[C++ PATCH take #2] PR c++/96442: Improved error recovery in enumerations.

["Roger Sayle" <roger@nextmovesoftware.com>]

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Hi Jason,
My apologies for the long delay, but I've finally got around to
implementing your suggested improvements (implied by your review):
https://gcc.gnu.org/pipermail/gcc-patches/2022-March/591504.html
of my patch for PR c++/96442:
https://gcc.gnu.org/pipermail/gcc-patches/2022-February/590716.html

The "How does that happen?" is insightful and leads to a cleaner
solution, setting ENUM_UNDERLYING_TYPE to integer_type_node when
issuing an error, so that this invariant holds during the parser's
error recovery.  I've also moved the new testcase to the g++.dg/parse
subdirectory as per your feedback on my previous ICE-on-invalid fixes.

This patch has been tested on x86_64-pc-linunx-gnu with make bootstrap
and make -k check with no new (unexpected) failures.  Ok for mainline?


2022-06-05  Roger Sayle  <roger@nextmovesoftware.com>

gcc/cp/ChangeLog
        PR c++/96442
        * decl.cc (start_enum): When emitting a "must be integral" error,
        set ENUM_UNDERLYING_TYPE to integer_type_node, to avoid an ICE
        downstream in build_enumeration.

gcc/testsuite/ChangeLog
        PR c++/96442
        * g++.dg/parse/pr96442.C: New test cae.

Thanks again,
Roger
--

> -----Original Message-----
> From: Jason Merrill <jason@redhat.com>
> Sent: 10 March 2022 05:06
> To: Roger Sayle <roger@nextmovesoftware.com>; gcc-patches@gcc.gnu.org
> Subject: Re: [C++ PATCH] PR c++/96442: Another improved error recovery in
> enumerations.
> 
> On 2/22/22 08:02, Roger Sayle wrote:
> >
> > This patch resolves PR c++/96442, another ICE-after-error regression.
> > In this case, invalid code attempts to use a non-integral type as the
> > underlying type for an enumeration (a record_type in the example given
> > in the bugzilla PR), for which the parser emits an error message but
> > allows the inappropriate type to leak to downstream code.
> 
> How does that happen?
> 
> Would it help to change dependent_type_p in start_enum to
> WILDCARD_TYPE_P?
> 
> > The minimal
> > safe fix is to double check that the enumeration's underlying type
> > EUTYPE satisfies INTEGRAL_TYPE_P before calling int_fits_type_p in
> > build_enumerator.  This is a one line fix, but correcting indentation
> > and storing a common subexpression in a variable makes the change look
> > a little bigger.
> >
> > This patch has been tested on x86_64-pc-linunx-gnu with make bootstrap
> > and make -k check with no new (unexpected) failures.  Ok for mainline?
> >
> >
> > 2022-02-22  Roger Sayle  <roger@nextmovesoftware.com>
> >
> > gcc/cp/ChangeLog
> > 	PR c++/96442
> > 	* decl.cc (build_enumeration): Check ENUM_UNDERLYING_TYPE is
> > 	INTEGRAL_TYPE_P before calling int_fits_type_p.
> >
> > gcc/testsuite/ChangeLog
> > 	PR c++/96442
> > 	* g++.dg/pr96442.C: New test cae.
> >
> >
> > Thanks in advance,
> > Roger
> > --
> >


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diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index e0d397d..ca735d3 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -16306,8 +16306,11 @@ start_enum (tree name, tree enumtype, tree underlying_type,
       else if (dependent_type_p (underlying_type))
 	ENUM_UNDERLYING_TYPE (enumtype) = underlying_type;
       else
-        error ("underlying type %qT of %qT must be an integral type", 
-               underlying_type, enumtype);
+	{
+	  error ("underlying type %qT of %qT must be an integral type", 
+		 underlying_type, enumtype);
+	  ENUM_UNDERLYING_TYPE (enumtype) = integer_type_node;
+	}
     }
 
   /* If into a template class, the returned enum is always the first
diff --git a/gcc/testsuite/g++.dg/parse/pr96442.C b/gcc/testsuite/g++.dg/parse/pr96442.C
new file mode 100644
index 0000000..235bb11
--- /dev/null
+++ b/gcc/testsuite/g++.dg/parse/pr96442.C
@@ -0,0 +1,6 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+enum struct a : struct {};
+template <class b> enum class a : class c{};
+enum struct a {b};
+// { dg-excess-errors "" }