[PATCH] libstdc++: Deliver names of C functions in <stacktrace>

[PATCH] libstdc++: Deliver names of C functions in <stacktrace>

[Björn Schäpers]

From: Björn Schäpers <bjoern@hazardy.de>

One could add (), these are not part of __name. One could also try to
check upfront if __cxa_demangle should be called at all.

-- >8 --

Tested on i686-w64-mingw32.

__cxa_demangle is only to demangle C++ names, for all C functions,
extern "C" functions, and including main it returns -2, in that case
just adapt the given name. Otherwise it's kept empty, which doesn't look
nice in the stacktrace.

libstdc++-v3/ChangeLog:

	* include/std/stacktrace (stacktrace_entry::_S_demangle): Use
	raw __name if __cxa_demangle could not demangle it.

Signed-off-by: Björn Schäpers <bjoern@hazardy.de>
---
 libstdc++-v3/include/std/stacktrace | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/libstdc++-v3/include/std/stacktrace b/libstdc++-v3/include/std/stacktrace
index 83c6463b0d8..6d4051b9f5b 100644
--- a/libstdc++-v3/include/std/stacktrace
+++ b/libstdc++-v3/include/std/stacktrace
@@ -217,8 +217,15 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       int __status;
       char* __str = __cxxabiv1::__cxa_demangle(__name, nullptr, nullptr,
 					       &__status);
-      if (__status == 0)
+      switch (__status)
+      {
+      case 0:
 	__s = __str;
+	break;
+      case -2:
+	__s = __name;
+	break;
+      }
       __builtin_free(__str);
       return __s;
     }
-- 
2.38.1

Re: [PATCH] libstdc++: Deliver names of C functions in <stacktrace>

[François Dumont]

On 12/12/22 18:56, Björn Schäpers wrote:
> From: Björn Schäpers <bjoern@hazardy.de>
>
> One could add (), these are not part of __name. One could also try to
> check upfront if __cxa_demangle should be called at all.
>
> -- >8 --
>
> Tested on i686-w64-mingw32.
>
> __cxa_demangle is only to demangle C++ names, for all C functions,
> extern "C" functions, and including main it returns -2, in that case
> just adapt the given name. Otherwise it's kept empty, which doesn't look
> nice in the stacktrace.
>
> libstdc++-v3/ChangeLog:
>
> 	* include/std/stacktrace (stacktrace_entry::_S_demangle): Use
> 	raw __name if __cxa_demangle could not demangle it.
>
> Signed-off-by: Björn Schäpers <bjoern@hazardy.de>
> ---
>   libstdc++-v3/include/std/stacktrace | 9 ++++++++-
>   1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/libstdc++-v3/include/std/stacktrace b/libstdc++-v3/include/std/stacktrace
> index 83c6463b0d8..6d4051b9f5b 100644
> --- a/libstdc++-v3/include/std/stacktrace
> +++ b/libstdc++-v3/include/std/stacktrace
> @@ -217,8 +217,15 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>         int __status;
>         char* __str = __cxxabiv1::__cxa_demangle(__name, nullptr, nullptr,
>   					       &__status);
> -      if (__status == 0)
> +      switch (__status)
> +      {
> +      case 0:
>   	__s = __str;
> +	break;
> +      case -2:
> +	__s = __name;
> +	break;
> +      }
>         __builtin_free(__str);
>         return __s;
>       }

why not just using __name if __status != 0 ? Everything seems better 
than an empty string, no ?

This is what I've done in src/c++11/debug.cc.

[PATCH] libstdc++: Deliver names of C functions in <stacktrace>

[Björn Schäpers]

From: Björn Schäpers <bjoern@hazardy.de>

One could add (), these are not part of __name. One could also try to
check upfront if __cxa_demangle should be called at all.

-- >8 --

Tested on i686-w64-mingw32.

__cxa_demangle is only to demangle C++ names, for all C functions,
extern "C" functions, and including main it returns -2, in that case
just adapt the given name. Otherwise it's kept empty, which doesn't look
nice in the stacktrace.

libstdc++-v3/ChangeLog:

	* include/std/stacktrace (stacktrace_entry::_S_demangle): Use
	raw __name if __cxa_demangle could not demangle it.

Signed-off-by: Björn Schäpers <bjoern@hazardy.de>
---
 libstdc++-v3/include/std/stacktrace | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/libstdc++-v3/include/std/stacktrace b/libstdc++-v3/include/std/stacktrace
index 83c6463b0d8..5baf2dcdaca 100644
--- a/libstdc++-v3/include/std/stacktrace
+++ b/libstdc++-v3/include/std/stacktrace
@@ -219,6 +219,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 					       &__status);
       if (__status == 0)
 	__s = __str;
+      else
+	__s = __name;
       __builtin_free(__str);
       return __s;
     }
-- 
2.38.1

Re: [PATCH] libstdc++: Deliver names of C functions in <stacktrace>

[Jonathan Wakely]

On Tue, 13 Dec 2022 at 21:03, Björn Schäpers <gcc@hazardy.de> wrote:
>
> From: Björn Schäpers <bjoern@hazardy.de>
>
> One could add (), these are not part of __name. One could also try to
> check upfront if __cxa_demangle should be called at all.


Thanks for the patch, I'll push this.

I think we do want to check whether to call __cxa_demangle, because
otherwise an extern "C" function called simply "g" will get demangled
to "__float128" and that's not right!

So I think we should check whether the function name starts with "_Z"
which indicates a C++ function name. That can be improved later
though.



>
> -- >8 --
>
> Tested on i686-w64-mingw32.
>
> __cxa_demangle is only to demangle C++ names, for all C functions,
> extern "C" functions, and including main it returns -2, in that case
> just adapt the given name. Otherwise it's kept empty, which doesn't look
> nice in the stacktrace.
>
> libstdc++-v3/ChangeLog:
>
>         * include/std/stacktrace (stacktrace_entry::_S_demangle): Use
>         raw __name if __cxa_demangle could not demangle it.
>
> Signed-off-by: Björn Schäpers <bjoern@hazardy.de>
> ---
>  libstdc++-v3/include/std/stacktrace | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/libstdc++-v3/include/std/stacktrace b/libstdc++-v3/include/std/stacktrace
> index 83c6463b0d8..5baf2dcdaca 100644
> --- a/libstdc++-v3/include/std/stacktrace
> +++ b/libstdc++-v3/include/std/stacktrace
> @@ -219,6 +219,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>                                                &__status);
>        if (__status == 0)
>         __s = __str;
> +      else
> +       __s = __name;
>        __builtin_free(__str);
>        return __s;
>      }
> --
> 2.38.1
>