c: Handle C_TYPE_INCOMPLETE_VARS even for ENUMERAL_TYPEs [PR94172]

The following testcases ICE, because they contain extern variable
declarations with incomplete enum types that is later completed and after
that those variables are accessed.  The ICEs are because the vars then may have
incorrect DECL_MODE etc., e.g. in the first case the var has SImode
DECL_MODE (the guessed mode for the enum), but the enum then actually has
DImode because its enumerators don't fit into unsigned int.

The following patch fixes it by using C_TYPE_INCOMPLETE_VARS not just on
incomplete struct/union types, but also incomplete enum types.
TYPE_VFIELD can't be used as it is TYPE_MIN_VALUE on ENUMERAL_TYPE,
thankfully TYPE_LANG_SLOT_1 has been used in the C FE only on
FUNCTION_TYPEs.

2020-03-17  Jakub Jelinek  <jakub@redhat.com>

	PR c/94172
	* c-tree.h (C_TYPE_INCOMPLETE_VARS): Define to TYPE_LANG_SLOT_1
	instead of TYPE_VFIELD, and support it on {RECORD,UNION,ENUMERAL}_TYPE.
	(TYPE_ACTUAL_ARG_TYPES): Check that it is only used on FUNCTION_TYPEs.
	* c-decl.c (pushdecl): Push C_TYPE_INCOMPLETE_VARS also to
	ENUMERAL_TYPEs.
	(finish_incomplete_vars): New function, moved from finish_struct.  Use
	relayout_decl instead of layout_decl.
	(finish_struct): Remove obsolete comment about C_TYPE_INCOMPLETE_VARS
	being TYPE_VFIELD.  Use finish_incomplete_vars.
	(finish_enum): Clear C_TYPE_INCOMPLETE_VARS.  Call
	finish_incomplete_vars.
	* c-typeck.c (c_build_qualified_type): Clear C_TYPE_INCOMPLETE_VARS
	also on ENUMERAL_TYPEs.

	* gcc.dg/pr94172-1.c: New test.
	* gcc.dg/pr94172-2.c: New test.

7 files changed, 89 insertions, 28 deletions

diff --git a/gcc/c/ChangeLog b/gcc/c/ChangeLog
index 240859e..25f8f5b 100644
--- a/gcc/c/ChangeLog
+++ b/gcc/c/ChangeLog
@@ -1,3 +1,20 @@
+2020-03-17  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c/94172
+	* c-tree.h (C_TYPE_INCOMPLETE_VARS): Define to TYPE_LANG_SLOT_1
+	instead of TYPE_VFIELD, and support it on {RECORD,UNION,ENUMERAL}_TYPE.
+	(TYPE_ACTUAL_ARG_TYPES): Check that it is only used on FUNCTION_TYPEs.
+	* c-decl.c (pushdecl): Push C_TYPE_INCOMPLETE_VARS also to
+	ENUMERAL_TYPEs.
+	(finish_incomplete_vars): New function, moved from finish_struct.  Use
+	relayout_decl instead of layout_decl.
+	(finish_struct): Remove obsolete comment about C_TYPE_INCOMPLETE_VARS
+	being TYPE_VFIELD.  Use finish_incomplete_vars.
+	(finish_enum): Clear C_TYPE_INCOMPLETE_VARS.  Call
+	finish_incomplete_vars.
+	* c-typeck.c (c_build_qualified_type): Clear C_TYPE_INCOMPLETE_VARS
+	also on ENUMERAL_TYPEs.
+
 2020-03-16  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c/94179
diff --git a/gcc/c/c-decl.c b/gcc/c/c-decl.c
index 87a0734..ed5163d 100644
--- a/gcc/c/c-decl.c
+++ b/gcc/c/c-decl.c
@@ -3312,7 +3312,8 @@ pushdecl (tree x)
 	element = TREE_TYPE (element);
       element = TYPE_MAIN_VARIANT (element);
 
-      if (RECORD_OR_UNION_TYPE_P (element)
+      if ((RECORD_OR_UNION_TYPE_P (element)
+	   || TREE_CODE (element) == ENUMERAL_TYPE)
 	  && (TREE_CODE (x) != TYPE_DECL
 	      || TREE_CODE (TREE_TYPE (x)) == ARRAY_TYPE)
 	  && !COMPLETE_TYPE_P (element))
@@ -8354,6 +8355,26 @@ field_decl_cmp (const void *x_p, const void *y_p)
   return 1;
 }
 
+/* If this structure or union completes the type of any previous
+   variable declaration, lay it out and output its rtl.  */
+static void
+finish_incomplete_vars (tree incomplete_vars, bool toplevel)
+{
+  for (tree x = incomplete_vars; x; x = TREE_CHAIN (x))
+    {
+      tree decl = TREE_VALUE (x);
+      if (TREE_CODE (TREE_TYPE (decl)) == ARRAY_TYPE)
+	layout_array_type (TREE_TYPE (decl));
+      if (TREE_CODE (decl) != TYPE_DECL)
+	{
+	  relayout_decl (decl);
+	  if (c_dialect_objc ())
+	    objc_check_decl (decl);
+	  rest_of_decl_compilation (decl, toplevel, 0);
+	}
+    }
+}
+
 /* Fill in the fields of a RECORD_TYPE or UNION_TYPE node, T.
    LOC is the location of the RECORD_TYPE or UNION_TYPE's definition.
    FIELDLIST is a chain of FIELD_DECL nodes for the fields.
@@ -8612,13 +8633,6 @@ finish_struct (location_t loc, tree t, tree fieldlist, tree attributes,
       warning_at (loc, 0, "union cannot be made transparent");
     }
 
-  /* Note: C_TYPE_INCOMPLETE_VARS overloads TYPE_VFIELD which is used
-     in dwarf2out via rest_of_decl_compilation below and means
-     something totally different.  Since we will be clearing
-     C_TYPE_INCOMPLETE_VARS shortly after we iterate through them,
-     clear it ahead of time and avoid problems in dwarf2out.  Ideally,
-     C_TYPE_INCOMPLETE_VARS should use some language specific
-     node.  */
   tree incomplete_vars = C_TYPE_INCOMPLETE_VARS (TYPE_MAIN_VARIANT (t));
   for (x = TYPE_MAIN_VARIANT (t); x; x = TYPE_NEXT_VARIANT (x))
     {
@@ -8639,21 +8653,7 @@ finish_struct (location_t loc, tree t, tree fieldlist, tree attributes,
   /* Finish debugging output for this type.  */
   rest_of_type_compilation (t, toplevel);
 
-  /* If this structure or union completes the type of any previous
-     variable declaration, lay it out and output its rtl.  */
-  for (x = incomplete_vars; x; x = TREE_CHAIN (x))
-    {
-      tree decl = TREE_VALUE (x);
-      if (TREE_CODE (TREE_TYPE (decl)) == ARRAY_TYPE)
-	layout_array_type (TREE_TYPE (decl));
-      if (TREE_CODE (decl) != TYPE_DECL)
-	{
-	  layout_decl (decl, 0);
-	  if (c_dialect_objc ())
-	    objc_check_decl (decl);
-	  rest_of_decl_compilation (decl, toplevel, 0);
-	}
-    }
+  finish_incomplete_vars (incomplete_vars, toplevel);
 
   /* If we're inside a function proper, i.e. not file-scope and not still
      parsing parameters, then arrange for the size of a variable sized type
@@ -8932,8 +8932,10 @@ finish_enum (tree enumtype, tree values, tree attributes)
   TYPE_LANG_SPECIFIC (enumtype) = lt;
 
   /* Fix up all variant types of this enum type.  */
+  tree incomplete_vars = C_TYPE_INCOMPLETE_VARS (TYPE_MAIN_VARIANT (enumtype));
   for (tem = TYPE_MAIN_VARIANT (enumtype); tem; tem = TYPE_NEXT_VARIANT (tem))
     {
+      C_TYPE_INCOMPLETE_VARS (tem) = NULL_TREE;
       if (tem == enumtype)
 	continue;
       TYPE_VALUES (tem) = TYPE_VALUES (enumtype);
@@ -8952,6 +8954,8 @@ finish_enum (tree enumtype, tree values, tree attributes)
   /* Finish debugging output for this type.  */
   rest_of_type_compilation (enumtype, toplevel);
 
+  finish_incomplete_vars (incomplete_vars, toplevel);
+
   /* If this enum is defined inside a struct, add it to
      struct_types.  */
   if (warn_cxx_compat
diff --git a/gcc/c/c-tree.h b/gcc/c/c-tree.h
index 7122992..364d7e0 100644
--- a/gcc/c/c-tree.h
+++ b/gcc/c/c-tree.h
@@ -38,9 +38,12 @@ along with GCC; see the file COPYING3.  If not see
    nonzero if the definition of the type has already started.  */
 #define C_TYPE_BEING_DEFINED(TYPE) TYPE_LANG_FLAG_0 (TYPE)
 
-/* In an incomplete RECORD_TYPE or UNION_TYPE, a list of variable
-   declarations whose type would be completed by completing that type.  */
-#define C_TYPE_INCOMPLETE_VARS(TYPE) TYPE_VFIELD (TYPE)
+/* In an incomplete RECORD_TYPE, UNION_TYPE or ENUMERAL_TYPE, a list of
+   variable declarations whose type would be completed by completing
+   that type.  */
+#define C_TYPE_INCOMPLETE_VARS(TYPE) \
+  TYPE_LANG_SLOT_1 (TREE_CHECK4 (TYPE, RECORD_TYPE, UNION_TYPE, \
+				 QUAL_UNION_TYPE, ENUMERAL_TYPE))
 
 /* In an IDENTIFIER_NODE, nonzero if this identifier is actually a
    keyword.  C_RID_CODE (node) is then the RID_* value of the keyword.  */
@@ -108,7 +111,8 @@ along with GCC; see the file COPYING3.  If not see
 /* For FUNCTION_TYPE, a hidden list of types of arguments.  The same as
    TYPE_ARG_TYPES for functions with prototypes, but created for functions
    without prototypes.  */
-#define TYPE_ACTUAL_ARG_TYPES(NODE) TYPE_LANG_SLOT_1 (NODE)
+#define TYPE_ACTUAL_ARG_TYPES(NODE) \
+  TYPE_LANG_SLOT_1 (FUNCTION_TYPE_CHECK (NODE))
 
 /* For a CONSTRUCTOR, whether some initializer contains a
    subexpression meaning it is not a constant expression.  */
diff --git a/gcc/c/c-typeck.c b/gcc/c/c-typeck.c
index 490d8fc..385bf3a 100644
--- a/gcc/c/c-typeck.c
+++ b/gcc/c/c-typeck.c
@@ -15207,7 +15207,8 @@ c_build_qualified_type (tree type, int type_quals, tree orig_qual_type,
 		   : build_qualified_type (type, type_quals));
   /* A variant type does not inherit the list of incomplete vars from the
      type main variant.  */
-  if (RECORD_OR_UNION_TYPE_P (var_type)
+  if ((RECORD_OR_UNION_TYPE_P (var_type)
+       || TREE_CODE (var_type) == ENUMERAL_TYPE)
       && TYPE_MAIN_VARIANT (var_type) != var_type)
     C_TYPE_INCOMPLETE_VARS (var_type) = 0;
   return var_type;
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 45fb829..dae22c2 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,5 +1,9 @@
 2020-03-17  Jakub Jelinek  <jakub@redhat.com>
 
+	PR c/94172
+	* gcc.dg/pr94172-1.c: New test.
+	* gcc.dg/pr94172-2.c: New test.
+
 	PR c++/90995
 	* g++.dg/cpp0x/enum40.C: New test.
 
diff --git a/gcc/testsuite/gcc.dg/pr94172-1.c b/gcc/testsuite/gcc.dg/pr94172-1.c
new file mode 100644
index 0000000..12f84af
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr94172-1.c
@@ -0,0 +1,12 @@
+/* PR c/94172 */
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+extern enum E e;
+enum E { l = 0x100000000ULL };
+
+unsigned long long
+foo (void)
+{
+  return e;
+}
diff --git a/gcc/testsuite/gcc.dg/pr94172-2.c b/gcc/testsuite/gcc.dg/pr94172-2.c
new file mode 100644
index 0000000..bb7b060
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr94172-2.c
@@ -0,0 +1,19 @@
+/* PR c/94172 */
+/* { dg-do compile } */
+/* { dg-options "-Os -g -fshort-enums" } */
+
+extern enum E e;
+extern void bar (int a);
+enum E { F };
+
+void
+foo (int a)
+{
+  int l = e;
+  if (a)
+    {
+      __asm volatile ("nop");
+      l = 0;
+    }
+  bar (l);
+}