[Bug libfortran/36044] user-requested backtrace

fxcoudert at gcc dot gnu dot org gcc-bugzilla@gcc.gnu.org
Sun Feb 22 22:33:00 GMT 2009



------- Comment #5 from fxcoudert at gcc dot gnu dot org  2009-02-22 22:33 -------
(In reply to comment #3)
> Try abort(). (Though I do not recall whether it works, I think it does.)

Does not work. abort() raises a SIGABRT, and we only catch SIGSEGV, SIGBUS,
SIGILL and SIGFPE.

>> Anyway I'm looking for a solution that keeps the
>> program running after the backtrace.

One such solution that I can see (other than adding a new intrinsic) is to
modify the library to also catch SIGUSR2 and generate a backtrace when it's
received (untested patch below); that way, a backtrace can be emitted without
the code stopping, either

  -- programmaticaly by calling the KILL and GETPID intrinsics, or the POSIX
functions via ISO_C_BINDING
  -- by the user sending the signal from another terminal, to know where his
program is stuck

The only issue I see with that is that SIGUSR2 is a symbolic constant, not
available in Fortran code, so that the user needs to know what (potentialy
nonportable) signal number it corresponds to.





diff -rpu libgfortran/runtime/compile_options.c
libgfortran.new/runtime/compile_options.c
--- libgfortran/runtime/compile_options.c       2009-02-22 23:25:25.000000000
+0100
+++ libgfortran.new/runtime/compile_options.c   2009-02-22 23:30:20.000000000
+0100
@@ -73,6 +73,13 @@ handler (int signum)
        desc = "Floating-point exception";
        break;
 #endif
+
+#if defined(SIGUSR2)
+      case SIGUSR2:
+       name = "SIGUSR2";
+       desc = "User-defined signal";
+       break;
+#endif
     }

   if (name)
@@ -80,6 +87,16 @@ handler (int signum)
   else
     st_printf ("\nProgram received signal %d.\n", signum);

+#if defined(SIGUSR2)
+  if (signum == SIGUSR2
+      && (options.backtrace == 1
+         || (options.backtrace == -1 && compile_options.backtrace == 1)))
+  {
+    show_backtrace ();
+    return;
+  }
+#endif
+
   sys_exit (5);
 }



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36044



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