[PATCH] libstdc++: Add error handler for <stacktrace>

[Björn Schäpers]

From: Björn Schäpers <bjoern@hazardy.de>

Not providing an error handler results in a nullpointer dereference when
an error occurs.

libstdc++-v3/ChangeLog

	* include/std/stacktrace: Add __backtrace_error_handler and use
	it in all calls to libbacktrace.
---
 libstdc++-v3/include/std/stacktrace | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/libstdc++-v3/include/std/stacktrace b/libstdc++-v3/include/std/stacktrace
index e7cbbee5638..b786441cbad 100644
--- a/libstdc++-v3/include/std/stacktrace
+++ b/libstdc++-v3/include/std/stacktrace
@@ -85,6 +85,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
 #define __cpp_lib_stacktrace 202011L
 
+  inline void
+  __backtrace_error_handler(void*, const char*, int) {}
+
   // [stacktrace.entry], class stacktrace_entry
   class stacktrace_entry
   {
@@ -159,7 +162,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     _S_init()
     {
       static __glibcxx_backtrace_state* __state
-	= __glibcxx_backtrace_create_state(nullptr, 1, nullptr, nullptr);
+	= __glibcxx_backtrace_create_state(nullptr, 1,
+					   __backtrace_error_handler, nullptr);
       return __state;
     }
 
@@ -192,7 +196,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	  return __function != nullptr;
       };
       const auto __state = _S_init();
-      if (::__glibcxx_backtrace_pcinfo(__state, _M_pc, +__cb, nullptr, &__data))
+      if (::__glibcxx_backtrace_pcinfo(__state, _M_pc, +__cb,
+				       __backtrace_error_handler, &__data))
 	return true;
       if (__desc && __desc->empty())
 	{
@@ -201,8 +206,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	      if (__symname)
 		*static_cast<_Data*>(__data)->_M_desc = _S_demangle(__symname);
 	  };
-	  if (::__glibcxx_backtrace_syminfo(__state, _M_pc, +__cb2, nullptr,
-					    &__data))
+	  if (::__glibcxx_backtrace_syminfo(__state, _M_pc, +__cb2,
+					    __backtrace_error_handler, &__data))
 	    return true;
 	}
       return false;
@@ -252,7 +257,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	if (auto __cb = __ret._M_prepare()) [[likely]]
 	  {
 	    auto __state = stacktrace_entry::_S_init();
-	    if (__glibcxx_backtrace_simple(__state, 1, __cb, nullptr,
+	    if (__glibcxx_backtrace_simple(__state, 1, __cb,
+					   __backtrace_error_handler,
 					   std::__addressof(__ret)))
 	      __ret._M_clear();
 	  }
@@ -270,7 +276,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	if (auto __cb = __ret._M_prepare()) [[likely]]
 	  {
 	    auto __state = stacktrace_entry::_S_init();
-	    if (__glibcxx_backtrace_simple(__state, __skip + 1, __cb, nullptr,
+	    if (__glibcxx_backtrace_simple(__state, __skip + 1, __cb,
+					   __backtrace_error_handler,
 					   std::__addressof(__ret)))
 	      __ret._M_clear();
 	  }
@@ -294,7 +301,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	  {
 	    auto __state = stacktrace_entry::_S_init();
 	    int __err = __glibcxx_backtrace_simple(__state, __skip + 1, __cb,
-						   nullptr,
+						   __backtrace_error_handler,
 						   std::__addressof(__ret));
 	    if (__err < 0)
 	      __ret._M_clear();
-- 
2.38.1