From: Marek Polacek <polacek@redhat.com>
Date: Wed, 8 May 2024 21:02:49 +0000 (-0400)
Subject: c++: failure to suppress -Wsizeof-array-div in template [PR114983]
X-Git-Tag: basepoints/gcc-16~9202
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=646db3d30bd071a1b671b4f91c9ea2ab7f2be21c;p=thirdparty%2Fgcc.git

c++: failure to suppress -Wsizeof-array-div in template [PR114983]

-Wsizeof-array-div offers a way to suppress the warning by wrapping
the second operand of the division in parens:

  sizeof (samplesBuffer) / (sizeof(unsigned char))

but this doesn't work in a template, because we fail to propagate
the suppression bits.  Do it, then.

The finish_parenthesized_expr hunk is not needed because suppress_warning
isn't very fine-grained.  But I think it makes sense to be explicit and
not rely on OPT_Wparentheses also suppressing OPT_Wsizeof_array_div.

	PR c++/114983

gcc/cp/ChangeLog:

	* pt.cc (tsubst_expr) <case SIZEOF_EXPR>: Use copy_warning.
	* semantics.cc (finish_parenthesized_expr): Also suppress
	-Wsizeof-array-div.

gcc/testsuite/ChangeLog:

	* g++.dg/warn/Wsizeof-array-div3.C: New test.
---

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 8787eabb9fd..a7d9fcf930e 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -20570,6 +20570,7 @@ tsubst_expr (tree t, tree args, tsubst_flags_t complain, tree in_decl)
 		TREE_READONLY (r) = 1;
 	      }
 	    SET_EXPR_LOCATION (r, EXPR_LOCATION (t));
+	    copy_warning (r, t);
 	  }
 	RETURN (r);
       }
diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index b8c2bf8771f..71520dcd4fa 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -2306,6 +2306,8 @@ finish_parenthesized_expr (cp_expr expr)
       /* This inhibits warnings in maybe_warn_unparenthesized_assignment
 	 and c_common_truthvalue_conversion.  */
       suppress_warning (STRIP_REFERENCE_REF (*expr), OPT_Wparentheses);
+      /* And maybe_warn_sizeof_array_div.  */
+      suppress_warning (STRIP_REFERENCE_REF (*expr), OPT_Wsizeof_array_div);
     }
 
   if (TREE_CODE (expr) == OFFSET_REF
diff --git a/gcc/testsuite/g++.dg/warn/Wsizeof-array-div3.C b/gcc/testsuite/g++.dg/warn/Wsizeof-array-div3.C
new file mode 100644
index 00000000000..bfd690325e5
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wsizeof-array-div3.C
@@ -0,0 +1,27 @@
+// PR c++/114983
+// { dg-do compile { target c++11 } }
+// { dg-options "-Wsizeof-array-div" }
+
+using size_t = decltype (sizeof (0));
+unsigned int samplesBuffer[40];
+
+template <typename T>
+constexpr inline size_t fn1()
+{
+  return ((sizeof(samplesBuffer)) / (sizeof(T))); // { dg-bogus "expression does not compute" }
+}
+
+template <typename T>
+constexpr inline size_t fn2()
+{
+  return ((sizeof(samplesBuffer)) / sizeof(T)); // { dg-warning "expression does not compute" }
+}
+
+size_t
+g ()
+{
+  auto sz = sizeof (samplesBuffer) / (sizeof(unsigned char));
+  sz += fn1<unsigned char>();
+  sz += fn2<unsigned char>(); // { dg-message "required from here" }
+  return sz;
+}