c-decl.c (warn_cxx_compat_finish_struct): New parameters code, record_loc.

2015-06-03  Prathamesh Kulkarni  <prathamesh.kulkarni@linaro.org>

c/
        * c-decl.c (warn_cxx_compat_finish_struct): New parameters code, record_loc.
        Warn for empty struct.
        (finish_struct): Pass TREE_CODE(t) and loc to warn_cxx_compat_finish_struct.

testsuite/
        * gcc.dg/Wcxx-compat-22.c: New testcase.
        * c-c++-common/Wsizeof-pointer-memaccess1.c: Pass -Wno-c++-compat.
        * c-c++-common/Wsizeof-pointer-memaccess2.c: Likewise.
        * c-c++-common/pr58346-1.c: Likewise.
        * c-c++-common/transparent-union-1.c: Likewise.

From-SVN: r224083

8 files changed, 39 insertions, 2 deletions

diff --git a/gcc/c/ChangeLog b/gcc/c/ChangeLog
index a4bf620..69344bb 100644
--- a/gcc/c/ChangeLog
+++ b/gcc/c/ChangeLog
@@ -1,3 +1,9 @@
+2015-06-03  Prathamesh Kulkarni  <prathamesh.kulkarni@linaro.org>
+
+	* c-decl.c (warn_cxx_compat_finish_struct): New parameters code, record_loc.
+	Warn for empty struct.
+	(finish_struct): Pass TREE_CODE(t) and loc to warn_cxx_compat_finish_struct.
+
 2015-06-02  Andres Tiraboschi  <andres.tiraboschi@tallertechnologies.com>
 
 	* c-decl.c (start_function): Call plugin before parsing.
diff --git a/gcc/c/c-decl.c b/gcc/c/c-decl.c
index efdf902..efb978b 100644
--- a/gcc/c/c-decl.c
+++ b/gcc/c/c-decl.c
@@ -7525,12 +7525,23 @@ detect_field_duplicates (tree fieldlist)
 /* Finish up struct info used by -Wc++-compat.  */
 
 static void
-warn_cxx_compat_finish_struct (tree fieldlist)
+warn_cxx_compat_finish_struct (tree fieldlist, enum tree_code code,
+			       location_t record_loc)
 {
   unsigned int ix;
   tree x;
   struct c_binding *b;
 
+  if (fieldlist == NULL_TREE)
+    {
+      if (code == RECORD_TYPE)
+	warning_at (record_loc, OPT_Wc___compat,
+		    "empty struct has size 0 in C, size 1 in C++");
+      else
+	warning_at (record_loc, OPT_Wc___compat,
+		    "empty union has size 0 in C, size 1 in C++");
+    }
+
   /* Set the C_TYPE_DEFINED_IN_STRUCT flag for each type defined in
      the current struct.  We do this now at the end of the struct
      because the flag is used to issue visibility warnings, and we
@@ -7863,7 +7874,7 @@ finish_struct (location_t loc, tree t, tree fieldlist, tree attributes,
 			  DECL_EXPR, build_decl (loc, TYPE_DECL, NULL, t)));
 
   if (warn_cxx_compat)
-    warn_cxx_compat_finish_struct (fieldlist);
+    warn_cxx_compat_finish_struct (fieldlist, TREE_CODE (t), loc);
 
   struct_parse_info->struct_types.release ();
   struct_parse_info->fields.release ();
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 13e7ecb..efd859b 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,11 @@
+2015-06-03  Prathamesh Kulkarni  <prathamesh.kulkarni@linaro.org>
+
+	* gcc.dg/Wcxx-compat-22.c: New testcase.
+	* c-c++-common/Wsizeof-pointer-memaccess1.c: Pass -Wno-c++-compat.
+	* c-c++-common/Wsizeof-pointer-memaccess2.c: Likewise.
+	* c-c++-common/pr58346-1.c: Likewise.
+	* c-c++-common/transparent-union-1.c: Likewise.
+
 2015-06-02  Andres Tiraboschi  <andres.tiraboschi@tallertechnologies.com>
 
 	* g++.dg/plugin/plugin.exp: Add def-plugin-test.C.
diff --git a/gcc/testsuite/c-c++-common/Wsizeof-pointer-memaccess1.c b/gcc/testsuite/c-c++-common/Wsizeof-pointer-memaccess1.c
index 8e829d6..27c5da4 100644
--- a/gcc/testsuite/c-c++-common/Wsizeof-pointer-memaccess1.c
+++ b/gcc/testsuite/c-c++-common/Wsizeof-pointer-memaccess1.c
@@ -1,6 +1,7 @@
 /* Test -Wsizeof-pointer-memaccess warnings.  */
 /* { dg-do compile } */
 /* { dg-options "-Wall -Wno-sizeof-array-argument" } */
+/* { dg-options "-Wall -Wno-sizeof-array-argument -Wno-c++-compat" { target c } } */
 
 typedef __SIZE_TYPE__ size_t;
 #ifdef __cplusplus
diff --git a/gcc/testsuite/c-c++-common/Wsizeof-pointer-memaccess2.c b/gcc/testsuite/c-c++-common/Wsizeof-pointer-memaccess2.c
index fe17a70..e067d7d 100644
--- a/gcc/testsuite/c-c++-common/Wsizeof-pointer-memaccess2.c
+++ b/gcc/testsuite/c-c++-common/Wsizeof-pointer-memaccess2.c
@@ -1,6 +1,7 @@
 /* Test -Wsizeof-pointer-memaccess warnings.  */
 /* { dg-do compile } */
 /* { dg-options "-Wall -O2 -Wno-sizeof-array-argument" } */
+/* { dg-options "-Wall -O2 -Wno-sizeof-array-argument -Wno-c++-compat" {target c} } */
 
 #define bos(ptr) __builtin_object_size (ptr, 1)
 #define bos0(ptr) __builtin_object_size (ptr, 0)
diff --git a/gcc/testsuite/c-c++-common/pr58346-1.c b/gcc/testsuite/c-c++-common/pr58346-1.c
index 371fcf4..70a16d1 100644
--- a/gcc/testsuite/c-c++-common/pr58346-1.c
+++ b/gcc/testsuite/c-c++-common/pr58346-1.c
@@ -1,5 +1,6 @@
 /* PR c/58346 */
 /* { dg-do compile } */
+/* { dg-options "-Wno-c++-compat" { target c } } */
 
 struct U {
 #ifdef __cplusplus
diff --git a/gcc/testsuite/c-c++-common/transparent-union-1.c b/gcc/testsuite/c-c++-common/transparent-union-1.c
index 3fb6e782..91f2642 100644
--- a/gcc/testsuite/c-c++-common/transparent-union-1.c
+++ b/gcc/testsuite/c-c++-common/transparent-union-1.c
@@ -1,4 +1,5 @@
 /* PR c++/51228 */
+/* { dg-options "-Wno-c++-compat" { target c } } */
 
 typedef union {} U __attribute__((transparent_union)); /* { dg-warning "ignored" } */
 
diff --git a/gcc/testsuite/gcc.dg/Wcxx-compat-22.c b/gcc/testsuite/gcc.dg/Wcxx-compat-22.c
new file mode 100644
index 0000000..60b05ca
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/Wcxx-compat-22.c
@@ -0,0 +1,8 @@
+/* { dg-do compile } */
+/* { dg-options "-Wc++-compat" } */
+struct A {}; /* { dg-warning "empty struct has size 0 in C" } */
+union B {}; /* { dg-warning "empty union has size 0 in C" } */
+struct C { struct D {}; int x; }; /* { dg-warning "empty struct has size 0 in C|declaration does not declare anything" } */
+struct E { union F {}; int x; }; /* { dg-warning "empty union has size 0 in C|declaration does not declare anything" } */
+union G { union H {}; int x; }; /* { dg-warning "empty union has size 0 in C|declaration does not declare anything" } */
+union I { struct J {}; int x; }; /* { dg-warning "empty struct has size 0 in C|declaration does not declare anything" } */