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debugginggdb

gdb display using printf

gdb can use display to print an expression each step. I want to format the expression, using gdb's printf. How can I tell gdb to run a printf each step, similar to display?

Solution

  • You can use hook-next. Documentation.

    Example:

    // t.c
int main()
{
  int x = 2;
  x++;
  x += 3;
  x += 5;
  return x - 11;
}

    gcc -g t.c && gdb -q ./a.out
(gdb) start
(gdb) define hook-next
Type commands for definition of "hook-next".
End with a line saying just "end".
>printf "%08d\n", x
>end
(gdb) next
00032767        # <<-- x hasn't been initialized yet.
4         x++;
(gdb) next
00000002
5         x += 3;
(gdb)
00000003
6         x += 5;
(gdb)
00000006
7         return x - 11;
(gdb)
00000011
8       }
(gdb) q