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* [Bug c/37238]  New: gcc miscompiles simple memcpy loop
@ 2008-08-25 22:07 felix-gcc at fefe dot de
  2008-08-25 22:10 ` [Bug middle-end/37238] " pinskia at gcc dot gnu dot org
  2008-08-25 22:11 ` pinskia at gcc dot gnu dot org
  0 siblings, 2 replies; 3+ messages in thread
From: felix-gcc at fefe dot de @ 2008-08-25 22:07 UTC (permalink / raw)
  To: gcc-bugs

This code:

void byte_copy(void* out, size_t len, const void* in) {
  char* s=out;
  const char* t=in;
  const char* u=t+len;
  for (;;) {
    if (t==u) break; *s=*t; ++s; ++t;
    if (t==u) break; *s=*t; ++s; ++t;
    if (t==u) break; *s=*t; ++s; ++t;
    if (t==u) break; *s=*t; ++s; ++t;
  }
}

gcc produces wrong code with -O1 or higher, but correct code with -O0.
Here is some simple test code:

#include <assert.h>
#include <string.h>

char buf[4096];
char text[128];

int main() {
  memset(buf,0,sizeof(buf));
  strcpy(text,"this is a test!\n");
  byte_copy(buf,16,text);
  assert(!memcmp(buf,"this is a test!\n\0",18));
  return 0;
}


-- 
           Summary: gcc miscompiles simple memcpy loop
           Product: gcc
           Version: 4.3.1
            Status: UNCONFIRMED
          Severity: critical
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: felix-gcc at fefe dot de
 GCC build triplet: x86_64-unknown-linux-gnu
  GCC host triplet: x86_64-unknown-linux-gnu
GCC target triplet: x86_64-unknown-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37238


^ permalink raw reply	[flat|nested] 3+ messages in thread
* [Bug middle-end/37238] gcc miscompiles simple memcpy loop
  2008-08-25 22:07 [Bug c/37238] New: gcc miscompiles simple memcpy loop felix-gcc at fefe dot de
@ 2008-08-25 22:10 ` pinskia at gcc dot gnu dot org
  2008-08-25 22:11 ` pinskia at gcc dot gnu dot org
  1 sibling, 0 replies; 3+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2008-08-25 22:10 UTC (permalink / raw)
  To: gcc-bugs



-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |pinskia at gcc dot gnu dot
                   |                            |org
           Severity|critical                    |normal
          Component|c                           |middle-end


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37238


^ permalink raw reply	[flat|nested] 3+ messages in thread
* [Bug middle-end/37238] gcc miscompiles simple memcpy loop
  2008-08-25 22:07 [Bug c/37238] New: gcc miscompiles simple memcpy loop felix-gcc at fefe dot de
  2008-08-25 22:10 ` [Bug middle-end/37238] " pinskia at gcc dot gnu dot org
@ 2008-08-25 22:11 ` pinskia at gcc dot gnu dot org
  1 sibling, 0 replies; 3+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2008-08-25 22:11 UTC (permalink / raw)
  To: gcc-bugs



------- Comment #1 from pinskia at gcc dot gnu dot org  2008-08-25 22:10 -------


*** This bug has been marked as a duplicate of 37090 ***


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |DUPLICATE


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37238


^ permalink raw reply	[flat|nested] 3+ messages in thread
end of thread, other threads:[~2008-08-25 22:11 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2008-08-25 22:07 [Bug c/37238] New: gcc miscompiles simple memcpy loop felix-gcc at fefe dot de
2008-08-25 22:10 ` [Bug middle-end/37238] " pinskia at gcc dot gnu dot org
2008-08-25 22:11 ` pinskia at gcc dot gnu dot org

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