Stack information using %esp and %ebp in C++

esp_ebp_stack.cpp

#include <iostream>

unsigned int stack_zero;
unsigned int stack_last;

#define GETREG(reg, out) \                              
    asm("movl %%" #reg ", %0"\
            : "=r" (out)\ 
            : \
    )        

#define LOGESP() \   
    unsigned int __esp__; \
    unsigned int __ebp__; \
    GETREG(esp, __esp__); \
    GETREG(ebp, __ebp__); \ 
    std::cout << "%esp = " << __esp__ << "; %ebp = " << __ebp__ << std::endl; 

void subfun(int amrec) {   
    LOGESP();                   
    unsigned int stack_old = stack_last;
    std::cout << "Stack size: " << ((long)stack_zero - (long)__esp__) << "B "         << "(frame size: " << ((long)stack_last - (long)__ebp__) << "B "    
        << "[from " << stack_last << " to " << __esp__ << "])" << std::endl << std::endl;
    stack_last = __ebp__;
    if(amrec <= 0) return;
    subfun(amrec - 1);
    stack_last = stack_old;
}   

template <int M> inline size_t factorial() {
    std::cout << "[factorial<" << M << ">]: ";
    LOGESP();
    if constexpr(M == 0) return 0;
    else if constexpr(M == 1) return 1;
    else return M * factorial<M - 1>();
}   

int main() { 
    LOGESP();
    stack_zero = __ebp__;
    stack_last = __ebp__;
    std::cout << "+---" << std::endl
              << "| Calling subfun(3)" << std::endl
              << "+---" << std::endl;
                 
    subfun(3);
    stack_last = __ebp__;
    std::cout << "+---" << std::endl
              << "| Calling subfun(7)" << std::endl
              << "+---" << std::endl;
    subfun(7);
    
    std::cout << "+---" << std::endl
              << "| Calling factorial<6>()" << std::endl
              << "+---" << std::endl;
    std::cout << factorial<6>() << std::endl;                                                                                            
}    

Output with -O3 (g++)

%esp = 1189375464; %ebp = 1577812096
+---
| Calling subfun(3)
+---
%esp = 1189375400; %ebp = 1189375400
Stack size: 388436696B (frame size: 388436696B [from 1577812096 to 1189375400])

%esp = 1189375320; %ebp = 1189375320
Stack size: 388436776B (frame size: 80B [from 1189375400 to 1189375320])

%esp = 1189375240; %ebp = 1189375240
Stack size: 388436856B (frame size: 80B [from 1189375320 to 1189375240])

%esp = 1189375160; %ebp = 1189375160
Stack size: 388436936B (frame size: 80B [from 1189375240 to 1189375160])

+---
| Calling subfun(7)
+---
%esp = 1189375400; %ebp = 1189375400
Stack size: 388436696B (frame size: 388436696B [from 1577812096 to 1189375400])

%esp = 1189375320; %ebp = 1189375320
Stack size: 388436776B (frame size: 80B [from 1189375400 to 1189375320])

%esp = 1189375240; %ebp = 1189375240
Stack size: 388436856B (frame size: 80B [from 1189375320 to 1189375240])

%esp = 1189375160; %ebp = 1189375160
Stack size: 388436936B (frame size: 80B [from 1189375240 to 1189375160])

%esp = 1189375080; %ebp = 1189375080
Stack size: 388437016B (frame size: 80B [from 1189375160 to 1189375080])

%esp = 1189375000; %ebp = 1189375000
Stack size: 388437096B (frame size: 80B [from 1189375080 to 1189375000])

%esp = 1189374920; %ebp = 1189374920
Stack size: 388437176B (frame size: 80B [from 1189375000 to 1189374920])

%esp = 1189374840; %ebp = 1189374840
Stack size: 388437256B (frame size: 80B [from 1189374920 to 1189374840])

+---
| Calling factorial<6>()
+---
[factorial<6>]: %esp = 1189375400; %ebp = 1577812096
[factorial<5>]: %esp = 1189375376; %ebp = 1577812096
[factorial<4>]: %esp = 1189375376; %ebp = 1577812096
[factorial<3>]: %esp = 1189375376; %ebp = 1577812096
[factorial<2>]: %esp = 1189375376; %ebp = 1577812096
[factorial<1>]: %esp = 1189375376; %ebp = 1577812096
720