#include "stdio.h"

template <typename t> void _swap(t& a, t& b);

int _factorial(int n)
{
    int r = 1;
    if (n <= 1) return 1;
    for (int i = 2; i <= n; i++)
    {
        r *= i;
    }
    return r;
}

int main(int argc, char** argv)
{
    int a = 4, b = 5;
    printf("org a = %d, b = %d.\n", a, b);
    _swap<int>(a, b);
    printf("now a = %d, b = %d.\n", a, b);

    printf("%d! = %d.\n", a, _factorial(a));

    return 0;
}

template <typename t> void _swap(t& a, t& b)
{
    t c = a;
    a = b;
    b = c;
    _asm
    {
        add eax, 1
        sub eax, 1
    }
    printf("finished swap.\n");

}

//----- (00401030) --------------------------------------------------------
signed int __cdecl factorial(signed int a1)
{
  signed int result; // eax@2
  signed int v2; // [sp+50h] [bp-4h]@1
  signed int v3; // [sp+4Ch] [bp-8h]@3

  v2 = 1;
  if ( a1 > 1 )
  {
    v3 = 2;
    while ( v3 <= a1 )
      v2 *= v3++;
    result = v2;
  }
  else
  {
    result = 1;
  }
  return result;
}

//----- (004010B0) --------------------------------------------------------
int __cdecl main()
{
  char v1; // [sp+Ch] [bp-48h]@1
  signed int v2; // [sp+50h] [bp-4h]@1
  signed int v3; // [sp+4Ch] [bp-8h]@1

  memset(&v1, -858993460, 0x48u);
  v2 = 4;
  v3 = 5;
  printf((int)"org a = %d, b = %d.\n", 4);
  j__swap(&v2, &v3);
  printf((int)"now a = %d, b = %d.\n", v2);
  j__factorial(v2);
  printf((int)"%d! = %d.\n", v2);
  return _chkesp(1, 0);
}

//----- (00401170) --------------------------------------------------------
int __cdecl swap(int a1, int a2)
{
  char ST04_1_0; // ST04_1@0
  int v4; // eax@1
  char v5; // [sp+Ch] [bp-44h]@1
  int v6; // [sp+4Ch] [bp-4h]@1

  memset(&v5, -858993460, 0x44u);
  v6 = *(_DWORD *)a1;
  *(_DWORD *)a1 = *(_DWORD *)a2;
  *(_DWORD *)a2 = v6;
  v4 = printf((int)"finished swap.\n", ST04_1_0);
  return _chkesp(1, v4);
}

Option Explicit

Public Function Factorial(ByVal n As Long) As Long
    Dim i As Long
    Factorial = 1
    If n < 2 Then Exit Function
    For i = 2 To n
        Factorial = Factorial * i
    Next
End Function

Public Sub Swap(ByRef a As Long, ByRef b As Long)
    Dim c As Long
    c = a
    a = b
    b = c
End Sub

Public Sub Main()
    Dim a As Long
    Dim b As Long
    a = 4
    b = 5
    Swap a, b
    MsgBox "a = " & a & ", b = " & b & "."
    MsgBox "a! = " & Factorial(a)
End Sub

.text:00401650 sub_401650      proc near               ; CODE XREF: sub_4016A0+15Cp
.text:00401650
.text:00401650 arg_0           = dword ptr  4
.text:00401650
.text:00401650                 mov     edx, [esp+arg_0]
.text:00401654                 mov     eax, 1
.text:00401659                 cmp     edx, 2
.text:0040165C                 jl      short locret_401671
.text:0040165E                 mov     ecx, 2
.text:00401663
.text:00401663 loc_401663:                             ; CODE XREF: sub_401650+1Fj
.text:00401663                 imul    eax, ecx
.text:00401666                 jo      short loc_401674
.text:00401668                 add     ecx, 1
.text:0040166B                 jo      short loc_401674
.text:0040166D                 cmp     ecx, edx
.text:0040166F                 jle     short loc_401663
.text:00401671
.text:00401671 locret_401671:                          ; CODE XREF: sub_401650+Cj
.text:00401671                 retn    4
.text:00401674 ; ---------------------------------------------------------------------------
.text:00401674
.text:00401674 loc_401674:                             ; CODE XREF: sub_401650+16j
.text:00401674                                         ; sub_401650+1Bj
.text:00401674                 call    ds:__vbaErrorOverflow
.text:0040167A                 nop
.text:0040167B                 nop
.text:0040167C                 nop
.text:0040167D                 nop
.text:0040167E                 nop
.text:0040167F                 nop
.text:0040167F sub_401650      endp

//----- (00401650) --------------------------------------------------------
#error "40167F: invalid basic block (funcsize=19)"

//----- (00401680) --------------------------------------------------------
int __stdcall sub_401680(int a1, int a2)
{
  int result; // eax@1
  int v3; // edx@1
  int v4; // ecx@1

  v3 = a2;
  result = a1;
  v4 = *(_DWORD *)a1;
  *(_DWORD *)a1 = *(_DWORD *)a2;
  *(_DWORD *)v3 = v4;
  return result;
}

//----- (004016A0) --------------------------------------------------------
int __usercall sub_4016A0<eax>(int a1<eax>)
{
  int v2; // eax@1
  int v3; // eax@1
  int v4; // eax@1
  int v5; // eax@1
  int v6; // eax@1
  int v7; // ST2C_4@1
  int v8; // eax@1
  int v9; // eax@1
  int v10; // eax@1
  int v11; // eax@1
  int v12; // eax@1
  int v13; // eax@1
  int v14; // eax@1
  int (*v15)(); // [sp+60h] [bp-Ch]@1
  int v16; // [sp+5Ch] [bp-10h]@1
  int v17; // [sp-40h] [bp-ACh]@1
  int *v18; // [sp+64h] [bp-8h]@1
  int *v19; // [sp+68h] [bp-4h]@1
  int v20; // [sp+50h] [bp-1Ch]@1
  int v21; // [sp+4Ch] [bp-20h]@1
  int v22; // [sp+48h] [bp-24h]@1
  int v23; // [sp+44h] [bp-28h]@1
  int v24; // [sp+40h] [bp-2Ch]@1
  signed int v25; // [sp+30h] [bp-3Ch]@1
  signed int v26; // [sp+20h] [bp-4Ch]@1
  signed int v27; // [sp+10h] [bp-5Ch]@1
  signed int v28; // [sp+0h] [bp-6Ch]@1
  signed int v29; // [sp+58h] [bp-14h]@1
  signed int v30; // [sp+54h] [bp-18h]@1
  signed int v31; // [sp+8h] [bp-64h]@1
  signed int v32; // [sp+18h] [bp-54h]@1
  signed int v33; // [sp+28h] [bp-44h]@1
  int v34; // [sp+38h] [bp-34h]@1

  v15 = _vbaExceptHandler;
  v16 = a1;
  v18 = &v17;
  v19 = dword_401088;
  v20 = 0;
  v21 = 0;
  v22 = 0;
  v23 = 0;
  v24 = 0;
  v25 = 0;
  v26 = 0;
  v27 = 0;
  v28 = 0;
  v29 = 4;
  v30 = 5;
  sub_401680((int)&v29, (int)&v30);
  v31 = -2147352572;
  v28 = 10;
  v32 = -2147352572;
  v27 = 10;
  v33 = -2147352572;
  v26 = 10;
  v2 = _vbaStrI4(v29);
  v3 = _vbaStrMove(&v20, v2);
  v4 = _vbaStrCat(v3, L"a = ");
  v5 = _vbaStrMove(&v21, v4);
  v6 = _vbaStrCat(L", b = ", v5);
  v7 = _vbaStrMove(&v22, v6);
  v8 = _vbaStrI4(v30);
  v9 = _vbaStrMove(&v23, v8);
  v10 = _vbaStrCat(v9, v7);
  v11 = _vbaStrMove(&v24, v10);
  v34 = _vbaStrCat(dword_40133C, v11);
  v25 = 8;
  rtcMsgBox(&v25, 0, &v26, &v27, &v28);
  _vbaFreeStrList(5, &v20, &v21, &v22, &v23, &v24);
  _vbaFreeVarList(4, &v25, &v26, &v27, &v28);
  v31 = -2147352572;
  v28 = 10;
  v32 = -2147352572;
  v27 = 10;
  v33 = -2147352572;
  v26 = 10;
  v12 = sub_401650(v29);
  v13 = _vbaStrI4(v12);
  v14 = _vbaStrMove(&v20, v13);
  v34 = _vbaStrCat(v14, L"a! = ");
  v25 = 8;
  rtcMsgBox(&v25, 0, &v26, &v27, &v28);
  _vbaFreeStr(&v20);
  return _vbaFreeVarList(4, &v25, &v26, &v27, &v28);
}