.cc 
b/libstdc++-v3/testsuite/17_intro/names.cc
index 6b9a3639aad4..bea2d19ecba0 100644
--- a/libstdc++-v3/testsuite/17_intro/names.cc
+++ b/libstdc++-v3/testsuite/17_intro/names.cc
@@ -282,6 +282,12 @@
 #undef y
 #endif
 
+#if defined (__linux__) && defined (__ia64__)
+// <bits/sigcontext.h> defines __ia64_fpreg::u
+// <sys/ucontext.h> defines __ia64_fpreg_mcontext::u
+#undef u
+#endif
+
 #if defined (__linux__) || defined (__gnu_hurd__)
 #if __has_include(<features.h>)
 #include <features.h>