Small compiler bug signed vs. unsigned char !

[Ingo Krabbe]

hi,

I tried to compile the libz.so.1.0.4 from redhat archive (zlib...src.rpm)

The test program made an error with egcs, while it doesn't it with gcc2.7.2.2

The problem was the if--else construction:

  while (n && m < 4)
  {
        printf("   %d   %d  \n", (int)*p, m);
    if (*p == (Byte)(m < 2 ? 0 : 0xff))  /* Here is the conversion problem ! */
      m++;
    else if (*p)
      m = 0;
    else
      m = 4 - m;
    p++, n--;
  }

The error is reproducable ! when compiling this code with p={0,0,255,255,255...}
you get the wrong output:
   0   0  
   0   1  
   255   2  
   255   0  
   255   0  
   255   0  
   255   0  
 ...

without the (Byte) conversion (which is actually a unsigned char) you get
   0   0  
   0   1  
   255   2  
   255   3  

I encountered a similar error with CC on a Sun Solaris 2.xx :-)
Maybe its correct what you made with your compiler. But this behaviour is not
very nice especially because there is no *Warning* !

CU INGO