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From: hkr@mcshh.hanse.de (Holger Kruse)
Newsgroups: comp.sys.amiga.programmer
Subject: Bug in SAS C 5.10a ?
Keywords: SAS C,C,Bug
Message-ID: <9195@mcshh.hanse.de>
Date: 19 May 91 05:17:53 GMT
Article-I.D.: mcshh.9195
Distribution: comp
Lines: 62


I think I found a serious bug in SAS C 5.10a and some earlier versions.
I reported the bug to SAS a month ago but have not got any answer yet.

According to the manual, the size of a single subscript of an array may be
larger than 32767 if long (32-bit) integers are used, this means that a 
declaration like
  int far a[2][40000];
is valid, if long integers are used.

The compiler produces incorrect code, if the size of the second subscript
is larger than 32767 and if the first subscript is indexed by a variable
less than 32 bits long.

Example:
  char far a[3][34000];
  main()
  {
    short c=2;  /*or: char c=2; */
    a[c][0]=0;
  }

After compiling ("LC filename") "OMD" produces the following
disassembly:

  ...
 | 0002  7E02               MOVEQ     #02,D7
 | 0004  2007               MOVE.L    D7,D0           \ this calculates a
 | 0006  C1FC 84D0          MULS.W    #84D0,D0        / NEGATIVE offset !!!
 | 000A  41F9  0000 0000-01 LEA       01.00000000,A0
 | 0010  D1C0               ADDA.L    D0,A0
 | 0012  4210               CLR.B     (A0)            
  ...

Changing the assignment "a[c][0]=0" to "a[(long)c][0]=0" leads
to a correct compilation result:
  ...
 | 0002  7E02               MOVEQ     #02,D7
 | 0004  2007               MOVE.L    D7,D0           \ 
 | 0006  48C0               EXT.L     D0               \ this is OK
 | 0008  223C 0000 84D0     MOVE.L    #000084D0,D1     /
 | 000E  4EBA  0000-XX.1    JSR       __CXM33(PC)     /
 | 0012  41F9  0000 0000-01 LEA       01.00000000,A0
 | 0018  D1C0               ADDA.L    D0,A0
 | 001A  4210               CLR.B     (A0)
  ...

I could understand if SAS C reported an error in the above
case, but there is no error message or warning. You simply get a GURU
when you run the compiled program.

Or maybe I am wrong and what I am doing is illegal in C ?

Btw, the Unix TeX package contains lots of declarations like the above.
So if you try to compile it on an Amiga, better be careful...

Holger Kruse

-------------------------------------+----------------------------------
Holger Kruse                         ! German BTX:     040526128800-0001 
Zwijndrechtring 50, 2000 Norderstedt ! INTERNET:      hkr@mcshh.hanse.de
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