[Sema] Suppress warnings for C's zero initializer

Patch by S. Gilles!

Differential Revision: https://reviews.llvm.org/D28148

llvm-svn: 314499

4 files changed, 61 insertions, 2 deletions

diff --git a/clang/include/clang/AST/Expr.h b/clang/include/clang/AST/Expr.h
index 219bd1e5fd9..bef2339e8e6 100644
--- a/clang/include/clang/AST/Expr.h
+++ b/clang/include/clang/AST/Expr.h
@@ -4011,6 +4011,10 @@ public:
   /// initializer)?
   bool isTransparent() const;
 
+  /// Is this the zero initializer {0} in a language which considers it
+  /// idiomatic?
+  bool isIdiomaticZeroInitializer(const LangOptions &LangOpts) const;
+
   SourceLocation getLBraceLoc() const { return LBraceLoc; }
   void setLBraceLoc(SourceLocation Loc) { LBraceLoc = Loc; }
   SourceLocation getRBraceLoc() const { return RBraceLoc; }
@@ -4020,6 +4024,9 @@ public:
   InitListExpr *getSemanticForm() const {
     return isSemanticForm() ? nullptr : AltForm.getPointer();
   }
+  bool isSyntacticForm() const {
+    return !AltForm.getInt() || !AltForm.getPointer();
+  }
   InitListExpr *getSyntacticForm() const {
     return isSemanticForm() ? AltForm.getPointer() : nullptr;
   }
diff --git a/clang/lib/AST/Expr.cpp b/clang/lib/AST/Expr.cpp
index aab89d392dc..9181176bbd9 100644
--- a/clang/lib/AST/Expr.cpp
+++ b/clang/lib/AST/Expr.cpp
@@ -1951,6 +1951,17 @@ bool InitListExpr::isTransparent() const {
          getInit(0)->getType().getCanonicalType();
 }
 
+bool InitListExpr::isIdiomaticZeroInitializer(const LangOptions &LangOpts) const {
+  assert(isSyntacticForm() && "only test syntactic form as zero initializer");
+
+  if (LangOpts.CPlusPlus || getNumInits() != 1) {
+    return false;
+  }
+
+  const IntegerLiteral *Lit = dyn_cast<IntegerLiteral>(getInit(0));
+  return Lit && Lit->getValue() == 0;
+}
+
 SourceLocation InitListExpr::getLocStart() const {
   if (InitListExpr *SyntacticForm = getSyntacticForm())
     return SyntacticForm->getLocStart();
diff --git a/clang/lib/Sema/SemaInit.cpp b/clang/lib/Sema/SemaInit.cpp
index 59ec9e28516..341e7120fe8 100644
--- a/clang/lib/Sema/SemaInit.cpp
+++ b/clang/lib/Sema/SemaInit.cpp
@@ -886,7 +886,8 @@ void InitListChecker::CheckImplicitInitList(const InitializedEntity &Entity,
     }
 
     // Complain about missing braces.
-    if (T->isArrayType() || T->isRecordType()) {
+    if ((T->isArrayType() || T->isRecordType()) &&
+        !ParentIList->isIdiomaticZeroInitializer(SemaRef.getLangOpts())) {
       SemaRef.Diag(StructuredSubobjectInitList->getLocStart(),
                    diag::warn_missing_braces)
           << StructuredSubobjectInitList->getSourceRange()
@@ -1833,7 +1834,9 @@ void InitListChecker::CheckStructUnionTypes(
   // worthwhile to skip over the rest of the initializer, though.
   RecordDecl *RD = DeclType->getAs<RecordType>()->getDecl();
   RecordDecl::field_iterator FieldEnd = RD->field_end();
-  bool CheckForMissingFields = true;
+  bool CheckForMissingFields =
+    !IList->isIdiomaticZeroInitializer(SemaRef.getLangOpts());
+
   while (Index < IList->getNumInits()) {
     Expr *Init = IList->getInit(Index);
 
diff --git a/clang/test/Sema/zero-initializer.c b/clang/test/Sema/zero-initializer.c
new file mode 100644
index 00000000000..472eed9517f
--- /dev/null
+++ b/clang/test/Sema/zero-initializer.c
@@ -0,0 +1,38 @@
+// RUN: %clang_cc1 -std=c99 -Wmissing-field-initializers -Wmissing-braces -verify %s
+
+// Tests that using {0} in struct initialization or assignment is supported
+struct foo { int x; int y; };
+struct bar { struct foo a; struct foo b; };
+struct A { int a; };
+struct B { struct A a; };
+struct C { struct B b; };
+
+int main(void)
+{
+  struct foo f = { 0 }; // no-warning
+  struct foo g = { 9 }; // expected-warning {{missing field 'y' initializer}}
+  struct foo h = { 9, 9 }; // no-warning
+  struct bar i = { 0 }; // no-warning
+  struct bar j = { 0, 0 }; // expected-warning {{suggest braces around initialization of subobject}} expected-warning {{missing field 'b' initializer}}
+  struct bar k = { { 9, 9 }, { 9, 9 } }; // no-warning
+  struct bar l = { { 9, 9 }, { 0 } }; // no-warning
+  struct bar m = { { 0 }, { 0 } }; // no-warning
+  struct bar n = { { 0 }, { 9, 9 } }; // no-warning
+  struct bar o = { { 9 }, { 9, 9 } }; // expected-warning {{missing field 'y' initializer}}
+  struct C p = { 0 }; // no-warning
+  struct C q = { 9 }; // expected-warning {{suggest braces around initialization of subobject}} expected-warning {{suggest braces around initialization of subobject}}
+  f = (struct foo ) { 0 }; // no-warning
+  g = (struct foo ) { 9 }; // expected-warning {{missing field 'y' initializer}}
+  h = (struct foo ) { 9, 9 }; // no-warning
+  i = (struct bar) { 0 }; // no-warning
+  j = (struct bar) { 0, 0 }; // expected-warning {{suggest braces around initialization of subobject}} expected-warning {{missing field 'b' initializer}}
+  k = (struct bar) { { 9, 9 }, { 9, 9 } }; // no-warning
+  l = (struct bar) { { 9, 9 }, { 0 } }; // no-warning
+  m = (struct bar) { { 0 }, { 0 } }; // no-warning
+  n = (struct bar) { { 0 }, { 9, 9 } }; // no-warning
+  o = (struct bar) { { 9 }, { 9, 9 } }; // expected-warning {{missing field 'y' initializer}}
+  p = (struct C) { 0 }; // no-warning
+  q = (struct C) { 9 }; // expected-warning {{suggest braces around initialization of subobject}} expected-warning {{suggest braces around initialization of subobject}}
+
+  return 0;
+}