Can you take the "step" time in gdb?

Question

I am debugging a C library using gdb (gtk).

There is too slow function. I am trying to figure out which part of the function is causing a delay.

I understand that one option would be to enable manual code / recompilation for testing code segments, but is there a way to get the time taken to complete one step in gdb?

Answer 1

For quick and dirty profiling, you can put this fragment in your ~/.gdbinitfile:

define timeit                                                                                                                                                                             
    python import time
    python start_time = time.time()
    step
    python print("Call took {:.4f} ms".format(time.time() - start_time))
end
document timeit
    Time execution of next function
    Usage: timeit (or ti)
end

Here is an example of the function used timeit:

$ gdb --quiet --args ./can-daemon --config=../scripts/handlers.lua vcan0
Reading symbols from ./can-daemon...done.
(gdb) b main.cpp:548
Breakpoint 1 at 0x4c5bd4: file /home/evadeflow/projects/info4/can-daemon/src/main.cpp, line 548.
(gdb) run
Starting program: /home/evadeflow/projects/info4/can-daemon/_build/can-daemon --config=../scripts/handlers.lua vcan0
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
Processing messages from: vcan0 

Breakpoint 1, main (argc=3, argv=0x7fffffffdbd8) at /home/evadeflow/projects/info4/can-daemon/src/main.cpp:548
548             auto L = ::InitializeLuaInterpreter(vm, lua_can_handler_map, lua_mqtt_handler_map);
(gdb) ti
(anonymous namespace)::InitializeLuaInterpreter (vm=..., lua_can_handler_map=std::unordered_map with 0 elements, lua_mqtt_handler_map=std::unordered_map with 0 elements)
    at /home/evadeflow/projects/info4/can-daemon/src/main.cpp:469
469 {
Call took 0.0643 ms
(gdb) ti
470     L = luaL_newstate();
Call took 0.0011 ms
(gdb) ti
luaL_newstate () at /home/evadeflow/projects/info4/can-daemon/_build/lua-src/src/lauxlib.c:648                                                                                            
t648      lua_State *L = lua_newstate(l_alloc, NULL);
Call took 0.4028 ms
(gdb) ti
lua_newstate (f=0x7ffff773dbdf <l_alloc>, ud=0x0) at /home/evadeflow/projects/info4/can-daemon/_build/lua-src/src/lstate.c:147
147   void *l = (*f)(ud, NULL, 0, state_size(LG));
Call took: 0.1777 ms
(gdb) ti
l_alloc (ud=0x0, ptr=0x0, osize=0, nsize=616) at /home/evadeflow/projects/info4/can-daemon/_build/lua-src/src/lauxlib.c:630
630   if (nsize == 0) { 
Call took 0.0028 ms
(gdb) ti
635     return realloc(ptr, nsize);
Call took 0.0011 ms
(gdb)

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Answer 2

. , sysprof.

>= 3.20.