From 0bfe54fdc83b7b4e37c40e652d86d15aa89885b2 Mon Sep 17 00:00:00 2001
From: Douglas Gregor <dgregor@apple.com>
Date: Tue, 10 Feb 2009 21:49:46 +0000
Subject: [PATCH] GNU allows structs with flexible array members to be placed
 inside arrays and other structs/unions as an extension. Downgrade our error
 to a warning. Fixes PR3540.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@64239 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/clang/Basic/DiagnosticSemaKinds.def |  2 +-
 lib/Sema/SemaType.cpp                       |  9 ++----
 test/Sema/array-constraint.c                |  2 +-
 test/Sema/flexible-array-init.c             | 32 +++++++++++++++++----
 4 files changed, 31 insertions(+), 14 deletions(-)

diff --git a/include/clang/Basic/DiagnosticSemaKinds.def b/include/clang/Basic/DiagnosticSemaKinds.def
index 9c879f740a..5dfe9d6f35 100644
--- a/include/clang/Basic/DiagnosticSemaKinds.def
+++ b/include/clang/Basic/DiagnosticSemaKinds.def
@@ -651,7 +651,7 @@ DIAG(err_flexible_array_empty_struct, ERROR,
      "flexible array %0 not allowed in otherwise empty struct")
 DIAG(ext_flexible_array_in_struct, EXTENSION,
      "%0 may not be nested in a struct due to flexible array member")
-DIAG(err_flexible_array_in_array, ERROR,
+DIAG(ext_flexible_array_in_array, EXTENSION,
      "%0 may not be used as an array element due to flexible array member")
 DIAG(err_flexible_array_init_nonempty, ERROR,
      "non-empty initialization of flexible array member inside subobject")
diff --git a/lib/Sema/SemaType.cpp b/lib/Sema/SemaType.cpp
index 25fd5c39fe..e898782f31 100644
--- a/lib/Sema/SemaType.cpp
+++ b/lib/Sema/SemaType.cpp
@@ -399,12 +399,9 @@ QualType Sema::GetTypeForDeclarator(Declarator &D, Scope *S, unsigned Skip) {
         D.setInvalidType(true);
       } else if (const RecordType *EltTy = T->getAsRecordType()) {
         // If the element type is a struct or union that contains a variadic
-        // array, reject it: C99 6.7.2.1p2.
-        if (EltTy->getDecl()->hasFlexibleArrayMember()) {
-          Diag(DeclType.Loc, diag::err_flexible_array_in_array) << T;
-          T = Context.IntTy;
-          D.setInvalidType(true);
-        }
+        // array, accept it as a GNU extension: C99 6.7.2.1p2.
+        if (EltTy->getDecl()->hasFlexibleArrayMember())
+          Diag(DeclType.Loc, diag::ext_flexible_array_in_array) << T;
       } else if (T->isObjCInterfaceType()) {
         Diag(DeclType.Loc, diag::warn_objc_array_of_interfaces) << T;
       }
diff --git a/test/Sema/array-constraint.c b/test/Sema/array-constraint.c
index d35b0acdfe..06b5d747ab 100644
--- a/test/Sema/array-constraint.c
+++ b/test/Sema/array-constraint.c
@@ -20,7 +20,7 @@ struct vari {
   int b[];
 };
 
-struct vari *func(struct vari a[]) { // expected-error {{'struct vari' may not be used as an array element due to flexible array member}}
+struct vari *func(struct vari a[]) { // expected-warning {{'struct vari' may not be used as an array element due to flexible array member}}
   return a;
 }
 
diff --git a/test/Sema/flexible-array-init.c b/test/Sema/flexible-array-init.c
index 99ef66abe9..909b856d17 100644
--- a/test/Sema/flexible-array-init.c
+++ b/test/Sema/flexible-array-init.c
@@ -1,4 +1,4 @@
-// RUN: clang -fsyntax-only -verify %s
+// RUN: clang -fsyntax-only -pedantic -verify %s
 struct one {
   int a;
   int values[];
@@ -12,17 +12,21 @@ void test() {
 
 struct foo { 
   int x; 
-  int y[]; // expected-note 3 {{initialized flexible array member 'y' is here}}
+  int y[]; // expected-note 4 {{initialized flexible array member 'y' is here}}
 }; 
-struct bar { struct foo z; };
+struct bar { struct foo z; }; // expected-warning {{'z' may not be nested in a struct due to flexible array member}}
      
 struct foo a = { 1, { 2, 3, 4 } };        // Valid.
 struct bar b = { { 1, { 2, 3, 4 } } };    // expected-error{{non-empty initialization of flexible array member inside subobject}}
-struct bar c = { { 1, { } } };            // Valid.
-struct foo d[1] = { { 1, { 2, 3, 4 } } };  // expected-error{{'struct foo' may not be used as an array element due to flexible array member}}
+struct bar c = { { 1, { } } };            // Valid. \
+              // expected-warning{{use of GNU empty initializer extension}} \
+              // expected-warning{{zero size arrays are an extension}}
+struct foo d[1] = { { 1, { 2, 3, 4 } } };  // expected-warning{{'struct foo' may not be used as an array element due to flexible array member}} \
+              // expected-error{{non-empty initialization of flexible array member inside subobject}}
 
 struct foo desig_foo = { .y = {2, 3, 4} };
-struct bar desig_bar = { .z.y = { } };
+struct bar desig_bar = { .z.y = { } }; // expected-warning{{use of GNU empty initializer extension}} \
+  // expected-warning{{zero size arrays are an extension}}
 struct bar desig_bar2 = { .z.y = { 2, 3, 4} }; // expected-error{{non-empty initialization of flexible array member inside subobject}}
 struct foo design_foo2 = { .y = 2 }; // expected-error{{flexible array requires brace-enclosed initializer}}
 
@@ -36,3 +40,19 @@ struct polygon {
 };
 struct polygon poly = { 
   .points[2] = { 1, 2} }; // expected-error{{designator into flexible array member subobject}}
+
+// PR3540
+struct X {
+  int a;
+  int b;
+  char data[];
+};
+
+struct Y {
+  int a:4;
+  int b:4;
+  int c;
+  int d;
+  int e;
+  struct X xs[]; // expected-warning{{'struct X' may not be used as an array element due to flexible array member}}
+};
-- 
2.40.0