Stack tracing on Linux ?

[Georg Wrede]

Simon Gomizelj wrote:
> On Thu, 02 Apr 2009 04:56:46 -0400, Georg Wrede <georg.wrede at iki.fi> wrote:
> 
>> With gdb I can either debug a core dump or an actual running process. 
>> For example, with
>>
>> import std.stdio;
>>
>> int main()
>> {
>>      readWrite();
>>      return 8;
>> }
>>
>> void readWrite()
>> {
>>      auto line = readln();   // here it waits, and that's when I debug
>>                              // in another window
>>      write("Rivi oli: ", line);
>> }
>>
>> I get the following stack trace (it looks the same whether I debug a 
>> core dump or a running instance)
>>
>> #0  0x00251416 in __kernel_vsyscall ()
>> #1  0x00591a93 in __read_nocancel () from /lib/libc.so.6
>> #2  0x00528cee in _IO_new_file_underflow (fp=0x62e420) at fileops.c:598
>> #3  0x0052c17a in __underflow (fp=0x62e420) at genops.c:361
>> #4  0x0051e648 in _IO_getdelim (lineptr=0xbf94ec8c, n=0xbf94ec90,
>>      delimiter=10, fp=0x62e420) at iogetdelim.c:79
>> #5  0x080505bb in _D3std5stdio6readlnFPS3std1c5stdio6_iobufKAawZk ()
>> #6  0x080504d0 in _D3std5stdio6readlnFPS3std1c5stdio6_iobufwZAya ()
>> #7  0x0804931a in _D5read29readWriteFZv ()
>> #8  0x00000000 in ?? ()
>>
>> This is not perfect, 5..7 are functions written in D, but main is 
>> missing. Then, trying to examine a core dump from something that gets 
>> a segfault, I wrote the following, expecting that I'd get a grandiose 
>> stack trace
>>
>>
>> $ cat npe.d
>> import std.stdio;
>>
>> int main()
>> {
>>      return foo(3);
>> }
>>
>> int foo(int a)
>> {
>>      return 1 + bar(a - 3);
>> }
>>
>> int bar(int b)
>> {
>>      return 1 + car(b - 3);
>> }
>>
>> int car(int c)
>> {
>>      return 1 + dar(c - 3);
>> }
>>
>> int dar(int d)
>> {
>>      return 1 + * cast(int*) d; // null pointer exception
>> }
>>
>>
>>
>> Turns out I got zilch!
>>
>> #0  0x08049118 in _D3npe3darFiZi ()
>> #1  0xfffffffa in ?? ()
>>
>> I have DMD on Fedora 10, and used
>> dmd -g -debug -v read2.d
>> to compile. Incidentally, using
>> dmd -gc -debug -v read2.d
>> does seem to give the same stack trace.
>>
> 
> While I can't explain why gdb and dmd don't seem to work nicely 
> together, you'd have much better luck using ldc.
> Compiling with ldc, this is the backtrace I got when debugging read2.d 
> on my maching (and is what you're probably looking for):
> 
> (gdb) run
> Starting program: /data/Code/D/error
> [Thread debugging using libthread_db enabled]
> [New Thread 0xb7d656c0 (LWP 14104)]
> 
> Program received signal SIGSEGV, Segmentation fault.
> [Switching to Thread 0xb7d656c0 (LWP 14104)]
> 0x080495fe in _D5error3darFiZi (d=-6) at error.d:23
> 23        return 1 + * cast(int*) d; // null pointer exception
> (gdb) backtrace
> #0  0x080495fe in _D5error3darFiZi (d=-6) at error.d:23
> #1  0x080495e3 in _D5error3carFiZi (c=-3) at error.d:18
> #2  0x080495c3 in _D5error3barFiZi (b=0) at error.d:13
> #3  0x080495a3 in _D5error3fooFiZi (a=3) at error.d:8
> #4  0x0804957d in _Dmain () at error.d:3
> #5  0x0804dd0a in _D6dmain24mainUiPPaPPaZi7runMainMFZv ()
> #6  0x0804d9c7 in _D6dmain24mainUiPPaPPaZi7tryExecMFDFZvZv ()
> #7  0x0804dd4d in _D6dmain24mainUiPPaPPaZi6runAllMFZv ()
> #8  0x0804d9c7 in _D6dmain24mainUiPPaPPaZi7tryExecMFDFZvZv ()
> #9  0x0804d946 in main ()

Ah, this looks nice. And the file name shows in the function names.

If everyone wasn't telling me it's a licence issue, I'd take it for 
granted there's a bug in DMD.