[PATCH PR c++/17132] Add new argument NOSIDE to find_overload_match

[Siva Chandra <sivachandra at google dot com>]

The bug with examples where it manifests is detailed on the bug page.
To summarize here:

When expressions involving calls to virtual methods are evaluated
under EVAL_AVOID_SIDE_EFFECTS, the intermediate objects could be
zeroed values. In which case, when find_overload_match tries to
(indirectly) lookup the method for the most derived type of the object
via its vptr, GDB trips with "Cannot access memory at address 0x0."
This patch adds an additional argument NOSIDE to find_overload_match
which serves as a flag to indicate whether method resolution should be
performed by looking up the most derived object via the vptr. When
NOSIDE is EVAL_AVOID_SIDE_EFFECTS, the method for the compile time
type (instead of the most derived type) of the object is returned by
find_overload_match. This will not affect the functionality as all
that is important when evaluating under EVAL_AVOID_SIDE_EFFECTS is the
return type of the method.

Regression tested testsuite/gdb.cp. But, am I simplifying the problem somewhere?

ChangeLog
2014-07-09  Siva Chandra Reddy  <sivachandra@google.com>

    gdb/

            * eval.c: Update all calls to find_overload_match.
            * valarith.c: Update calls to find_overload_match.
            (value_user_defined_cpp_op, value_user_defined_op): New
            argument NOSIDE. Update all callers.
            * valops.c (find_overload_match): New argument NOSIDE.
            * value.h (find_overload_match): Update signature.

    gdb/testsuite

            * gdb.cp/pr17132.cc: New file.
            * gdb.cp/pr17132.exp: New file.

Attachment: fix_pr17132_v1.txt
Description: Text document