Which one is faster ?

[zinc knot]

Im making my first game loop in SDL, and I want to know which is a better design choice for the update() function.

first option would be to declare last_frame_time as a global variable

uint32_t last_frame_time=0;

void update(SDL_Rect* input_rect)
{
    while (!SDL_TICKS_PASSED(SDL_GetTicks() , last_frame_time + TARGET_FRAME_TIME));
    
    last_frame_time = SDL_GetTicks();

    input_rect->x++;
    if (input_rect->y < 500)
        input_rect->y++;
}

or I could pass the last_frame_time as a parameter to update

void update(SDL_Rect* input_rect , int* last_frame_time)
{
    while (!SDL_TICKS_PASSED(SDL_GetTicks() , last_frame_time + TARGET_FRAME_TIME));
    
    *last_frame_time = SDL_GetTicks();

    input_rect->x++;
    if (input_rect->y < 500)
        input_rect->y++;
}

which way would be better in terms of speed and readability and design everything else ?

[steady shadow]

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[twilit marlin]

id advice against a global variable

you could use static int last_frame_time

also there
while (!SDL_TICKS_PASSED(SDL_GetTicks() , last_frame_time + TARGET_FRAME_TIME));
you prolly meant
while (!SDL_TICKS_PASSED(SDL_GetTicks() , *last_frame_time + TARGET_FRAME_TIME));

[zinc knot]

oh right my bad

[zinc knot]

why that ?

[twilit marlin]

it acts like a global var just the scope is limited to the function

;compile

#include <assert.h>
int fn() {
    static int i;
    return i++;
}
int main() {
    assert(fn() == 0); // default initialized to 0 like a global variable would
    assert(fn() == 1); // i was 1
    // i is now 2
}

[mortal ridge]

Compilation successful

No output.

nekrogenesis | 58ms | c | x86-64 gcc 13.2 | godbolt.org