On 8/29/24 12:23 PM, Marek Polacek wrote:
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk/14?
-- >8 --
Pre r14-4793, we'd call warn_tautological_cmp -> operand_equal_p
with operands wrapped in NON_DEPENDENT_EXPR, which works, since
o_e_p bails for codes it doesn't know. But now we pass operands
not encapsulated in NON_DEPENDENT_EXPR, and crash, because the
template tree for &a[x] has null DECL_FIELD_OFFSET.
Why are we trying to compare DECL_FIELD_OFFSET in C++, anyway? I'd
think we should limit that to C and in C++ rely on FIELD_DECL identity.
I don't think I meant this warning to be called in a template,
so let's avoid the problem this easy way.
Hmm, it seems potentially useful in a template, especially since we
suppress it in instantiations.
PR c++/116534
gcc/cp/ChangeLog:
* call.cc (build_new_op) <case NE_EXPR>: Don't call
warn_tautological_cmp in a template.
gcc/testsuite/ChangeLog:
* g++.dg/warn/Wtautological-compare4.C: New test.
---
gcc/cp/call.cc | 4 +++-
.../g++.dg/warn/Wtautological-compare4.C | 21 +++++++++++++++++++
2 files changed, 24 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/warn/Wtautological-compare4.C
diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc
index fa7f05d76f6..d0d0c4b4d3c 100644
--- a/gcc/cp/call.cc
+++ b/gcc/cp/call.cc
@@ -7526,7 +7526,9 @@ build_new_op (const op_location_t &loc, enum tree_code
code, int flags,
&& ((code_orig_arg1 == BOOLEAN_TYPE)
^ (code_orig_arg2 == BOOLEAN_TYPE)))
maybe_warn_bool_compare (loc, code, arg1, arg2);
- if (complain & tf_warning && warn_tautological_compare)
+ if ((complain & tf_warning)
+ && warn_tautological_compare
+ && !processing_template_decl)
warn_tautological_cmp (loc, code, arg1, arg2);
/* Fall through. */
case SPACESHIP_EXPR:
diff --git a/gcc/testsuite/g++.dg/warn/Wtautological-compare4.C
b/gcc/testsuite/g++.dg/warn/Wtautological-compare4.C
new file mode 100644
index 00000000000..96308f49a42
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wtautological-compare4.C
@@ -0,0 +1,21 @@
+// PR c++/116534
+// { dg-do compile }
+// { dg-options "-Wall" }
+
+template <class A>
+struct Test {
+ bool foo(unsigned x, unsigned y) {
+ bool test = &a[x] == &b[y];
+ return test;
+ }
+ unsigned *a;
+ unsigned *b;
+};
+
+void
+g ()
+{
+ Test<int> t;
+ t.foo (0u, 1u);
+ t.foo (0u, 0u);
+}
base-commit: cdd5dd2125ca850aa8599f76bed02509590541ef
