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

[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 <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();
>