Re: C PATCH for c/68668 (grokdeclarator and wrong type of PARM_DECL)

[Marek Polacek <polacek@redhat.com>]

On Thu, Dec 03, 2015 at 09:40:29PM +0000, Joseph Myers wrote:
> On Thu, 3 Dec 2015, Marek Polacek wrote:
> 
> > > I think you also need to decrement orig_qual_indirect, which counts the 
> > > number of levels of array type derivation from orig_qual_type.
> > 
> > Thus:
> > 
> > Bootstrapped/regtested on x86_64-linux, ok for trunk?
> > 
> > 2015-12-03  Marek Polacek  <polacek@redhat.com>
> > 
> > 	PR c/68668
> > 	* c-decl.c (grokdeclarator): When creating a PARM_DECL of ARRAY_TYPE,
> > 	use TREE_TYPE of orig_qual_type.  Decrement ORIG_QUAL_INDIRECT.
> 
> On further consideration:
> 
> Removing one level of array type derivation from type means it is one 
> fewer levels indirect from the original version of orig_qual_type.  So I 
> think you should actually decrement orig_qual_indirect without changing 
> orig_qual_type.  But, if orig_qual_indirect is indirect, in that case you 
> may get better results from changing orig_qual_type without decrementing 
> orig_qual_indirect.

I think I don't quite understand the last part of this, but here's the patch
anyway.  Having added more testcases, I noticed that my last version indeed
wasn't really correct -- thanks for spotting that.

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

2015-12-07  Marek Polacek  <polacek@redhat.com>

	PR c/68668
	* c-decl.c (grokdeclarator): If ORIG_QUAL_INDIRECT is indirect, use
	TREE_TYPE of ORIG_QUAL_TYPE, otherwise decrement ORIG_QUAL_INDIRECT.

	* gcc.dg/pr68668.c: New test.

diff --git gcc/c/c-decl.c gcc/c/c-decl.c
index 9ad8219..6a85514 100644
--- gcc/c/c-decl.c
+++ gcc/c/c-decl.c
@@ -6417,6 +6417,13 @@ grokdeclarator (const struct c_declarator *declarator,
 	  {
 	    /* Transfer const-ness of array into that of type pointed to.  */
 	    type = TREE_TYPE (type);
+	    if (orig_qual_type != NULL_TREE)
+	      {
+		if (orig_qual_indirect != 0)
+		  orig_qual_type = TREE_TYPE (orig_qual_type);
+		else
+		  orig_qual_indirect--;
+	      }
 	    if (type_quals)
 	      type = c_build_qualified_type (type, type_quals, orig_qual_type,
 					     orig_qual_indirect);
diff --git gcc/testsuite/gcc.dg/pr68668.c gcc/testsuite/gcc.dg/pr68668.c
index e69de29..d013aa9 100644
--- gcc/testsuite/gcc.dg/pr68668.c
+++ gcc/testsuite/gcc.dg/pr68668.c
@@ -0,0 +1,53 @@
+/* PR c/68668 */
+/* { dg-do compile } */
+
+typedef const int T[];
+typedef const int U[1];
+
+int
+fn1 (T p)
+{
+  return p[0];
+}
+
+int
+fn2 (U p[2])
+{
+  return p[0][0];
+}
+
+int
+fn3 (U p[2][3])
+{
+  return p[0][0][0];
+}
+
+int
+fn4 (U *p)
+{
+  return p[0][0];
+}
+
+int
+fn5 (U (*p)[1])
+{
+  return (*p)[0][0];
+}
+
+int
+fn6 (U (*p)[1][2])
+{
+  return (*p)[0][0][0];
+}
+
+int
+fn7 (U **p)
+{
+  return p[0][0][0];
+}
+
+int
+fn8 (U (**p)[1])
+{
+  return (*p)[0][0][0];
+}

	Marek