Re: [PATCH] libstdc++: Add error handler for

[Björn Schäpers]

One could (for a manual test) always change libbacktrace to call the callback. 
Or invoke it on a platform where libbacktrace can't figure out the executable 
path on its own, like currently windows.

As for an automated test, I have no idea how to enforce that, without changing 
the code to be tested.

Björn.

Am 30.11.2022 um 07:04 schrieb François Dumont:
Good catch, then we also need this patch.

I still need to test it thought, just to make sure it compiles. Unless you have 
a nice way to force call to the error callback ?

François

On 29/11/22 22:41, Björn Schäpers wrote:
From: Björn Schäpers <bjo...@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();