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

[Marek Polacek]

Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?

-- >8 --
-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.
---
 gcc/cp/pt.cc                                  |  1 +
 gcc/cp/semantics.cc                           |  2 ++
 .../g++.dg/warn/Wsizeof-array-div3.C          | 27 +++++++++++++++++++
 3 files changed, 30 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/warn/Wsizeof-array-div3.C

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 8787eabb9fd..46cf8a737fb 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -20569,6 +20569,7 @@ tsubst_expr (tree t, tree args, tsubst_flags_t 
complain, tree in_decl)
                TREE_SIDE_EFFECTS (r) = 0;
                TREE_READONLY (r) = 1;
              }
+           copy_warning (r, t);
            SET_EXPR_LOCATION (r, EXPR_LOCATION (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;
+}

base-commit: 2790195500ec523cad9c7292816540e2fc19f456
-- 
2.45.0