[PATCH v2] c++: Check invalid use of constrained auto with trailing return type [PR100589]
Add check for constrained auto type specifier in function declaration or
function type declaration with trailing return type. Issue error if such
usage is detected.
Test file renamed, and added a new test for type declaration.
Successfully bootstrapped and regretested on x86_64-pc-linux-gnu:
Added 6 passed and 4 unsupported tests.
PR c++/100589
gcc/cp/ChangeLog:
* decl.cc (grokdeclarator): Issue an error for a declarator with
constrained auto type specifier and trailing return types. Include
function names if available.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/concepts-pr100589.C: New test.
Signed-off-by: Da Xie
---
gcc/cp/decl.cc | 13 +
gcc/testsuite/g++.dg/cpp2a/concepts-pr100589.C | 9 +
2 files changed, 22 insertions(+)
create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-pr100589.C
diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index 9ca8c6c4481..337ee65752e 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -14037,6 +14037,19 @@ grokdeclarator (const cp_declarator *declarator,
"invalid use of %");
return error_mark_node;
}
+ else if (is_constrained_auto (type))
+ {
+ if (funcdecl_p)
+ error_at (typespec_loc,
+ "%qs function with trailing return type "
+ "has constrained % type specifier "
+ "rather than plain %",
+ name);
+ else
+ error_at (typespec_loc,
+ "invalid use of constrained % type");
+ return error_mark_node;
+ }
tree tmpl = CLASS_PLACEHOLDER_TEMPLATE (auto_node);
if (!tmpl)
if (tree late_auto = type_uses_auto (late_return_type))
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-pr100589.C
b/gcc/testsuite/g++.dg/cpp2a/concepts-pr100589.C
new file mode 100644
index 000..0c60d31f29b
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-pr100589.C
@@ -0,0 +1,9 @@
+// PR c++/100589
+// { dg-do compile { target c++20 } }
+
+template
+concept false_concept = false;
+
+false_concept auto f() -> int; // { dg-error "'f' .* trailing return type.*
constrained 'auto'" }
+
+using type = false_concept auto() -> int; // { dg-error "invalid use of
constrained 'auto' type"}
--
2.34.1
Re: Re: [PATCH v2] c++: Check invalid use of constrained auto with trailing return type [PR100589]
* Patrick Palka [2025-03-05 11:15:06]:
> On Tue, 4 Mar 2025, Patrick Palka wrote:
>
> > On Sun, 2 Mar 2025, Da Xie wrote:
> >
> > > Add check for constrained auto type specifier in function declaration or
> > > function type declaration with trailing return type. Issue error if such
> > > usage is detected.
> > >
> > > Test file renamed, and added a new test for type declaration.
> > >
> > > Successfully bootstrapped and regretested on x86_64-pc-linux-gnu:
> > > Added 6 passed and 4 unsupported tests.
> > >
> > > PR c++/100589
> > >
> > > gcc/cp/ChangeLog:
> > >
> > > * decl.cc (grokdeclarator): Issue an error for a declarator with
> > > constrained auto type specifier and trailing return types. Include
> > > function names if available.
> > >
> > > gcc/testsuite/ChangeLog:
> > >
> > > * g++.dg/cpp2a/concepts-pr100589.C: New test.
> >
> > LGTM, thanks! Jason, shall I push this to trunk?
>
> Pushed as r15-7834-g7439febd94368f.
>
Many thanks! I'm a GCC newbie, and this reviewing process has taught me a lot.
> >
> > >
> > > Signed-off-by: Da Xie
> > > ---
> > > gcc/cp/decl.cc | 13 +
> > > gcc/testsuite/g++.dg/cpp2a/concepts-pr100589.C | 9 +
> > > 2 files changed, 22 insertions(+)
> > > create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-pr100589.C
> > >
> > > diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
> > > index 9ca8c6c4481..337ee65752e 100644
> > > --- a/gcc/cp/decl.cc
> > > +++ b/gcc/cp/decl.cc
> > > @@ -14037,6 +14037,19 @@ grokdeclarator (const cp_declarator *declarator,
> > > "invalid use of %");
> > > return error_mark_node;
> > > }
> > > + else if (is_constrained_auto (type))
> > > + {
> > > + if (funcdecl_p)
> > > + error_at (typespec_loc,
> > > + "%qs function with trailing return type "
> > > + "has constrained % type specifier "
> > > + "rather than plain %",
> > > + name);
> > > + else
> > > + error_at (typespec_loc,
> > > + "invalid use of constrained % type");
> > > + return error_mark_node;
> > > + }
> > > tree tmpl = CLASS_PLACEHOLDER_TEMPLATE (auto_node);
> > > if (!tmpl)
> > > if (tree late_auto = type_uses_auto (late_return_type))
> > > diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-pr100589.C
> > > b/gcc/testsuite/g++.dg/cpp2a/concepts-pr100589.C
> > > new file mode 100644
> > > index 000..0c60d31f29b
> > > --- /dev/null
> > > +++ b/gcc/testsuite/g++.dg/cpp2a/concepts-pr100589.C
> > > @@ -0,0 +1,9 @@
> > > +// PR c++/100589
> > > +// { dg-do compile { target c++20 } }
> > > +
> > > +template
> > > +concept false_concept = false;
> > > +
> > > +false_concept auto f() -> int; // { dg-error "'f' .* trailing return
> > > type.* constrained 'auto'" }
> >
> > I can replace the use of .* with \[^\r\n\]* before pushing.
> >
> > > +
> > > +using type = false_concept auto() -> int; // { dg-error "invalid use of
> > > constrained 'auto' type"}
>
> N.B. I added a missing space between the " and } that caused this
> dircetive to get ignored.
>
Sorry for the misses. I fixed and checked it locally, and the test
passed.
> > > --
> > > 2.34.1
> > >
> > >
> >
[PATCH] c++: Check invalid use of constrained auto with trailing return type [PR100589]
This bug comes from a missing check when a function declaration has a
late-specified return type and a constrained auto type specifier. By
adding such a check, we can catch such uses and diagnose them as errors.
Successfully bootstrapped and regretested on x86_64-pc-linux-gnu:
adds 6 new test results and 4 UNSUPPORTED results to g++.sum. The 4
UNSUPPORTED results are due to the fact that concepts are not supported
before c++20, so tests cannot pass with c++17 and lower standards.
PR c++/100589
gcc/cp/ChangeLog:
* decl.cc (grokdeclarator): Issue an error for a declarator with
constrained auto type specifier and trailing return types.
gcc/testsuite/ChangeLog:
* g++.dg/other/pr100589.C: New test.
Signed-off-by: Da Xie
---
gcc/cp/decl.cc| 7 +++
gcc/testsuite/g++.dg/other/pr100589.C | 7 +++
2 files changed, 14 insertions(+)
create mode 100644 gcc/testsuite/g++.dg/other/pr100589.C
diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index 9ca8c6c4481..f283ed996a2 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -14037,6 +14037,13 @@ grokdeclarator (const cp_declarator *declarator,
"invalid use of %");
return error_mark_node;
}
+ else if (is_constrained_auto (type))
+ {
+ error_at (typespec_loc, "invalid use of "
+ "constrained auto type specifier "
+ "in function with trailing return type");
+ return error_mark_node;
+ }
tree tmpl = CLASS_PLACEHOLDER_TEMPLATE (auto_node);
if (!tmpl)
if (tree late_auto = type_uses_auto (late_return_type))
diff --git a/gcc/testsuite/g++.dg/other/pr100589.C
b/gcc/testsuite/g++.dg/other/pr100589.C
new file mode 100644
index 000..3fa054ed34d
--- /dev/null
+++ b/gcc/testsuite/g++.dg/other/pr100589.C
@@ -0,0 +1,7 @@
+// PR c++/100589
+// { dg-do compile { target c++20 } }
+
+template
+concept false_concept = false;
+
+false_concept auto f() -> int; // { dg-error "constrained auto type
specifier.* trailing return type" }
\ No newline at end of file
--
2.34.1
