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Q240626: BUG: Extra Lines are Generated in Assembly when Using #line

Article: Q240626
Product(s): Microsoft C Compiler
Version(s): winnt:6.0
Operating System(s): 
Keyword(s): kbCodeGen kbCompiler kbDebug kbVC600bug
Last Modified: 07-MAY-2001

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft Visual C++, 32-bit Enterprise Edition, version 6.0 
- Microsoft Visual C++, 32-bit Professional Edition, version 6.0 
- Microsoft Visual C++, 32-bit Learning Edition, 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 
Technology        : kbVCsearch kbAudDeveloper kbVC600 kbVC32bitSearch
Version           : winnt:6.0
Issue type        : kbbug

=============================================================================

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