Q62329: Internal Compiler Error ‘@(#)regMD.c:1.100’, Line 4634

Article: Q62329
Product(s): See article
Version(s): 6.00   | 6.00
Operating System(s): MS-DOS | OS/2
Keyword(s): ENDUSER | buglist6.00 | mspl13_c
Last Modified: 25-JUL-1990

The two code samples below will produce the following internal
compiler error when the code is compiled using the compact or large
memory model:

   fatal error C1001: Internal Compiler Error
   (compiler file '@(#)regMD.c:1.100', line 4634)
   Contact Microsoft Product Support Services

This error can occur with various optimizations. In general, compiling
with /Od (no optimization) or /Ox (maximum save optimization) will
work correctly. In the following examples, there are various
"failsafe" optimizations that can cause the error to go away. If one
of these optimizations is used on a compile line that would otherwise
cause the internal compiler error, the error will not appear.

 1. /** Code Sample1 **/
 2.
 3. struct str
 4. {
 5.    int *a;
 6.    int b;
 7. };
 8.
 9. void foo(struct str * w)
10. {
11.    dog( w->a[(*w).b], w->a[w->b+1] & w->a[w->b]);
12. }

In this example, using any combination that doesn't include /Oe will
result in the above error. As soon as /Oe is included, the error
doesn't occur. For example:

   cl /c /AL /Oacgilnprstwz  foo.c    << Fails with error.

   cl /c /AL /Oacgilnprstwze foo.c    << Works correctly, no error.
   cl /c /AL /Oanprswzx      foo.c    << Also works correctly.

In the second working compile line, remember that /Ox includes /Oe
(actually /Ox = /Ocegilt /Gs).

 1. /** Code Sample2 **/
 2.
 3. struct cat{
 4.    int x;
 5.    int y;
 6.    int dog[7];
 7. };
 8.
 9. void g(struct cat foo[0][1])
10. {
11.    int a=0;
12.    int b=0;
13.    unsigned int  c=0;
14.
15.    char buf[1];
16.
17.    if(0);
18.
19.    buf[0] = foo[a][b].x << 1 + foo[a][b].y;
20.    buf[0] = c + foo[a][b].x;
21. }

In the above example, using /Oe will correct the problem. However, /Ol
and /Og will also work correctly. Again, any combination of the other
optimizations will result in the above error until one of the
"failsafe" optimizations are used.

If you want to change the code in the program, the following are some
code sequences that seem to cause the error:

1. Global struct

2. Structure passed to function

3. Complex dereference of structure member

Usually, modifying the code to change this sequence will cause the
error to go away. For instance, in Example 2, any of the following
changes will eliminate the error:

1. Change dog[7] to dog [6] and declare a dummy int to pad the
   structure.

2. Change "c" from an unsigned int to int.

3. Change the order of the code or use a temporary variable in the
   assignment statement.

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