[v2 PATCH] c++: ICE with erroneous template redeclaration [PR106311]

[Marek Polacek <polacek@redhat.com>]

On Fri, Jul 22, 2022 at 05:21:58PM -0400, Jason Merrill wrote:
> On 7/15/22 11:29, Marek Polacek wrote:
> > Here we ICE trying to get DECL_SOURCE_LOCATION of the parm that happens
> > to be error_mark_node in this ill-formed test.  I kept running into this
> > while reducing code, so it'd be good to have it fixed.
> > 
> > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
> > 
> > 	PR c++/106311
> > 
> > gcc/cp/ChangeLog:
> > 
> > 	* pt.cc (redeclare_class_template): Check DECL_P before accessing
> > 	DECL_SOURCE_LOCATION.
> > 
> > gcc/testsuite/ChangeLog:
> > 
> > 	* g++.dg/template/redecl5.C: New test.
> > ---
> >   gcc/cp/pt.cc                            | 3 ++-
> >   gcc/testsuite/g++.dg/template/redecl5.C | 5 +++++
> >   2 files changed, 7 insertions(+), 1 deletion(-)
> >   create mode 100644 gcc/testsuite/g++.dg/template/redecl5.C
> > 
> > diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> > index 718dfa5bfa8..0a294e91a79 100644
> > --- a/gcc/cp/pt.cc
> > +++ b/gcc/cp/pt.cc
> > @@ -6377,7 +6377,8 @@ redeclare_class_template (tree type, tree parms, tree cons)
> >   	{
> >   	  auto_diagnostic_group d;
> >   	  error ("template parameter %q+#D", tmpl_parm);
> > -	  inform (DECL_SOURCE_LOCATION (parm), "redeclared here as %q#D", parm);
> > +	  inform (DECL_P (parm) ? DECL_SOURCE_LOCATION (parm) : input_location,
> > +		  "redeclared here as %q#D", parm);
> 
> If we're checking DECL_P, probably we also should avoid passing it to %q#D
> if it's false?

Right, I suppose printing "<error node>" isn't all that helpful.  How about
this?

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

-- >8 --
Here we ICE trying to get DECL_SOURCE_LOCATION of the parm that happens
to be error_mark_node in this ill-formed test.  I kept running into this
while reducing code, so it'd be good to have it fixed.

	PR c++/106311

gcc/cp/ChangeLog:

	* pt.cc (redeclare_class_template): Check DECL_P before accessing
	DECL_SOURCE_LOCATION.

gcc/testsuite/ChangeLog:

	* g++.dg/template/redecl5.C: New test.
---
 gcc/cp/pt.cc                            | 5 ++++-
 gcc/testsuite/g++.dg/template/redecl5.C | 5 +++++
 2 files changed, 9 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/template/redecl5.C

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index c415db304c9..6c581fe0fb7 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -6377,7 +6377,10 @@ redeclare_class_template (tree type, tree parms, tree cons)
 	{
 	  auto_diagnostic_group d;
 	  error ("template parameter %q+#D", tmpl_parm);
-	  inform (DECL_SOURCE_LOCATION (parm), "redeclared here as %q#D", parm);
+	  if (DECL_P (parm))
+	    inform (DECL_SOURCE_LOCATION (parm), "redeclared here as %q#D", parm);
+	  else
+	    inform (input_location, "redeclared here");
 	  return false;
 	}
 
diff --git a/gcc/testsuite/g++.dg/template/redecl5.C b/gcc/testsuite/g++.dg/template/redecl5.C
new file mode 100644
index 00000000000..fb2d698e6bc
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/redecl5.C
@@ -0,0 +1,5 @@
+// PR c++/106311
+// { dg-do compile }
+
+template <typename, long> struct array; // { dg-error "template parameter" }
+template <typename, size_t X> struct array { }; // { dg-error "declared" }

base-commit: 16aafa3194d4851a07cc204f56a5f0618f77e5d7
-- 
2.37.1