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

[Jonathan Wakely <jwakely@redhat.com>]

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On Wed, 30 Nov 2022 at 11:57, Jonathan Wakely <jwakely@redhat.com> wrote:
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>
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> On Wed, 30 Nov 2022 at 11:54, Jonathan Wakely <jwakely@redhat.com> wrote:
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>>
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>> On Wed, 30 Nov 2022 at 06:04, François Dumont via Libstdc++ <libstdc++@gcc.gnu.org> wrote:
>>>
>>> Good catch, then we also need this patch.
>>
>>
>> Is it worth printing an error? If we can't show the backtrace because of an error, we can just print nothing there.
>>
>> We also need to pass an error handler to the __glibcxx_backtrace_create_state call in formatter.h.
>>
>> Now that I look at this code again, why do we need the _M_backtrace_full member? It's always set to the same thing, why can't we just call that function directly?
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> Oh right, I remember now ... because otherwise the libstdc++.so library needs the definition of __glibcxx_backtrace_full.

I'm testing the attached patch.


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>> And I think we should use threaded=1 for the __glibcxx_backtrace_create_state call.
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>> So like the attached patch.
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commit 6c9cc05dc097f6ee66f18731a6247cce36823d54
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Wed Nov 30 12:32:53 2022

    libstdc++: Pass error handler to libbacktrace functions
    
    Also pass threaded=1 to __glibcxx_backtrace_create_state and remove some
    of the namespace scope declarations.
    
    libstdc++-v3/ChangeLog:
    
            * include/debug/formatter.h [_GLIBCXX_DEBUG_BACKTRACE]
            (_Error_formatter::_Error_formatter): Pass error handler to
            __glibcxx_backtrace_create_state. Pass 1 for threaded argument.
            (_Error_formatter::_S_err): Define empty function.
            * src/c++11/debug.cc (_Error_formatter::_M_error): Pass error
            handler to __glibcxx_backtrace_full.

diff --git a/libstdc++-v3/include/debug/formatter.h b/libstdc++-v3/include/debug/formatter.h
index f120163c6d4..e8a83a21bde 100644
--- a/libstdc++-v3/include/debug/formatter.h
+++ b/libstdc++-v3/include/debug/formatter.h
@@ -32,32 +32,17 @@
 #include <bits/c++config.h>
 
 #if _GLIBCXX_HAVE_STACKTRACE
-struct __glibcxx_backtrace_state;
-
 extern "C"
 {
-  __glibcxx_backtrace_state*
+  struct __glibcxx_backtrace_state*
   __glibcxx_backtrace_create_state(const char*, int,
 				   void(*)(void*, const char*, int),
 				   void*);
-
-  typedef int (*__glibcxx_backtrace_full_callback) (
-    void*, __UINTPTR_TYPE__, const char *, int, const char*);
-
-  typedef void (*__glibcxx_backtrace_error_callback) (
-    void*, const char*, int);
-
-  typedef int (*__glibcxx_backtrace_full_func) (
-    __glibcxx_backtrace_state*, int,
-    __glibcxx_backtrace_full_callback,
-    __glibcxx_backtrace_error_callback,
-    void*);
-
   int
   __glibcxx_backtrace_full(
-    __glibcxx_backtrace_state*, int,
-    __glibcxx_backtrace_full_callback,
-    __glibcxx_backtrace_error_callback,
+    struct __glibcxx_backtrace_state*, int,
+    int (*)(void*, __UINTPTR_TYPE__, const char *, int, const char*),
+    void (*)(void*, const char*, int),
     void*);
 }
 #endif
@@ -609,10 +594,10 @@ namespace __gnu_debug
     , _M_function(__function)
 #if _GLIBCXX_HAVE_STACKTRACE
 # ifdef _GLIBCXX_DEBUG_BACKTRACE
-    , _M_backtrace_state(__glibcxx_backtrace_create_state(0, 0, 0, 0))
+    , _M_backtrace_state(__glibcxx_backtrace_create_state(0, 1, _S_err, 0))
     , _M_backtrace_full(&__glibcxx_backtrace_full)
 # else
-    , _M_backtrace_state()
+    , _M_backtrace_state(0)
 # endif
 #endif
     { }
@@ -631,8 +616,12 @@ namespace __gnu_debug
     const char*		_M_text;
     const char*		_M_function;
 #if _GLIBCXX_HAVE_STACKTRACE
-    __glibcxx_backtrace_state*		_M_backtrace_state;
-    __glibcxx_backtrace_full_func	_M_backtrace_full;
+    struct __glibcxx_backtrace_state*		_M_backtrace_state;
+    // TODO: Remove _M_backtrace_full after __glibcxx_backtrace_full is moved
+    // from libstdc++_libbacktrace.a to libstdc++.so:
+    __decltype(&__glibcxx_backtrace_full)	_M_backtrace_full;
+
+    static void _S_err(void*, const char*, int) { }
 #endif
 
   public:
diff --git a/libstdc++-v3/src/c++11/debug.cc b/libstdc++-v3/src/c++11/debug.cc
index 9eda38023f7..c08eaa7f921 100644
--- a/libstdc++-v3/src/c++11/debug.cc
+++ b/libstdc++-v3/src/c++11/debug.cc
@@ -1193,7 +1193,7 @@ namespace __gnu_debug
       {
 	print_literal(ctx, "Backtrace:\n");
 	_M_backtrace_full(
-	  _M_backtrace_state, 1, print_backtrace, nullptr, &ctx);
+	  _M_backtrace_state, 1, print_backtrace, _S_err, &ctx);
 	ctx._M_first_line = true;
 	print_literal(ctx, "\n");
       }