On 9/17/21 12:02, Martin Sebor wrote:
On 9/8/21 2:06 PM, Jason Merrill wrote:
On 9/2/21 7:53 PM, Martin Sebor wrote:
@@ -4622,28 +4622,94 @@ warn_for_null_address (location_t location,
tree op, tsubst_flags_t complain)
if (!warn_address
|| (complain & tf_warning) == 0
|| c_inhibit_evaluation_warnings != 0
- || warning_suppressed_p (op, OPT_Waddress))
+ || warning_suppressed_p (op, OPT_Waddress)
+ || processing_template_decl != 0)
Completely suppressing this warning in templates seems like a
regression; I'd think we could recognize many relevant cases before
instantiation. You just can't assume that ADDR_EXPR has the default
meaning if it has unknown type (i.e. because op0 is type-dependent).
I added the suppression to keep g++.dg/warn/pr101219.C from failing
but in hindsight I should have questioned the reasoning behind
the "no warning emitted here (no instantiation)" comment in the test.
I agree that it would be helpful to diagnose the type-independent
subset of the problem even in uninstantiated templates. Current
trunk doesn't (it never has), but with my patch and the suppression
above removed it does. I've updated the tests to expect it.
Please see the attached revision.
Martin
PS There are still more opportunities to issue -Waddress in templates
that this patch doesn't handle, e.g.,:
template <class T> bool f (T *p) { return &p == 0; }
Handling this will take more surgery.
PPS It seems that most other warnings (and even some errors, like
-Wnarrowing) are suppressed in uninstantiated templates as well,
even for non-dependent expressions. In the few test cases I looked
at Clang does better. It sounds like you'd like to see improvements
in this direction not just for -Waddress but in general. Just for
the avoidance of doubt, can you confirm that for future reference?
Yes, in general it's better to diagnose sooner.
+ if (TREE_CODE (cop) == NON_LVALUE_EXPR)
+ /* Unwrap the expression for C++ 98. */
+ cop = TREE_OPERAND (cop, 0);
What does this have to do with C++98?
+ if (TREE_CODE (cop) == PTRMEM_CST)
+ {
+ /* The address of a nonstatic data member is never null. */
+ warning_at (location, OPT_Waddress,
+ "the address %qE will never be NULL",
Capitalizing NULL when talking about pointers-to-members seems a bit
odd, but I guess it's fine.
The C++ changes are OK.
Jason
