diff mbox series

c++: Fix bogus -Wparentheses warning with fold-expression [PR94505]

Message ID 20200419165939.2539043-1-polacek@redhat.com
State New
Headers show
Series c++: Fix bogus -Wparentheses warning with fold-expression [PR94505] | expand

Commit Message

Marek Polacek April 19, 2020, 4:59 p.m. UTC 
We issue bogus -Wparentheses warnings (3 of them!) for this fold expression:

  ((B && true) || ...)

Firstly, issuing a warning for a compiler-generated expression is wrong
and secondly, B && true must be wrapped in ( ) otherwise you'll get
error: binary expression in operand of fold-expression.

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

	PR c++/94505 - bogus -Wparentheses warning with fold-expression.
	* pt.c (fold_expression): Add warning_sentinel for -Wparentheses
	before calling build_x_binary_op.

	* g++.dg/cpp1z/fold11.C: New test.
---
 gcc/cp/pt.c                         |  1 +
 gcc/testsuite/g++.dg/cpp1z/fold11.C | 12 ++++++++++++
 2 files changed, 13 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/cpp1z/fold11.C


base-commit: fc186077486fb6e5453157ad8507c66d0a34017c

Comments

Jason Merrill April 20, 2020, 7:32 p.m. UTC | #1 
On 4/19/20 12:59 PM, Marek Polacek wrote:
> We issue bogus -Wparentheses warnings (3 of them!) for this fold expression:
> 
>    ((B && true) || ...)
> 
> Firstly, issuing a warning for a compiler-generated expression is wrong
> and secondly, B && true must be wrapped in ( ) otherwise you'll get
> error: binary expression in operand of fold-expression.
> 
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?

OK.

> 	PR c++/94505 - bogus -Wparentheses warning with fold-expression.
> 	* pt.c (fold_expression): Add warning_sentinel for -Wparentheses
> 	before calling build_x_binary_op.
> 
> 	* g++.dg/cpp1z/fold11.C: New test.
> ---
>   gcc/cp/pt.c                         |  1 +
>   gcc/testsuite/g++.dg/cpp1z/fold11.C | 12 ++++++++++++
>   2 files changed, 13 insertions(+)
>   create mode 100644 gcc/testsuite/g++.dg/cpp1z/fold11.C
> 
> diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
> index 9e39f46a090..5d5941eddb7 100644
> --- a/gcc/cp/pt.c
> +++ b/gcc/cp/pt.c
> @@ -12356,6 +12356,7 @@ fold_expression (tree t, tree left, tree right, tsubst_flags_t complain)
>     if (FOLD_EXPR_MODIFY_P (t))
>       return build_x_modify_expr (input_location, left, code, right, complain);
>   
> +  warning_sentinel s(warn_parentheses);
>     switch (code)
>       {
>       case COMPOUND_EXPR:
> diff --git a/gcc/testsuite/g++.dg/cpp1z/fold11.C b/gcc/testsuite/g++.dg/cpp1z/fold11.C
> new file mode 100644
> index 00000000000..09a30555eee
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp1z/fold11.C
> @@ -0,0 +1,12 @@
> +// PR c++/94505 - bogus -Wparentheses warning with fold-expression.
> +// { dg-do compile { target c++17 } }
> +// { dg-options "-Wparentheses" }
> +
> +template <bool... B>
> +bool foo () {
> +    return ((B && true) || ...); // { dg-bogus "suggest parentheses" }
> +}
> +
> +int main () {
> +    foo<true, false, false, true> ();
> +}
> 
> base-commit: fc186077486fb6e5453157ad8507c66d0a34017c
>
diff mbox series

Patch

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 9e39f46a090..5d5941eddb7 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -12356,6 +12356,7 @@  fold_expression (tree t, tree left, tree right, tsubst_flags_t complain)
   if (FOLD_EXPR_MODIFY_P (t))
     return build_x_modify_expr (input_location, left, code, right, complain);
 
+  warning_sentinel s(warn_parentheses);
   switch (code)
     {
     case COMPOUND_EXPR:
diff --git a/gcc/testsuite/g++.dg/cpp1z/fold11.C b/gcc/testsuite/g++.dg/cpp1z/fold11.C
new file mode 100644
index 00000000000..09a30555eee
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/fold11.C
@@ -0,0 +1,12 @@ 
+// PR c++/94505 - bogus -Wparentheses warning with fold-expression.
+// { dg-do compile { target c++17 } }
+// { dg-options "-Wparentheses" }
+
+template <bool... B>
+bool foo () {
+    return ((B && true) || ...); // { dg-bogus "suggest parentheses" }
+}
+
+int main () {
+    foo<true, false, false, true> ();
+}