Debug Mode ENH 3/4: Add backtrace

[François Dumont <frs dot dumont at gmail dot com>]

Hi

    Here is the patch to add backtrace info to debug assertion failure 
output.

Example:

/home/fdt/dev/gcc/build/x86_64-pc-linux-gnu/libstdc++-v3/include/debug/vector:188:
In function:
    std::__debug::vector<_Tp, _Allocator>::vector(_InputIterator,
    _InputIterator, const _Allocator&) [with _InputIterator =
std::reverse_iterator<__gnu_debug::_Safe_tagged_iterator<__gnu_cxx::__normal_iterator<int*, 

    std::vector<int> >, std::__debug::vector<int>,
    std::random_access_iterator_tag> >; <template-parameter-2-2> = 
void; _Tp
    = int; _Allocator = std::allocator<int>]

Backtrace:
    ./debug_neg.exe() [0x4020c1]
    ./debug_neg.exe() [0x400e59]
    /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf0) 
[0x7f13fc56e830]
    ./debug_neg.exe() [0x400eb9]

I tried to use add2line on the output address and it worked fine.

Tested under Linux x86_64.

I'll commit tomorrow if not told otherwise.

    * src/c++11/debug.cc [_GLIBCXX_HAVE_EXECINFO_H]: Include execinfo.h.
    [_GLIBCXX_HAVE_EXECINFO_H](_Error_formatter::_M_error): Render 
backtrace.

François

diff --git a/libstdc++-v3/src/c++11/debug.cc b/libstdc++-v3/src/c++11/debug.cc
index 3a1558b..cd1b43d 100644
--- a/libstdc++-v3/src/c++11/debug.cc
+++ b/libstdc++-v3/src/c++11/debug.cc
@@ -40,6 +40,10 @@
 
 #include <cxxabi.h> // for __cxa_demangle
 
+#if defined _GLIBCXX_HAVE_EXECINFO_H
+# include <execinfo.h> // for backtrace
+#endif
+
 #include "mutex_pool.h"
 
 using namespace std;
@@ -1048,6 +1052,29 @@ namespace __gnu_debug
 	print_literal(ctx, "\n");
       }
 
+#if defined _GLIBCXX_HAVE_EXECINFO_H
+    {
+      void* stack[32];
+      int nb = backtrace(stack, 32);
+
+      // Note that we skip current method symbol.
+      if (nb > 1)
+	{
+	  print_literal(ctx, "Backtrace:\n");
+	  auto symbols = backtrace_symbols(stack, nb);
+	  for (int i = 1; i < nb; ++i)
+	    {
+	      print_word(ctx, symbols[i]);
+	      print_literal(ctx, "\n");
+	    }
+
+	  free(symbols);
+	  ctx._M_first_line = true;
+	  print_literal(ctx, "\n");
+	}
+    }
+#endif
+
     print_literal(ctx, "Error: ");
 
     // Print the error message