GCC does not display line number information even with the -g option

Question

I built and installed GCC 4.8.1 from the source:

$ gcc -v Using built-in specs. COLLECT_GCC=gcc COLLECT_LTO_WRAPPER=/usr/local/libexec/gcc/x86_64-unknown-linux-gnu/4.8.1/lto-wrapper Target: x86_64-unknown-linux-gnu Configured with: ./configure --disable-multilib Thread model: posix gcc version 4.8.1 (GCC) 

And I wrote a simple useless program:

 $ cat hw.c #include <stdio.h> void foo() { int a; scanf("%d", &a); /* So I can press ctrl+c here. */ printf("Hello world!\n"); } int main() { foo(); } 

Now I will compile this:

 $ gcc -g -O0 hw.c -o hw 

Then he started debugging it using GDB:

 $ gdb hw GNU gdb (Ubuntu/Linaro 7.4-2012.04-0ubuntu2.1) 7.4-2012.04 Copyright (C) 2012 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html> This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. Type "show copying" and "show warranty" for details. This GDB was configured as "x86_64-linux-gnu". For bug reporting instructions, please see: <http://bugs.launchpad.net/gdb-linaro/>... Reading symbols from /home/calmarius/workdir/crucible/hw/hw...done. (gdb) 

Run it and immediately Ctrl + C:

 (gdb) run Starting program: /home/dcsirmaz/workdir/crucible/hw/hw ^C Program received signal SIGINT, Interrupt. 0x00007ffff7b018b0 in __read_nocancel () at ../sysdeps/unix/syscall-template.S:82 82 ../sysdeps/unix/syscall-template.S: Nincs ilyen fájl vagy könyvtár. 

I got function names in backtrace, but there were no line numbers in my code:

 (gdb) bt #0 0x00007ffff7b018b0 in __read_nocancel () at ../sysdeps/unix/syscall-template.S:82 #1 0x00007ffff7a95ff8 in _IO_new_file_underflow (fp=0x7ffff7dd4340) at fileops.c:619 #2 0x00007ffff7a9703e in _IO_default_uflow (fp=0x7ffff7dd4340) at genops.c:440 #3 0x00007ffff7a74fb6 in _IO_vfscanf_internal (s=<optimized out>, format=<optimized out>, argptr=0x7fffffffe018, errp=0x0) at vfscanf.c:620 #4 0x00007ffff7a790bd in __isoc99_scanf (format=<optimized out>) at isoc99_scanf.c:37 #5 0x000000000040054e in foo () #6 0x0000000000400568 in main () 

Something went wrong? Maybe this is something with the configuration?

Answer 1

Your gdb is too old - you need the later gdb (I use 7.6) to understand the debug information generated by gcc 4.8.1

Answer 2

GCC usually uses the dwarf as the main debug file format, you need to enable dwarf support when creating gcc with the --with-dwarf2 .

When creating a compiled object, you can use -ggdb instead of -g , which is a more specific solution, but only for gdb .