re PR c/24293 (Undefined behaviour not diagnosed with -fsyntax-only)

2016-01-15  Prathamesh Kulkarni  <prathamesh.kulkarni@linaro.org>

        PR c/24293
        * c-tree.h (incomplete_record_decls): Declare.
        * c-parser.c (incomplete_record_decls): Define.
        (c_parser_translation_unit): Iterate through incomplete_record_decls and
        report error if any decl has zero size.
        * c-decl.c (finish_decl): Append static decl with incomplete struct/union
        or enum type to incomplete_record_decls.

testsuite/
        * gcc.dg/pr24293.c: New test.
        * gcc.dg/Wcxx-compat-8.c: Adjust to accept error due to
        incomplete struct type.
        * gcc.dg/declspec-1.c: Likewise.
        * gcc.dg/pr63549.c: Likewise.

From-SVN: r232622

4 files changed, 37 insertions, 0 deletions

diff --git a/gcc/c/ChangeLog b/gcc/c/ChangeLog
index d11a822..697dd8d 100644
--- a/gcc/c/ChangeLog
+++ b/gcc/c/ChangeLog
@@ -1,3 +1,13 @@
+2016-01-15  Prathamesh Kulkarni  <prathamesh.kulkarni@linaro.org>
+
+	PR c/24293
+	* c-tree.h (incomplete_record_decls): Declare.
+	* c-parser.c (incomplete_record_decls): Define.
+	(c_parser_translation_unit): Iterate through incomplete_record_decls and
+	report error if any decl has zero size.
+	* c-decl.c (finish_decl): Append static decl with incomplete struct/union
+	or enum type to incomplete_record_decls.
+
 2016-01-14  Tom de Vries  <tom@codesourcery.com>
 
 	PR tree-optimization/68773
diff --git a/gcc/c/c-decl.c b/gcc/c/c-decl.c
index 5830e22..1ec6042 100644
--- a/gcc/c/c-decl.c
+++ b/gcc/c/c-decl.c
@@ -4791,6 +4791,12 @@ finish_decl (tree decl, location_t init_loc, tree init,
 	   TREE_TYPE (decl) = error_mark_node;
 	 }
 
+      if ((RECORD_OR_UNION_TYPE_P (TREE_TYPE (decl))
+	  || TREE_CODE (TREE_TYPE (decl)) == ENUMERAL_TYPE)
+	  && DECL_SIZE (decl) == NULL_TREE
+	  && TREE_STATIC (decl))
+	incomplete_record_decls.safe_push (decl);
+
       if (is_global_var (decl) && DECL_SIZE (decl) != 0)
 	{
 	  if (TREE_CODE (DECL_SIZE (decl)) == INTEGER_CST)
diff --git a/gcc/c/c-parser.c b/gcc/c/c-parser.c
index 919680a..efac47b 100644
--- a/gcc/c/c-parser.c
+++ b/gcc/c/c-parser.c
@@ -59,6 +59,15 @@ along with GCC; see the file COPYING3.  If not see
 #include "gimple-expr.h"
 #include "context.h"
 
+/* We need to walk over decls with incomplete struct/union/enum types
+   after parsing the whole translation unit.
+   In finish_decl(), if the decl is static, has incomplete
+   struct/union/enum type, it is appeneded to incomplete_record_decls.
+   In c_parser_translation_unit(), we iterate over incomplete_record_decls
+   and report error if any of the decls are still incomplete.  */ 
+
+vec<tree> incomplete_record_decls = vNULL;
+
 void
 set_c_expr_source_range (c_expr *expr,
 			 location_t start, location_t finish)
@@ -1421,6 +1430,16 @@ c_parser_translation_unit (c_parser *parser)
 	}
       while (c_parser_next_token_is_not (parser, CPP_EOF));
     }
+
+  for (unsigned i = 0; i < incomplete_record_decls.length (); ++i)
+    {
+      tree decl = incomplete_record_decls[i];
+      if (DECL_SIZE (decl) == NULL_TREE && TREE_TYPE (decl) != error_mark_node)
+	{
+	  error ("storage size of %q+D isn%'t known", decl);
+	  TREE_TYPE (decl) = error_mark_node;
+	}
+    }
 }
 
 /* Parse an external declaration (C90 6.7, C99 6.9).
diff --git a/gcc/c/c-tree.h b/gcc/c/c-tree.h
index 81a3d58..cf79ba7 100644
--- a/gcc/c/c-tree.h
+++ b/gcc/c/c-tree.h
@@ -731,4 +731,6 @@ set_c_expr_source_range (c_expr *expr,
 /* In c-fold.c */
 extern tree decl_constant_value_for_optimization (tree);
 
+extern vec<tree> incomplete_record_decls;
+
 #endif /* ! GCC_C_TREE_H */