Added warning on structures/unions that are empty or contain only

bit fields of zero size. Warnings are generated in C++ mode and if
only such type is defined inside extern "C" block.
The patch fixed PR5065.

Differential Revision: http://llvm-reviews.chandlerc.com/D2151

llvm-svn: 194653

2 files changed, 19 insertions, 2 deletions

diff --git a/clang/test/SemaCXX/extern-c.cpp b/clang/test/SemaCXX/extern-c.cpp
index 2bf95352259..dfbf38667c5 100644
--- a/clang/test/SemaCXX/extern-c.cpp
+++ b/clang/test/SemaCXX/extern-c.cpp
@@ -140,7 +140,7 @@ namespace N2 {
 
 // We allow all these even though the standard says they are ill-formed.
 extern "C" {
-  struct stat {};
+  struct stat {};   // expected-warning{{empty struct has size 0 in C, size 1 in C++}}
   void stat(struct stat);
 }
 namespace X {
@@ -187,3 +187,20 @@ namespace X {
   extern "C" double global_var_vs_extern_c_var_2; // expected-note {{here}}
 }
 int global_var_vs_extern_c_var_2; // expected-error {{conflicts with declaration with C language linkage}}
+
+template <class T> struct pr5065_n1 {};
+extern "C" {
+  union pr5065_1 {}; // expected-warning{{empty union has size 0 in C, size 1 in C++}}
+  struct pr5065_2 { int: 0; }; // expected-warning{{struct has size 0 in C, size 1 in C++}}
+  struct pr5065_3 {}; // expected-warning{{empty struct has size 0 in C, size 1 in C++}}
+  struct pr5065_4 { // expected-warning{{empty struct has size 0 in C, size 1 in C++}}
+    struct Inner {}; // expected-warning{{empty struct has size 0 in C, size 1 in C++}}
+  };
+  // These should not warn
+  class pr5065_n3 {};
+  pr5065_n1<int> pr5065_v;
+  struct pr5065_n4 { void m() {} };
+  struct pr5065_n5 : public pr5065_3 {};
+  struct pr5065_n6 : public virtual pr5065_3 {};
+}
+struct pr5065_n7 {};
diff --git a/clang/test/SemaCXX/storage-class.cpp b/clang/test/SemaCXX/storage-class.cpp
index 74121843e5e..decf1e7ac36 100644
--- a/clang/test/SemaCXX/storage-class.cpp
+++ b/clang/test/SemaCXX/storage-class.cpp
@@ -4,4 +4,4 @@ extern int PR6495b = 42; // expected-warning{{'extern' variable has an initializ
 extern const int PR6495c[] = {42,43,44};
 
 extern struct Test1 {}; // expected-warning {{'extern' is not permitted on a declaration of a type}}
-extern "C" struct Test0 {}; // no warning
+extern "C" struct Test0 { int x; }; // no warning