Patch for PR analyzer/98797

[brian.sobulefsky]

Hi David,

Please find my revised patch attached. You should find all items addressed. I
have bootstrapped and rerun the testsuite (gcc and g++ only).  Also, you
should have seen my legal paperwork go in.

1) The commit message has been updated to reflect the nomenclature in the
testsuite, as well as include the required parentheses.

2) The commit message has been updated to reflect the other changes you
requested below.

3) My macros and inline code for "bit_byte_conversion" have been replaced with
the subroutine you requested. It works by modulo and division rather than
bitwise-and and bitshift, as requested. Without any specific instructions, I
put the routine in analyzer.cc and the prototype in analyzer.h, as it provides
a generic helper service. You can move it anywhere else you might want it.

4) I added the check for the field to be sizeof (char). This is actually a
cause to reject getting a char from a string constant for any case, so I
added the check near the outside of the nested ifs. Also, as a side note,
it looks to me like your example:

void test_4 ()
{
  const char *s = "ABCD";
  __analyzer_eval (*(short *)s == 'A');
}

is unrelated to my patch, as I remember a char pointer to a string constant is
handled as a special case elsewhere and does not end up in
maybe_fold_sub_svalue.

5) I updated the modification to get_offset_region so that my new code is only
run in the case of a zerop. This was really the failure issue anyway. I still
have it building a new constant svalue of zero, because I do not know for sure
if the zero pointer type tree and zero integer type tree are different enough to
cause confusion down the line when getting the character.

6) My new subroutine get_parent_cast_region takes any svalues as an argument
and does its own checks for svalue_kind correctness, returning NULL otherwise.
My reason for this is so get_binding_recursive would remain absolutely clean,
the way its recursive call is. Basically, get_binding_recursive can just call
get_parent_cast_region as an assignment within a conditional, just like
the recursion step is, and the returned NULLs, whether by incorrect type or by
not finding a binding for the correct type, causes it to bypass returning there.

7) The if guards were updated as requested.

8) I used your get_field_at_bit_offset routine as requested. To stress again,
this was a static function to region.cc. I had to add a forward declaration
(I again used analyzer.h because it is a "generic helper" function, but that
is easy for you to change if you do not like it there) *and* I had to update
your definition to extern rather than static. Otherwise, it seems to work.

9) The compound conditionals should all be to your liking now.

10) After all the back and forth, I think I am using "approved" helper
functions and macros rather than accessing the tree fields directly. It seems
they all work correctly.

11) All preexisting deja-gnu tests are on the original lines they were on
before. All new tests are appended. Blank lines are left where the dg-bogus
calls were.


Thank you,
Brian
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