[PATCH v2] c++: Don't quote nothrow in diagnostic

[Marek Polacek <polacek@redhat.com>]

On Mon, Sep 26, 2022 at 12:34:04PM -0400, Jason Merrill wrote:
> On 9/26/22 03:50, Richard Biener wrote:
> > On Fri, Sep 23, 2022 at 8:41 PM Marek Polacek via Gcc-patches
> > <gcc-patches@gcc.gnu.org> wrote:
> > > 
> > > In <https://gcc.gnu.org/pipermail/gcc-patches/2022-September/602057.html>
> > > Jason noticed that we quote "nothrow" in diagnostics even though it's
> > > not a keyword in C++.  Just removing the quotes didn't work because
> > > then -Wformat-diag complains, so this patch replaces it with "no-throw".
> > > 
> > > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
> > 
> > That doesn't look like an improvement to me.  Can we quote 'nothrow()' instead?

Understood.
 
> nothrow() is a syntax error; the C++11 keyword is 'noexcept'. std::nothrow
> is a dummy placement argument used to indicate that a new-expression should
> return null rather than throw on failure.
> 
> But bizarrely, the library traits use the word "nothrow".  Marek's patch
> clarifies that we are not trying to refer to anything in the language.
> 
> > I'd rather leave it alone than changing it to no-throw.  Why does -Wformat-diag
> > complain?  If we shouldn't quote nothrow that should be adjusted?
> 
> I think -Wformat-diag complains because "nothrow" is an attribute; it also
> includes some other attribute names in the list of "keywords".
> 
> I would also be fine with just removing the quotes and removing nothrow from
> c_keywords.

Like below?   Bootstrapped/regtested on x86_64-pc-linux-gnu.

Note that now I see warnings with my system compiler (gcc-12.2.1).  Can
I commit the c-format.cc hunk to gcc 12 so that eventually even gcc 12
stops warning?

-- >8 --
In <https://gcc.gnu.org/pipermail/gcc-patches/2022-September/602057.html>
Jason noticed that we quote "nothrow" in diagnostics even though it's
not a keyword in C++.  This patch removes the quotes and also drops
"nothrow" from c_keywords.

gcc/c-family/ChangeLog:

	* c-format.cc (c_keywords): Drop nothrow.

gcc/cp/ChangeLog:

	* constraint.cc (diagnose_trait_expr): Say "nothrow" without quotes
	rather than in quotes.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp2a/concepts-traits3.C: Adjust expected diagnostics.
---
 gcc/c-family/c-format.cc                      |  3 +--
 gcc/cp/constraint.cc                          | 14 +++++++-------
 gcc/testsuite/g++.dg/cpp2a/concepts-traits3.C |  8 ++++----
 3 files changed, 12 insertions(+), 13 deletions(-)

diff --git a/gcc/c-family/c-format.cc b/gcc/c-family/c-format.cc
index a6c380bf1c8..a2026591ed1 100644
--- a/gcc/c-family/c-format.cc
+++ b/gcc/c-family/c-format.cc
@@ -2900,7 +2900,7 @@ static const token_t cxx_opers[] =
   };
 
 /* Common C/C++ keywords that are expected to be quoted within the format
-   string.  Keywords like auto, inline, or volatile are exccluded because
+   string.  Keywords like auto, inline, or volatile are excluded because
    they are sometimes used in common terms like /auto variables/, /inline
    function/, or /volatile access/ where they should not be quoted.  */
 
@@ -2927,7 +2927,6 @@ static const token_t c_keywords[] =
    NAME ("noinline", NULL),
    NAME ("nonnull", NULL),
    NAME ("noreturn", NULL),
-   NAME ("nothrow", NULL),
    NAME ("offsetof", NULL),
    NAME ("readonly", "read-only"),
    NAME ("readwrite", "read-write"),
diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
index 5839bfb4b52..266ec581a20 100644
--- a/gcc/cp/constraint.cc
+++ b/gcc/cp/constraint.cc
@@ -3592,13 +3592,13 @@ diagnose_trait_expr (tree expr, tree args)
   switch (TRAIT_EXPR_KIND (expr))
     {
     case CPTK_HAS_NOTHROW_ASSIGN:
-      inform (loc, "  %qT is not %<nothrow%> copy assignable", t1);
+      inform (loc, "  %qT is not nothrow copy assignable", t1);
       break;
     case CPTK_HAS_NOTHROW_CONSTRUCTOR:
-      inform (loc, "  %qT is not %<nothrow%> default constructible", t1);
+      inform (loc, "  %qT is not nothrow default constructible", t1);
       break;
     case CPTK_HAS_NOTHROW_COPY:
-      inform (loc, "  %qT is not %<nothrow%> copy constructible", t1);
+      inform (loc, "  %qT is not nothrow copy constructible", t1);
       break;
     case CPTK_HAS_TRIVIAL_ASSIGN:
       inform (loc, "  %qT is not trivially copy assignable", t1);
@@ -3674,7 +3674,7 @@ diagnose_trait_expr (tree expr, tree args)
       inform (loc, "  %qT is not trivially assignable from %qT", t1, t2);
       break;
     case CPTK_IS_NOTHROW_ASSIGNABLE:
-      inform (loc, "  %qT is not %<nothrow%> assignable from %qT", t1, t2);
+      inform (loc, "  %qT is not nothrow assignable from %qT", t1, t2);
       break;
     case CPTK_IS_CONSTRUCTIBLE:
       if (!t2)
@@ -3690,9 +3690,9 @@ diagnose_trait_expr (tree expr, tree args)
       break;
     case CPTK_IS_NOTHROW_CONSTRUCTIBLE:
       if (!t2)
-	inform (loc, "  %qT is not %<nothrow%> default constructible", t1);
+	inform (loc, "  %qT is not nothrow default constructible", t1);
       else
-	inform (loc, "  %qT is not %<nothrow%> constructible from %qE", t1, t2);
+	inform (loc, "  %qT is not nothrow constructible from %qE", t1, t2);
       break;
     case CPTK_HAS_UNIQUE_OBJ_REPRESENTATIONS:
       inform (loc, "  %qT does not have unique object representations", t1);
@@ -3701,7 +3701,7 @@ diagnose_trait_expr (tree expr, tree args)
       inform (loc, "  %qT is not convertible from %qE", t2, t1);
       break;
     case CPTK_IS_NOTHROW_CONVERTIBLE:
-	inform (loc, "  %qT is not %<nothrow%> convertible from %qE", t2, t1);
+	inform (loc, "  %qT is not nothrow convertible from %qE", t2, t1);
       break;
     case CPTK_REF_CONSTRUCTS_FROM_TEMPORARY:
       inform (loc, "  %qT is not a reference that binds to a temporary "
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-traits3.C b/gcc/testsuite/g++.dg/cpp2a/concepts-traits3.C
index f20608b6918..3e87da4611e 100644
--- a/gcc/testsuite/g++.dg/cpp2a/concepts-traits3.C
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-traits3.C
@@ -21,7 +21,7 @@ concept TriviallyAssignable = __is_trivially_assignable(T, U);
 
 template<class T, class U>
 concept NothrowAssignable = __is_nothrow_assignable(T, U);
-// { dg-message "'S' is not 'nothrow' assignable from 'int'" "" { target *-*-* } .-1  }
+// { dg-message "'S' is not nothrow assignable from 'int'" "" { target *-*-* } .-1  }
 
 template<class T, class... Args>
 concept Constructible = __is_constructible(T, Args...);
@@ -37,9 +37,9 @@ concept TriviallyConstructible = __is_trivially_constructible(T, Args...);
 
 template<class T, class... Args>
 concept NothrowConstructible = __is_nothrow_constructible(T, Args...);
-// { dg-message "'S' is not 'nothrow' default constructible" "" { target *-*-* } .-1  }
-// { dg-message "'S' is not 'nothrow' constructible from 'int'" "" { target *-*-* } .-2  }
-// { dg-message "'S' is not 'nothrow' constructible from 'int, char'" "" { target *-*-* } .-3  }
+// { dg-message "'S' is not nothrow default constructible" "" { target *-*-* } .-1  }
+// { dg-message "'S' is not nothrow constructible from 'int'" "" { target *-*-* } .-2  }
+// { dg-message "'S' is not nothrow constructible from 'int, char'" "" { target *-*-* } .-3  }
 
 template<class T>
 concept UniqueObjReps = __has_unique_object_representations(T);

base-commit: 7701ea4a70a5a5c0fd977da90a30ffc4f3f87617
-- 
2.37.3