Question

I have to write some member functions of a class in Assembly for an exam. I’ve followed every instruction but I still can’t get it to work. Here are the relevant files. The header and the main method are already provided, I just need to write the constructor and the elab1 method.

Class header

#include <iostream>
using namespace std;
struct st { int a; int vv1[4]; double vv2[4]; };
class cl 
{   double b; st s;
public:
    cl(int *p, double *d);
    void elab1(st ss);
    void stampa()
    {   int i; cout << b << ' ' << s.a << endl;
        for (i=0;i<4;i++) cout << s.vv1[i] << ' '; cout << '\t';
        for (i=0;i<4;i++) cout << s.vv2[i] << ' '; cout << endl;
        cout << endl;
    }
};

Main method for testing

// prova1.cpp
#include "cc.h" // class header
int main()
{
    st s = {1, 1,2,3,4, 1,2,3,4  };
    int v[4] = {10,11,12,13 };
    double d[4] = { 2, 3, 4, 5 };
    cl cc1(v, d);
    cc1.stampa();
    cc1.elab1(s);
    cc1.stampa();
}

And this is my assembly:

# es1.s
.text
.global __ZN2clC1EPiPe

__ZN2clC1EPiPe:

    pushl %ebp
    movl %esp, %ebp
    subl $4, %esp       

    pushl %eax
    pushl %ebx
    pushl %ecx
    pushl %edx
    pushl %esi

    cmpl $0, 12(%ebp)
    je fine
    cmpl $0, 16(%ebp)
    je fine

    movl 8(%ebp), %eax  
    movl 12(%ebp), %ebx
    movl 4(%ebx), %ecx
    movl %ecx, 12(%eax)

    fldz
    fstpl (%eax)

    movl $0, -4(%ebp)

ciclo:

    cmpl $4, -4(%ebp)
    je fine

    movl -4(%ebp), %esi     
    movl 12(%ebp), %ebx
    movl (%ebx, %esi, 4), %ecx
    subl %esi, %ecx     
    movl %ecx, 16(%eax, %esi, 4)

    movl 16(%ebp), %ebx
    pushl %eax
    movl %esi, %eax
    movl $3, %ecx
    imull %ecx
    movl %eax, %edx
    popl %eax

    movl 12(%ebp), %ecx

    fldl (%ebx, %edx, 4)
    fldl (%ecx, %esi, 4)
    faddp %st, %st(1)

    fstpl 32(%eax, %edx, 4)

    fldl (%ebx, %edx, 4)
    fldl (%eax)
    faddp %st, %st(1)

    fstpl (%eax)

    incl -4(%ebp)
    jmp ciclo

fine:

    popl %esi
    popl %edx
    popl %ecx
    popl %ebx
    popl %eax

    movl 8(%ebp), %eax

    leave
    ret

.global __ZN2cl5elab1E2st

__ZN2cl5elab1E2st: #TODO

I try to compile and link everything with the command-line statement that has been provided to us:

g++ -o es1 -fno-elide-constructors es1.s prova1.cpp

but it only gives me a bunch of undefined references:

/tmp/ccbwS0uN.o: In function `main':
prova1.cpp:(.text+0xee): undefined reference to `cl::cl(int*, double*)'
prova1.cpp:(.text+0x192): undefined reference to `cl::elab1(st)'
collect2: ld returned 1 exit status

Do you have any idea how can I solve this issue? I thought that probably I might have translated the function names in the wrong way, but I’ve checked them several times.

Answer 1

Apply c++filt to your name mangling and compare to the signature in the error message.

When removing one underscore and filtering with c++filt, I get for your mangled name cl::cl(int*, long double*) which does not match any in your error message/class declaration.

The correctly mangled name should be _ZN2clC1EPiPd for cl::cl(int*, double*).

I suggest that you improve the way (wahtever it is) to get the mangled name.