[Devel] Major bug found: solution included!

[Martin Muskens]

Hello

I found a bug in ftcalc.c which causes in many ( if not all ) TrueType fonts
characters to display incorrect when in ftoption.h
TT_CONFIG_OPTION_BYTECODE_INTERPRETER is defined.

the original code was:

 FT_EXPORT_DEF( FT_Long )
  FT_MulDiv( FT_Long  a,
             FT_Long  b,
             FT_Long  c )
  {
    long  s;


    if ( a == 0 || b == c )
      return a;

    s  = a; a = ABS( a );
    s ^= b; b = ABS( b );
    s ^= c; c = ABS( c );

    if ( a <= 46340L && b <= 46340L && c <= 176095L && c > 0 )
    {
      a = ( a * b + ( c >> 1 ) ) / c;
    }
    else if ( c > 0 )
    {
      FT_Int64  temp, temp2;


      ft_multo64( a, b, &temp );

      temp2.hi = 0;
      temp2.lo = (FT_UInt32)(c >> 1);
      FT_Add64( &temp, &temp2, &temp );
      a = ft_div64by32( temp.hi, temp.lo, b );
    }
    else
      a = 0x7FFFFFFFL;

    return ( s < 0 ? -a : a );
  }

the change is in the line:
a = ft_div64by32( temp.hi, temp.lo, b );

the parameter b has to be changed into c, so the correct statement is:
a = ft_div64by32( temp.hi, temp.lo, C );

This bug got in somewhere around version 38.

I am looking into another bug which also resides in ftcalc.c ( when I use an
old one the bug is gone )
When I find it, I will report it!

M.Muskens
Aurelon