An example shows a function definition inside another function demonstrating local scopes effect on function definition

private_definition_techdemo.c

#include <stdio.h>

static inline void call_stack() {
    void inside_block() {
        printf("inside block");
    }
    inside_block();
}

int main() {
    call_stack();
    return 0;
}

Those are other shapes of local function definitions:

#include <stdio.h>

void stack() {
    Block:{
        void inside_block() {
            printf("inside block");
        }
        inside_block();
    }
}

int main() {
    stack();
    return 0;
}

Highly discouraged.