[Bug optimization/13609] New: sscanf optimization error

[Bug optimization/13609] New: sscanf optimization error

[BStrauss-gcc at feliscatus dot org]

Different results for small test program when compiled -O2 vs no optimization 
(non-optimized version is right):

#define cNV2N(a, b) printf("-> %10u expected %10u\n", 
convertNtopVersionToNumber(a), b)

unsigned int convertNtopVersionToNumber(char *versionString) {
  /* This one is purely an arbitrary conversion.
   *
   * But it knows about the version # schemes we've used in the past
   *  e.g. 2.2c, 2.2.50, 2.2.97, 3.0pre1, 3.0rc1 etc. so that the number truly 
is relative
   * for numeric testing.
   *
   *  The goal is to get the following converted to ascending numeric order:
   *
   *   1.3 2.1 2.1.2 2.1.3 2.1.50 2.1.90 2.2 2.2a 2.2b 2.2c 2.2.50 2.2.97 
3.0pre1 3.0rc1 3.0
   *
   * e.g.:
   *
   *   1.3     103000000
   *   2.1     201000000
   *   2.1.1   201000001
   *   2.1.2   201000002
   *   2.1.3   201000003
   *   2.1.50  201050000
   *   2.1.90  201090000
   *   2.2     202000000
   *   2.2a    202000100
   *   2.2b    202000200
   *   2.2c    202000300
   *   2.2.50  202050000
   *   2.2.90  202090000
   *   3.0pre1 299998001
   *   3.0rc1  299999001
   *   3.0rc2  299999002
   *   3.0     300000000
   *
   * n.m   -> nmm000000
   * n.m.x -> nmmyyy0xx  (if x>=50 yyy=x else xx=x)
   * n.ml  -> nmm000l00 (where a=1, b=2, etc.)
   */
  unsigned int f, n=0, m=0, x=0, y=0, c=0, prerc=0;
  unsigned char l=0;

  if (versionString == 0) {
    return 999999999;
  }

  printf("'%10s'", versionString);

  f = sscanf(versionString, "%u.%upre%u", &n, &m, &x);
  if(f>=3) {
    prerc=2;
  } else {
    f = sscanf(versionString, "%u.%urc%u", &n, &m, &x);
    if(f>=3) {
      prerc=1;
    } else {
      f = sscanf(versionString, "%u.%u%[a-z].%u", &n, &m, &l, &x);
      if(f>=3) {
        if(l>0)
          l = tolower(l) - 'a' + 1;
      } else {
        l = 0;
        f = sscanf(versionString, "%u.%u.%u", &n, &m, &x);
        if (f<=0) {
          return 999999999;
        }
      }
    }
  }
  if (x>=50) {
    y=x;
    x=0;
  }
  printf("\tis n%u m%u y%u l%u x%u prerc%u f=%u\t", n, m, y, l, x, prerc, f);
  return n*100000000 + m*1000000 + y*1000 + l*100 + x - 1000*prerc;
}

int main(int argc, char *argv[]) {
    cNV2N("2.2",    202000000);
    cNV2N("2.2c",   202000300);
    cNV2N("2.2c.1", 202000301);
}


$ gcc sscanftest.c -o sscanftest
$ ./sscanftest 
'       2.2'    is n2 m2 y0 l0 x0 prerc0 f=2    ->  202000000 expected  
202000000
'      2.2c'    is n2 m2 y0 l3 x0 prerc0 f=3    ->  202000300 expected  
202000300
'    2.2c.1'    is n2 m2 y0 l3 x1 prerc0 f=4    ->  202000301 expected  
202000301

$ gcc -O2 sscanftest.c -o sscanftest
$ ./sscanftest 
'       2.2'    is n2 m2 y0 l0 x0 prerc0 f=2    ->  202000000 expected  
202000000
'      2.2c'    is n0 m2 y0 l3 x0 prerc0 f=3    ->    2000300 expected  
202000300
'    2.2c.1'    is n0 m2 y0 l3 x1 prerc0 f=4    ->    2000301 expected  
202000301


$ gcc --version
gcc (GCC) 3.2.2 20030222 (Red Hat Linux 3.2.2-5)

-- 
           Summary: sscanf optimization error
           Product: gcc
           Version: 3.2.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: BStrauss-gcc at feliscatus dot org
                CC: gcc-bugs at gcc dot gnu dot org
  GCC host triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13609

[Bug optimization/13609] sscanf optimization error

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-01-07 22:25 -------
Not a bug %[a-z] expects a char array and you are only supplying it with enough room for zero 
characters.

>From the man of printf:
       [      Matches a nonempty sequence of characters from the specified set of accepted 
characters; the next pointer must be  a  pointer
              to  char,  and  there  must be enough room for all the characters in the string, plus a 
terminating NUL character.  The usual
              skip of leading white space is suppressed.  The string is to be made up of characters in 
(or not in) a  particular  set;  the
              set  is  defined  by  the  characters between the open bracket [ character and a close 
bracket ] character.  The set excludes
              those characters if the first character after the open bracket is a circumflex ^.  To include 
a close  bracket  in  the  set,
              make  it the first character after the open bracket or the circumflex; any other position 
will end the set.  The hyphen char-
              acter - is also special; when placed between two other characters, it adds all intervening 
characters to the set.  To include
              a  hyphen,  make  it  the  last character before the final close bracket.  For instance, 
`[^]0-9-]' means the set `everything
              except close bracket, zero through nine, and hyphen'.  The string ends with the 
appearance of a character  not  in  the  (or,
              with a circumflex, in) set or when the field width runs out.

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13609