BUG: Extra Lines are Generated in Assembly when Using #line Directive

ID: Q240626

The information in this article applies to:

Microsoft Visual C++, 32-bit Editions, version 6.0

SYMPTOMS

While using #line digit-sequence "filename" with Visual C++ 6.0, extra lines may be generated in assembly code. Hence, you may need to press F10 multiple times while debugging to go to the next executable line.

CAUSE

Extra lines are generated for the #line directive.

STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article.

MORE INFORMATION

Steps to Reproduce Behavior

Compile Main.cpp:


/*******************************************
   Main.cpp file
   Uses #line directives. 
   
  ******************************************/ 

#include <stdio.h>
#line 1 "thetestfile"
void main() {
#line 1 "thetestfile"
int xx = 1;
#line 1 "thetestfile"

#line 1 "thetestfile"
if (xx == 1) {
#line 1 "thetestfile"
	printf("hello1\n");
#line 1 "thetestfile"
	++xx;
#line 1 "thetestfile"
}
#line 1 "thetestfile"


if (xx == 2) {
#line 2 "thetestfile"	
	int r = 0;
#line 2 "thetestfile"
	printf("hello2\n");
#line 2 "thetestfile"
}
#line 2 "thetestfile"

#line 3 "thetestfile"
if (xx == 2) {
#line 3 "thetestfile"	
	int r = 0;
#line 3 "thetestfile"
	printf("hello3\n");
#line 3 "thetestfile"
}
#line 3 "thetestfile"

}

Create a text file named thetestfile, and add the following lines to the file:


line 1 : Write hello1 on console
line 2 : Write hello2 on console
line 3 : Write hello3 on console

The following is the generated assembly code:


1:    line 1 : Write hello1 on console
00401010   push        ebp
00401011   mov         ebp,esp
00401013   sub         esp,4Ch
00401016   push        ebx
00401017   push        esi
00401018   push        edi
00401019   lea         edi,[ebp-4Ch]
0040101C   mov         ecx,13h
00401021   mov         eax,0CCCCCCCCh
00401026   rep stos    dword ptr [edi]
00401028   mov         dword ptr [ebp-4],1
0040102F   cmp         dword ptr [ebp-4],1
00401033   jne         main+3Bh (0040104b)
00401035   push        offset string "hello1\n" (00420034)
0040103A   call        printf (004010b0)
0040103F   add         esp,4
00401042   mov         eax,dword ptr [ebp-4]
00401045   add         eax,1
00401048   mov         dword ptr [ebp-4],eax
3:    line 3 : Write hello3 on console
0040104B   cmp         dword ptr [ebp-4],2
0040104F   jne         main+55h (00401065)
2:    line 2 : Write hello2 on console
00401051   mov         dword ptr [r],0
2:    line 2 : Write hello2 on console
00401058   push        offset string "hello2\n" (00420028)
0040105D   call        printf (004010b0)
00401062   add         esp,4
3:    line 3 : Write hello3 on console
00401065   cmp         dword ptr [ebp-4],2
00401069   jne         main+6Fh (0040107f)
3:    line 3 : Write hello3 on console
0040106B   mov         dword ptr [r],0
3:    line 3 : Write hello3 on console
00401072   push        offset string "hello3\n" (0042001c)
00401077   call        printf (004010b0)
0040107C   add         esp,4
4:
0040107F   pop         edi
00401080   pop         esi
00401081   pop         ebx
00401082   add         esp,4Ch
00401085   cmp         ebp,esp
00401087   call        __chkesp (00401130)
0040108C   mov         esp,ebp
0040108E   pop         ebp
0040108F   ret

Extra lines are generated for line 2 and line 3 directives. As a result, you need to press F10 multiple times for line 2 and line 3 while debugging.

Additional query words: #line directive extra line F10

Keywords : kbCodeGen kbCompiler kbDebug kbVC600bug
Version : winnt:6.0
Platform : winnt
Issue type : kbbug