DOCUMENT:Q240626  07-MAY-2001  [visualc]
TITLE   :BUG: Extra Lines are Generated in Assembly when Using #line
PRODUCT :Microsoft C Compiler
PROD/VER:winnt:6.0
OPER/SYS:
KEYWORDS:kbCodeGen kbCompiler kbDebug kbVC600bug

======================================================================
-------------------------------------------------------------------------------
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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