When a segmentation violation signal is handled, the function where
the SEGV happens is not available from the backtrace() call; this
of-course makes it less usefull, since the correct spot of the crash
cannot be found.

The program below shows the problem; the last frame available
before sigaction() is f5().  f5() calls the function crash(), which
results in a SIGSEGV.  When the call-stack is extracted, the frame for
crash() is not available.

When mapping addressess to function-name:line, one only knows which
function the crash happens in (by looking at the last line before
sigaction(), which will then point to a line with a function call.

Program:
#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <unistd.h>
#include <execinfo.h>

static void SignalHandler(int nSignal);
static void f1();
static void f2();
static void f3();
static void f4();
static void f5();
static void crash();

int
main()
{
  signal(SIGSEGV, SignalHandler);
  f1();
  return 0;
}

static void
SignalHandler(int nSignal)
{
  if ( SIGSEGV == nSignal ) {
    static bool bHere = false;
    if ( true == bHere ) {
      printf("Caught SIGSEGV while handling it -- aborting...\n");
      abort();
    }
    bHere = true;

    void* apFrames[256];
    const int nNumFramesFound =
      backtrace(apFrames, sizeof(apFrames)/sizeof(apFrames[0]));
    char** apzFrameNames = backtrace_symbols(apFrames, nNumFramesFound);
    printf("Frame address \t Symbol\n"
           "--------------------------------------------------------------\n");
    for ( int iFrame = 0; iFrame < nNumFramesFound; ++iFrame ) {
      const unsigned int nAddress = (unsigned int)apFrames[iFrame];
      printf("0x%08x \t +%s;\n", nAddress, apzFrameNames[iFrame]);
    }
    free(apzFrameNames);

    bHere = false;
    abort();
  }
}

static void f1()
{
  f2();
}
static void f2()
{
  f3();
}
static void f3()
{
  f4();
}
static void f4()
{
  f5();
}
static void f5()
{
  crash();
}
static void crash()
{
  char* oops = 0;
  *oops = 0;
}


This is the output caused by the program:
Frame address    Symbol
--------------------------------------------------------------
0x0804871b       +[0x804871b];
0x4009ec48       +/lib/libc.so.6(sigaction+0x268) [0x4009ec48];
0x08048853       +[0x8048853];
0x0804883f       +[0x804883f];
0x08048827       +[0x8048827];
0x08048813       +[0x8048813];
0x080487ff       +[0x80487ff];
0x080486bd       +[0x80486bd];
0x400989cb       +/lib/libc.so.6(__libc_start_main+0xff) [0x400989cb];
0x080485e1       +[0x80485e1];
Aborted (core dumped)


(This has also been tested on Red Hat Linux v7.0 with the latest glibc
package, and the problem is present there as well.)