Re: [PATCH] c++: bogus -Wparentheses warning [PR112765]

[Jason Merrill]

On 11/29/23 14:42, Patrick Palka wrote:

Bootstrapped and regtested on x86_64-pc-linu-xgnu, does this look OK for
trunk?

OK.

-- >8 --

We need to consistently look through implicit INDIRECT_REF when
setting/checking for -Wparentheses warning suppression.  In passing
use STRIP_REFERENCE_REF consistently as well.

        PR c++/112765

gcc/cp/ChangeLog:

        * pt.cc (tsubst_expr) <case MODOP_EXPR>: Look through
        implicit INDIRECT_REF when propagating -Wparentheses
        warning suppression.
        * semantics.cc (maybe_warn_unparenthesized_assignment):
        Replace REFERENCE_REF_P stripping with STRIP_REFERENCE_REF.
        (finish_parenthesized_expr): Likewise.

gcc/testsuite/ChangeLog:

        * g++.dg/warn/Wparentheses-33.C: New test.
---
  gcc/cp/pt.cc                                |  2 +-
  gcc/cp/semantics.cc                         |  6 ++----
  gcc/testsuite/g++.dg/warn/Wparentheses-33.C | 24 +++++++++++++++++++++
  3 files changed, 27 insertions(+), 5 deletions(-)
  create mode 100644 gcc/testsuite/g++.dg/warn/Wparentheses-33.C

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 00b095265b6..fc4464dec02 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -20282,7 +20282,7 @@ tsubst_expr (tree t, tree args, tsubst_flags_t 
complain, tree in_decl)
           build_x_modify_expr sets it and it must not be reset
           here.  */
        if (warning_suppressed_p (t, OPT_Wparentheses))
-         suppress_warning (r, OPT_Wparentheses);
+         suppress_warning (STRIP_REFERENCE_REF (r), OPT_Wparentheses);

RETURN (r);

        }
diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index 3bf586453dc..fc00c20cba4 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -871,8 +871,7 @@ is_assignment_op_expr_p (tree t)
  void
  maybe_warn_unparenthesized_assignment (tree t, tsubst_flags_t complain)
  {
-  if (REFERENCE_REF_P (t))
-    t = TREE_OPERAND (t, 0);
+  t = STRIP_REFERENCE_REF (t);

if ((complain & tf_warning)

        && warn_parentheses
@@ -2176,8 +2175,7 @@ finish_parenthesized_expr (cp_expr expr)
      {
        /* This inhibits warnings in maybe_warn_unparenthesized_assignment
         and c_common_truthvalue_conversion.  */
-      tree inner = REFERENCE_REF_P (expr) ? TREE_OPERAND (expr, 0) : *expr;
-      suppress_warning (inner, OPT_Wparentheses);
+      suppress_warning (STRIP_REFERENCE_REF (*expr), OPT_Wparentheses);
      }

if (TREE_CODE (expr) == OFFSET_REF

diff --git a/gcc/testsuite/g++.dg/warn/Wparentheses-33.C 
b/gcc/testsuite/g++.dg/warn/Wparentheses-33.C
new file mode 100644
index 00000000000..6c65037d1b4
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wparentheses-33.C
@@ -0,0 +1,24 @@
+// PR c++/112765
+
+struct A {
+  A& operator=(const A&);
+  operator bool() const;
+};
+
+template<class T>
+void f(A a1, A a2) {
+  if ((a2 = a1)) // { dg-bogus "suggest parentheses" }
+    return;
+  bool b = (a2 = a1); // { dg-bogus "suggest parentheses" }
+}
+
+template void f<int>(A, A);
+
+template<class T>
+void g(T a1, T a2) {
+  if ((a2 = a1)) // { dg-bogus "suggest parentheses" }
+    return;
+  bool b = (a2 = a1); // { dg-bogus "suggest parentheses" }
+}
+
+template void g<A>(A, A);