GDB: break if variable equal value

Question

I like to make GDB set a break point when a variable equal some value I set, I tried this example:

#include 
main()
{ 
     int i = 0;
     fo         


        

Answer 1

First, you need to compile your code with appropriate flags, enabling debug into code.

$ gcc -Wall -g -ggdb -o ex1 ex1.c

then just run you code with your favourite debugger

$ gdb ./ex1

show me the code.

(gdb) list
1   #include 
2   int main(void)
3   { 
4     int i = 0;
5     for(i=0;i<7;++i)
6       printf("%d\n", i);
7   
8     return 0;
9   }

break on lines 5 and looks if i == 5.

(gdb) b 5
Breakpoint 1 at 0x4004fb: file ex1.c, line 5.
(gdb) rwatch i if i==5
Hardware read watchpoint 5: i

checking breakpoints

(gdb) info b
Num     Type           Disp Enb Address            What
1       breakpoint     keep y   0x00000000004004fb in main at ex1.c:5
    breakpoint already hit 1 time
5       read watchpoint keep y                      i
    stop only if i==5

running the program

(gdb) c
Continuing.
0
1
2
3
4
Hardware read watchpoint 5: i

Value = 5
0x0000000000400523 in main () at ex1.c:5
5     for(i=0;i<7;++i)