[Bug c++/34152] New: Erratic behaviour: Exception translation (throw from signal handlers)

[Bug c++/34152] New: Erratic behaviour: Exception translation (throw from signal handlers)

[asteinarson at gmail dot com]

In our application we want to translate synchronous signals (such as SIGSEGV)
to C++ exceptions. 

The method is to use throw directly from either:

1 - From the signal handler itself.
2 - From a function called by the signal handler.

I'm having trouble getting this to work reliably. Test program attached below.

Building and running:

  $ g++ sigthrow.cpp -fnon-call-exceptions -fexceptions
  $ a.out
  terminate called after throwing an instance of 'char const*'
  Aborted (core dumped)
  $ 

Removing option -fnon-call-exceptions gives: 

  $ g++ sigthrow.cpp -fexceptions
  $ a.out
  ~StructWithDtor: Count 0
  Caught exception

So it works, except the frame that generated the exception is not cleaned up
(it should call a destructor for another instance of StructWithDtor).

The pattern seems to be:
1 - If the function generating the signal has objects to unwind, this is always
missed. 
2 - Also, when compiled with -fnon-call-exceptions the program often (not
always) aborts.
3 - If the function generating the signal does not have objects to unwind it
goes well (with or without -fnon-call-exceptions)


Are there some other compiler option to make this work? Something to be done in
the signal handler?

So far I haven't found any working examples of this functionality on the web.
But others have found similar difficulties. 

What is the status of this? 

It's an important feature when using plugins, script interpreters and linking
with code from other languages.

Regards
// ATS.

----------------- source -------------------------------


#include <stdio.h>
#include <csignal>
#include <unistd.h>
#include <sys/syscall.h>

typedef void(*stSignalHandlerFn)(int);

struct old_i386_kernel_sigaction {
        stSignalHandlerFn k_sa_handler;
        unsigned long k_sa_mask;
        unsigned long k_sa_flags;
        void (*sa_restorer) (void);
};

void stSigSegvHandler( int dummy ){
        void **_p = (void **)&dummy;
        struct sigcontext_struct *_regs = (struct sigcontext_struct *)++_p;
        throw "SIGSEGV signaled";
}


int g_cnt;
struct StructWithDtor { 
    StructWithDtor() : m_cnt(g_cnt++) { }
    ~StructWithDtor(){ printf("~StructWithDtor: Count %d\n", m_cnt); }
    int m_cnt;
};



int FuncNested1( int *pi ){
    StructWithDtor swd;
    return *pi;
}

int FuncTop( int *pi ){
    StructWithDtor swd;
    return FuncNested1( pi );
}

int main( int argc, const char* argv[] ) {

    // Install a SIGSEGV handler using syscall 
    struct old_i386_kernel_sigaction kact;                              
    kact.k_sa_handler = stSigSegvHandler;               
    kact.k_sa_mask = 0;                                 
    kact.k_sa_flags = 0;                                
    syscall( SYS_sigaction, SIGSEGV, &kact, NULL );

    // Trigger SIGSEGV 
    try {
        FuncTop( NULL );
    }catch( ... ){
        puts( "Caught exception\n" );
    }

}


-- 
           Summary: Erratic behaviour: Exception translation (throw from
                    signal handlers)
           Product: gcc
           Version: 4.1.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: asteinarson at gmail dot com
 GCC build triplet: Linux Ubuntu 7.10, X86-32, gcc 4.1.3 (Ubuntu default)
  GCC host triplet: Linux Ubuntu 7.10, X86-32, gcc 4.1.3 (Ubuntu default)
GCC target triplet: Linux Ubuntu 7.10, X86-32, gcc 4.1.3 (Ubuntu default)


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34152

[Bug c++/34152] Erratic behaviour: Exception translation (throw from signal handlers)

[asteinarson at gmail dot com]

------- Comment #1 from asteinarson at gmail dot com  2007-11-19 16:21 -------
I found something out. If I add a further function call to FuncNested1:

int FuncNested2(  ){
    StructWithDtor swd;
    return 0;
} 

int FuncNested1( int *pi ){
    StructWithDtor swd;
    FuncNested2( );   // This trigger unwind table generation
    return *pi;
}

then it works. It seems that FuncNested1 in the first form: 

int FuncNested1( int *pi ){
    StructWithDtor swd;
    return *pi;
}

never generates any unwinding information (since it doesn't call other
functions) and when SIGSEGV happens inside it, it cannot find any unwind tables
and C++ run-time bails out. I can understand the logic behind this, but it
certainly made my first test case fail miserably.

In a realworld app, the optimization is probably OK, since a function
generating the signal is likely to contain other function calls (not bullet
proof).

It is possible to interpret -asynchronous-unwind-tables to support this but
that option changes nothing for my test case.

An option -always-generate-unwind-tables would be useful in this case (but
probably results in a larger executable).

Regards
// ATS.


-- 

asteinarson at gmail dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |asteinarson at gmail dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34152

[Bug c++/34152] Erratic behaviour: Exception translation (throw from signal handlers)

[phelps at gnusto dot com]

------- Comment #2 from phelps at gnusto dot com  2007-12-11 10:38 -------
Created an attachment (id=14728)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=14728&action=view)
proposed fix

I'm seeing similar behavior on x86-64 with both g++-4.1.3 (ubuntu-7.10 dist)
and g++-4.2.2 build from sources.  I spent some time in the debugger and I've
identified the problem and a fix.

It looks like the problem first appeared in r115654.  The change to
eh_personality.cc guards a call to _Unwind_GetIPInfo with the preprocessor
macro HAVE_GETIPINFO.  Unfortunately, that macro HAVE_GETIPINFO is never
defined in c++config.h; _GLIBCXX_HAVE_GETIPINFO is.

The attached patch (against gcc-4.2.2) fixes this issue and the resulting
libstdc++.so.6.0.9 produces the desired behavior.

Thanks,
-Ted


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34152

[Bug c++/34152] Erratic behaviour: Exception translation (throw from signal handlers)

[phelps at gnusto dot com]

------- Comment #3 from phelps at gnusto dot com  2007-12-11 10:43 -------
Added Steve Ellcey to the CC as he's the author of r115654.  Hope that's not
rude.

Thanks,
-Ted


-- 

phelps at gnusto dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |sje at cup dot hp dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34152

[Bug c++/34152] Erratic behaviour: Exception translation (throw from signal handlers)

[asteinarson at gmail dot com]

------- Comment #4 from asteinarson at gmail dot com  2007-12-11 17:55 -------
(In reply to comment #2)
> Created an attachment (id=14728)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=14728&action=view) [edit]
> proposed fix
> 
> I'm seeing similar behavior on x86-64 with both g++-4.1.3 (ubuntu-7.10 dist)
> and g++-4.2.2 build from sources.  I spent some time in the debugger and I've
> identified the problem and a fix.
>
> ...
>
> The attached patch (against gcc-4.2.2) fixes this issue and the resulting
> libstdc++.so.6.0.9 produces the desired behavior.
> 

Good to see a solution. When/where is it reasonable to expect the patch in a
release? Would it go into 4.2 or 4.3 or would it be backported to 4.1 series?

Regards
// ATS


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34152

[Bug c++/34152] Erratic behaviour: Exception translation (throw from signal handlers)

[phelps at gnusto dot com]

------- Comment #5 from phelps at gnusto dot com  2007-12-11 22:30 -------
Created an attachment (id=14732)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=14732&action=view)
minimal test case

This attachment contains a minimal C++ program that exhibits the behavior.  The
program should exit with a return code of 0, but without the patch above it
produces the following output:

    terminate called after throwing an instance of 'int'

-Ted


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34152

[Bug c++/34152] Erratic behaviour: Exception translation (throw from signal handlers)

[jakub at gcc dot gnu dot org]

------- Comment #6 from jakub at gcc dot gnu dot org  2007-12-11 22:49 -------
Benjamin, the patch in #c4 looks good to me and this is a very severe bug,
could
you please review the patch and apply if you agree?
Wonder what kind of testing was done before r115654 commit :(.


-- 

jakub at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bkoz at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34152

[Bug c++/34152] Erratic behaviour: Exception translation (throw from signal handlers)

[asteinarson at gmail dot com]

------- Comment #7 from asteinarson at gmail dot com  2008-01-06 17:02 -------
(In reply to comment #2)
> Created an attachment (id=14728)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=14728&action=view) [edit]
> proposed fix
> 
> I'm seeing similar behavior on x86-64 with both g++-4.1.3 (ubuntu-7.10 dist)
> and g++-4.2.2 build from sources.  I spent some time in the debugger and I've
> identified the problem and a fix.
> 

I've applied this path to GCC 4.3.0 (as of 2008-01-04). Unfortunately the
problem is still there for me. Both in the original test case and in the
non-call-except-cpp test case. 

Regards
// ATS

> 
> Thanks,
> -Ted
> 


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34152

[Bug c++/34152] Erratic behaviour: Exception translation (throw from signal handlers)

[jakub at gcc dot gnu dot org]

------- Comment #8 from jakub at gcc dot gnu dot org  2008-01-06 20:26 -------
Subject: Bug 34152

Author: jakub
Date: Sun Jan  6 20:25:57 2008
New Revision: 131361

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=131361
Log:
        PR c++/34152
        * libsupc++/eh_personality.cc (PERSONALITY_FUNCTION): Check
        _GLIBCXX_HAVE_GETIPINFO instead of HAVE_GETIPINFO.

Modified:
    trunk/libstdc++-v3/ChangeLog
    trunk/libstdc++-v3/libsupc++/eh_personality.cc


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34152

[Bug c++/34152] Erratic behaviour: Exception translation (throw from signal handlers)

[asteinarson at gmail dot com]

------- Comment #9 from asteinarson at gmail dot com  2008-01-06 23:18 -------
(In reply to comment #8)
> Subject: Bug 34152
> 
> Author: jakub
> Date: Sun Jan  6 20:25:57 2008
> New Revision: 131361
> 
> URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=131361
> Log:
>         PR c++/34152
>         * libsupc++/eh_personality.cc (PERSONALITY_FUNCTION): Check
>         _GLIBCXX_HAVE_GETIPINFO instead of HAVE_GETIPINFO.

I've checked this. From line 446 of libsupc++/eh_personality.cc: 

  // Parse the LSDA header.
  p = parse_lsda_header (context, language_specific_data, &info);
  info.ttype_base = base_of_encoded_value (info.ttype_encoding, context);
#ifdef _GLIBCXX_HAVE_GETIPINFO
  ip = _Unwind_GetIPInfo (context, &ip_before_insn);
#else
  ip = _Unwind_GetIP (context);
#endif

I've rebuild with the patch in a clean directory. g++ --version gives: 

$ g++43 --version
g++43 (GCC) 4.3.0 20080104 (experimental)


Regards
// ATS

> 
> Modified:
>     trunk/libstdc++-v3/ChangeLog
>     trunk/libstdc++-v3/libsupc++/eh_personality.cc
> 


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34152

[Bug c++/34152] Erratic behaviour: Exception translation (throw from signal handlers)

[asteinarson at gmail dot com]

------- Comment #10 from asteinarson at gmail dot com  2008-01-07 13:24 -------
(In reply to comment #9)
> (In reply to comment #8)
> > Subject: Bug 34152
> > 
> >         * libsupc++/eh_personality.cc (PERSONALITY_FUNCTION): Check
> >         _GLIBCXX_HAVE_GETIPINFO instead of HAVE_GETIPINFO.
> 
> I've checked this. From line 446 of libsupc++/eh_personality.cc: 

The trouble was that the GCC 4.3 was linking executables to the old version of
libstdc++ (4.1). 

Setting LD_LIBRARY_PATH did the trick. Both test cases work now.

Regards
// ATS


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34152

[Bug c++/34152] Erratic behaviour: Exception translation (throw from signal handlers)

[jakub at gcc dot gnu dot org]

------- Comment #11 from jakub at gcc dot gnu dot org  2008-01-07 16:06 -------
Subject: Bug 34152

Author: jakub
Date: Mon Jan  7 16:05:27 2008
New Revision: 131376

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=131376
Log:
        PR c++/34152
        * libsupc++/eh_personality.cc (PERSONALITY_FUNCTION): Check
        _GLIBCXX_HAVE_GETIPINFO instead of HAVE_GETIPINFO.

Modified:
    branches/gcc-4_2-branch/libstdc++-v3/ChangeLog
    branches/gcc-4_2-branch/libstdc++-v3/libsupc++/eh_personality.cc


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34152

[Bug c++/34152] Erratic behaviour: Exception translation (throw from signal handlers)

[phelps at gnusto dot com]

------- Comment #12 from phelps at gnusto dot com  2008-01-09 05:53 -------
re: comment #7, could you double-check with ldd that your application is
picking up the right libstdc++.so?  You may have to fiddle with your
LD_LIBRARY_PATH to make it do so.

-Ted


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34152

[Bug c++/34152] Erratic behaviour: Exception translation (throw from signal handlers)

[phelps at gnusto dot com]

------- Comment #13 from phelps at gnusto dot com  2008-01-09 05:54 -------
re: comment #12 -- sorry, just read comment #10.  Ignore me.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34152

[Bug c++/34152] Erratic behaviour: Exception translation (throw from signal handlers)

[pinskia at gcc dot gnu dot org]

------- Comment #14 from pinskia at gcc dot gnu dot org  2008-03-12 16:14 -------
*** Bug 35555 has been marked as a duplicate of this bug. ***


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34152

[Bug c++/34152] Erratic behaviour: Exception translation (throw from signal handlers)

[asteinarson at gmail dot com]

------- Comment #15 from asteinarson at gmail dot com  2008-03-12 16:41 -------
I had missed to use the flag -fnon-call-exceptions.  

With that enabled it works as it should. 

Regards
// ATS


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34152

[Bug c++/34152] Erratic behaviour: Exception translation (throw from signal handlers)

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34152

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
                 CC|gcc-bugs at gcc dot gnu.org |
         Resolution|                            |FIXED

--- Comment #16 from Paolo Carlini <paolo.carlini at oracle dot com> 2011-11-07 16:27:49 UTC ---
So, fixed long time ago.