c++: failure to suppress -Wsizeof-array-div in template [PR114983]
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Commit Message
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
base-commit: 2790195500ec523cad9c7292816540e2fc19f456
Comments
On 5/9/24 12:03, Marek Polacek wrote:
> 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));
copy_warning is defined in terms of locations (as well as
TREE_NO_WARNING), so copying it before setting the location looks wrong.
> }
> 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
@@ -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);
@@ -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
new file mode 100644
@@ -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;
+}