[gcc r12-8609] libstdc++: Do not include <cxxabi.h> in <stacktrace>

[Jonathan Wakely <redi@gcc.gnu.org>]

https://gcc.gnu.org/g:98ce66a48fb01475e011757464c49a3b284ae5da

commit r12-8609-g98ce66a48fb01475e011757464c49a3b284ae5da
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Fri May 6 13:23:45 2022 +0100

    libstdc++: Do not include <cxxabi.h> in <stacktrace>
    
    This avoids polluting the global namespace with the "abi" namespace
    alias.
    
    libstdc++-v3/ChangeLog:
    
            * include/std/stacktrace: Do not include <cxxabi.h>.
            (__cxa_demangle): Declare.
    
    (cherry picked from commit e112e37f2920bcc9185e53b754d9145aac912c72)

Diff:
---
 libstdc++-v3/include/std/stacktrace | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/libstdc++-v3/include/std/stacktrace b/libstdc++-v3/include/std/stacktrace
index 98ce9231150..8e6c79a2f4f 100644
--- a/libstdc++-v3/include/std/stacktrace
+++ b/libstdc++-v3/include/std/stacktrace
@@ -38,7 +38,6 @@
 #include <bits/stl_iterator.h>
 #include <bits/stl_uninitialized.h>
 #include <ext/numeric_traits.h>
-#include <cxxabi.h>
 
 struct __glibcxx_backtrace_state;
 struct __glibcxx_backtrace_simple_data;
@@ -70,6 +69,13 @@ __glibcxx_backtrace_syminfo(__glibcxx_backtrace_state*, uintptr_t addr,
 			    void*);
 }
 
+namespace __cxxabiv1
+{
+  extern "C" char*
+  __cxa_demangle(const char* __mangled_name, char* __output_buffer,
+		 size_t* __length, int* __status);
+}
+
 namespace std _GLIBCXX_VISIBILITY(default)
 {
 _GLIBCXX_BEGIN_NAMESPACE_VERSION