[Bug middle-end/37861] New: Bogus array bounds warning

["rguenth at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org>]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain, Size: 1609 bytes --]

extern int printf (__const char *__restrict __format, ...);

  static int f2(char formatstr[10][100]) {
    int anz;
    for( anz = 0; anz < 10; ++anz ) {
      printf( "%d %s\n", anz, formatstr[anz] );
    } 
    return anz;
  }


  static   char formatstr[10][100];
  int main( void ) {
    int anz;
    anz = f2(formatstr);
    printf( "   %d\n",anz);
    return 0;
  }


with -O3 -Wall this reports

t.c: In function ‘main’:
t.c:6: warning: array subscript is above array bounds
t.c:6: warning: array subscript is above array bounds
t.c:6: warning: array subscript is above array bounds
t.c:6: warning: array subscript is above array bounds
t.c:6: warning: array subscript is above array bounds
t.c:6: warning: array subscript is above array bounds
t.c:6: warning: array subscript is above array bounds
t.c:6: warning: array subscript is above array bounds

because we end up with

<bb 3>:
  # anz_23 = PHI <anz_6(4), anz_22(6)>
  D.1572_5 = (long unsigned int) anz_23;
  D.1573_7 = D.1572_5 * 100;
  D.1574_8 = &formatstr[0][D.1573_7];
  printf (&"%d %s\n"[0], anz_23, D.1574_8);
  anz_9 = anz_23 + 1;

<bb 4>:
  # anz_6 = PHI <anz_9(3)>
  if (anz_6 <= 9)
    goto <bb 3>;
  else
    goto <bb 5>;


-- 
           Summary: Bogus array bounds warning
           Product: gcc
           Version: 4.3.2
            Status: UNCONFIRMED
          Keywords: diagnostic
          Severity: normal
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: rguenth at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37861