Track all variables for execution of function in gdb

I want to track the state of all the variables in a function in C.

I know I can use info commands in gdb to get all the variables state at the current context.

And I can use gdbinit to automate the gdb.

But what I want to do is set a breakpoint at the function and then after executing each line print execute the info command.

Basically, I want to set 2 breakpoints: one at the start of a function and one at the end of the same function(I don't know how to this) and execute line-by-line between these 2 points.

I want something like this in my gdbinit:

b <func_name>
commands
while <inside the function>:
   info locals
   next
end
run

Is there a way to have the while loop shown above?

Solution

Basically, I want to set 2 breakpoints: one at the start of a function and one at the end of the same function(I don't know how to this) and execute line-by-line between these 2 points.

You can find how to set the breakpoint at the end of the function here. However, that isn't necessary here.

You can use $_caller_is() GDB convenience function to finish executing current routine, and stop after it has returned.

Example:

int fn()
{
  int sum = 0;
  for (int j = 0; j < 5; j++) {
    sum += j;
  }
  return sum;
}

int main()
{
  return fn() - 10;
}

And now GDB session:

gdb -q ./a.out
Reading symbols from ./a.out...
(gdb) b 4
Breakpoint 1 at 0x1130: file t.c, line 4.
(gdb) run
Starting program: /tmp/a.out

Breakpoint 1, fn () at t.c:4
4     for (int j = 0; j < 5; j++) {
(gdb) while $_caller_is("main")
 >info locals
 >next
 >end
j = 1431654464
sum = 0
5       sum += j;
j = 0
sum = 0
4     for (int j = 0; j < 5; j++) {
j = 0
sum = 0
5       sum += j;
j = 1
sum = 0
4     for (int j = 0; j < 5; j++) {
j = 1
sum = 1
5       sum += j;
j = 2
sum = 1
4     for (int j = 0; j < 5; j++) {
j = 2
sum = 3
5       sum += j;
j = 3
sum = 3
4     for (int j = 0; j < 5; j++) {
j = 3
sum = 6
5       sum += j;
j = 4
sum = 6
4     for (int j = 0; j < 5; j++) {
j = 4
sum = 10
7     return sum;
sum = 10
8   }
sum = 10
main () at t.c:12
12    return fn() - 10;
(gdb) q

P.S. For all but toy problems, this method of debugging will be both grossly inefficient and insufficient (it is rare for the interesting state to be captured entirely by local variables).