C++ PATCH to prevent bogus -Wint-in-bool-context warning (PR c++/79184)

C++ PATCH to prevent bogus -Wint-in-bool-context warning (PR c++/79184)

[Marek Polacek]

This PR complains about -Wint-in-bool-context warning where it shouldn't.
Here, in "f<1 * 1>()" the MULT_EXPR isn't really in a boolean context, but we
warn anyway during overload resolution, when adding various template
candidates.  I believe the way to prevent this is to honor complain &
tf_warning which is what this patch does.  Does that seem reasonable or
is there a better way?

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

2017-02-10  Marek Polacek  <polacek@redhat.com>

	PR c++/79184
	* cvt.c (ocp_convert): Add a sentinel against -Wint-in-bool-context
	if warnings shouldn't be given.

	* g++.dg/warn/Wint-in-bool-context-1.C: New.

diff --git gcc/cp/cvt.c gcc/cp/cvt.c
index ae9991a..5f4b5e3 100644
--- gcc/cp/cvt.c
+++ gcc/cp/cvt.c
@@ -798,7 +798,15 @@ ocp_convert (tree type, tree expr, int convtype, int flags,
 	     to the underlying type first.  */
 	  if (SCOPED_ENUM_P (intype) && (convtype & CONV_STATIC))
 	    e = build_nop (ENUM_UNDERLYING_TYPE (intype), e);
-	  return cp_truthvalue_conversion (e);
+	  if (complain & tf_warning)
+	    return cp_truthvalue_conversion (e);
+	  else
+	    {
+	      /* Prevent bogus -Wint-in-bool-context warnings coming
+		 from c_common_truthvalue_conversion down the line.  */
+	      warning_sentinel w (warn_int_in_bool_context);
+	      return cp_truthvalue_conversion (e);
+	    }
 	}
 
       converted = convert_to_integer_maybe_fold (type, e, dofold);
diff --git gcc/testsuite/g++.dg/warn/Wint-in-bool-context-1.C gcc/testsuite/g++.dg/warn/Wint-in-bool-context-1.C
index e69de29..117eca4 100644
--- gcc/testsuite/g++.dg/warn/Wint-in-bool-context-1.C
+++ gcc/testsuite/g++.dg/warn/Wint-in-bool-context-1.C
@@ -0,0 +1,16 @@
+// PR c++/79184
+// { dg-do compile }
+// { dg-options "-Wint-in-bool-context" }
+
+enum { E = 2 };
+template <bool> void f(int) { }
+template <int> void f() {}
+
+int
+main ()
+{
+  f<1 * 1>(); // { dg-bogus "in boolean context" }
+  f<1 << 1>(); // { dg-bogus "in boolean context" }
+  f<1 ? 3 : 2>(); // { dg-bogus "in boolean context" }
+  f<E>(); // { dg-bogus "in boolean context" }
+}

	Marek

Re: C++ PATCH to prevent bogus -Wint-in-bool-context warning (PR c++/79184)

[Jason Merrill]

OK.

On Fri, Feb 10, 2017 at 10:55 AM, Marek Polacek <polacek@redhat.com> wrote:
> This PR complains about -Wint-in-bool-context warning where it shouldn't.
> Here, in "f<1 * 1>()" the MULT_EXPR isn't really in a boolean context, but we
> warn anyway during overload resolution, when adding various template
> candidates.  I believe the way to prevent this is to honor complain &
> tf_warning which is what this patch does.  Does that seem reasonable or
> is there a better way?
>
> Bootstrapped/regtested on x86_64-linux, ok for trunk?
>
> 2017-02-10  Marek Polacek  <polacek@redhat.com>
>
>         PR c++/79184
>         * cvt.c (ocp_convert): Add a sentinel against -Wint-in-bool-context
>         if warnings shouldn't be given.
>
>         * g++.dg/warn/Wint-in-bool-context-1.C: New.
>
> diff --git gcc/cp/cvt.c gcc/cp/cvt.c
> index ae9991a..5f4b5e3 100644
> --- gcc/cp/cvt.c
> +++ gcc/cp/cvt.c
> @@ -798,7 +798,15 @@ ocp_convert (tree type, tree expr, int convtype, int flags,
>              to the underlying type first.  */
>           if (SCOPED_ENUM_P (intype) && (convtype & CONV_STATIC))
>             e = build_nop (ENUM_UNDERLYING_TYPE (intype), e);
> -         return cp_truthvalue_conversion (e);
> +         if (complain & tf_warning)
> +           return cp_truthvalue_conversion (e);
> +         else
> +           {
> +             /* Prevent bogus -Wint-in-bool-context warnings coming
> +                from c_common_truthvalue_conversion down the line.  */
> +             warning_sentinel w (warn_int_in_bool_context);
> +             return cp_truthvalue_conversion (e);
> +           }
>         }
>
>        converted = convert_to_integer_maybe_fold (type, e, dofold);
> diff --git gcc/testsuite/g++.dg/warn/Wint-in-bool-context-1.C gcc/testsuite/g++.dg/warn/Wint-in-bool-context-1.C
> index e69de29..117eca4 100644
> --- gcc/testsuite/g++.dg/warn/Wint-in-bool-context-1.C
> +++ gcc/testsuite/g++.dg/warn/Wint-in-bool-context-1.C
> @@ -0,0 +1,16 @@
> +// PR c++/79184
> +// { dg-do compile }
> +// { dg-options "-Wint-in-bool-context" }
> +
> +enum { E = 2 };
> +template <bool> void f(int) { }
> +template <int> void f() {}
> +
> +int
> +main ()
> +{
> +  f<1 * 1>(); // { dg-bogus "in boolean context" }
> +  f<1 << 1>(); // { dg-bogus "in boolean context" }
> +  f<1 ? 3 : 2>(); // { dg-bogus "in boolean context" }
> +  f<E>(); // { dg-bogus "in boolean context" }
> +}
>
>         Marek