[DefiniteInitialization] Check whether globals captured by top-level defer statements are initialized.

include/swift/AST/DiagnosticsSIL.def

@@ -137,6 +137,9 @@ ERROR(variable_inout_before_initialized,none,
 ERROR(variable_closure_use_uninit,none,
       "%select{variable|constant}1 '%0' captured by a closure before being"
       " initialized", (StringRef, bool))
+ERROR(variable_defer_use_uninit,none,
+      "%select{variable|constant}1 '%0' used in defer before being"
+      " initialized", (StringRef, bool))
 ERROR(self_closure_use_uninit,none,
       "'self' captured by a closure before all members were initialized", ())
 

lib/SILGen/SILGenStmt.cpp

@@ -467,15 +467,22 @@ namespace {
 
 void StmtEmitter::visitDeferStmt(DeferStmt *S) {
   // Emit the closure for the defer, along with its binding.
-  SGF.visitFuncDecl(S->getTempDecl());
+  // If the defer is at the top-level code, insert 'mark_escape_inst'
+  // to the top-level code to check initialization of any captured globals.
+  FuncDecl *deferDecl = S->getTempDecl();
+  auto declCtxKind = deferDecl->getDeclContext()->getContextKind();
+  auto &sgm = SGF.SGM;
+  if (declCtxKind == DeclContextKind::TopLevelCodeDecl && sgm.TopLevelSGF &&
+      sgm.TopLevelSGF->B.hasValidInsertionPoint()) {
+    sgm.emitMarkFunctionEscapeForTopLevelCodeGlobals(
+        S, deferDecl->getCaptureInfo());
+  }
+  SGF.visitFuncDecl(deferDecl);
 
   // Register a cleanup to invoke the closure on any exit paths.
   SGF.Cleanups.pushCleanup<DeferCleanup>(S->getDeferLoc(), S->getCallExpr());
 }
 
-
-
-
 void StmtEmitter::visitIfStmt(IfStmt *S) {
   Scope condBufferScope(SGF.Cleanups, S);
 

lib/SILOptimizer/Mandatory/DefiniteInitialization.cpp

@@ -16,6 +16,7 @@
 #include "swift/AST/DiagnosticEngine.h"
 #include "swift/AST/DiagnosticsSIL.h"
 #include "swift/AST/Expr.h"
+#include "swift/AST/Stmt.h"
 #include "swift/ClangImporter/ClangModule.h"
 #include "swift/SIL/InstructionUtils.h"
 #include "swift/SIL/SILArgument.h"
@@ -1239,14 +1240,32 @@ void LifetimeChecker::handleEscapeUse(const DIMemoryUse &Use) {
     noteUninitializedMembers(Use);
     return;
   }
-
 
+  // Extract the reason why this escape-use instruction exists and present
+  // diagnostics. While an escape-use instruction generally corresponds to a
+  // capture by a closure, there are the following special cases to consider:
+  //
+  // (a) A MarkFunctionEscapeInst with an operand say %var. This is introduced
+  // by the SILGen phase when %var is the address of a global variable that
+  // escapes because it is used by a closure or a defer statement or a function
+  // definition appearing at the top-level. The specific reason why %var escapes
+  // is recorded in MarkFunctionEscapeInst by making its SIL Location refer to
+  // the AST of the construct that uses the global variable (namely, a closure
+  // or a defer statement or a function definition). So, if %var is
+  // uninitialized at MarkFunctionEscapeInst, extract and report the reason
+  // why the variable escapes in the error message.
+  //
+  // (b) An UncheckedTakeEnumDataAddrInst takes the address of the data of
+  // an optional and is introduced as an intermediate step in optional chaining.
   Diag<StringRef, bool> DiagMessage;
   if (isa<MarkFunctionEscapeInst>(Inst)) {
-    if (Inst->getLoc().isASTNode<AbstractClosureExpr>())
+    if (Inst->getLoc().isASTNode<AbstractClosureExpr>()) {
       DiagMessage = diag::variable_closure_use_uninit;
-    else
+    } else if (Inst->getLoc().isASTNode<DeferStmt>()) {
+      DiagMessage = diag::variable_defer_use_uninit;
+    } else {
       DiagMessage = diag::variable_function_use_uninit;
+    }
   } else if (isa<UncheckedTakeEnumDataAddrInst>(Inst)) {
     DiagMessage = diag::variable_used_before_initialized;
   } else {

test/SILGen/toplevel.swift

@@ -102,6 +102,17 @@ fooUsesUninitializedValue()
 NotInitializedInteger = 10
 fooUsesUninitializedValue()
 
+// Test initialization of variables captured by top-level defer.
+
+// CHECK: alloc_global @$S8toplevel9uninitVarSiv
+// CHECK-NEXT: [[UNINIADDR:%[0-9]+]] = global_addr @$S8toplevel9uninitVarSiv
+// CHECK-NEXT: [[UNINIMUI:%[0-9]+]] = mark_uninitialized [var] [[UNINIADDR]] : $*Int
+// CHECK-NEXT: mark_function_escape [[UNINIMUI]] : $*Int
+var uninitVar: Int
+defer {
+  print(uninitVar)
+}
+
 
 
 

test/SILOptimizer/definite_init_diagnostics_globals.swift

@@ -0,0 +1,86 @@
+// RUN: %target-swift-frontend -emit-sil -enable-sil-ownership -primary-file %s -o /dev/null -verify
+
+import Swift
+
+// Tests for definite initialization of globals.
+
+var x: Int         // expected-note {{variable defined here}}
+                   // expected-note@-1 {{variable defined here}}
+                   // expected-note@-2 {{variable defined here}}
+                   // expected-note@-3 {{variable defined here}}
+
+let y: Int         // expected-note {{constant defined here}}
+                   // expected-note@-1 {{constant defined here}}
+                   // expected-note@-2 {{constant defined here}}
+
+// Test top-level defer.
+defer { print(x) } // expected-error {{variable 'x' used in defer before being initialized}}
+
+defer { print(y) } // expected-error {{constant 'y' used in defer before being initialized}}
+
+// Test top-level functions.
+
+func testFunc() {       // expected-error {{variable 'x' used by function definition before being initialized}}
+  defer { print(x) }
+}
+
+// Test top-level closures.
+
+let clo: () -> Void = { print(y) } // expected-error {{constant 'y' captured by a closure before being initialized}}
+clo()
+
+({ () -> Void in print(x) })() // expected-error {{variable 'x' captured by a closure before being initialized}}
+
+let clo2: () -> Void = { [x] in print(x) } // expected-error {{variable 'x' used before being initialized}}
+clo2()
+
+class C {
+  var f = 0
+}
+
+var c: C  // expected-note {{variable defined here}}
+
+let clo3: () -> Void = { [weak c] in  // expected-error {{variable 'c' used before being initialized}}
+  guard let cref = c else{ return }
+  print(cref)
+}
+clo3()
+
+// Test inner functions.
+
+func testFunc2() {    // expected-error {{constant 'y' used by function definition before being initialized}}
+  func innerFunc() {
+    print(y)
+  }
+}
+
+// Test class initialization and methods.
+
+var w: String  // expected-note {{variable defined here}}
+               // expected-note@-1 {{variable defined here}}
+               // expected-note@-2 {{variable defined here}}
+
+// FIXME: the error should blame the class definition: <rdar://41490541>.
+class TestClass1 { // expected-error {{variable 'w' used by function definition before being initialized}}
+  let fld = w
+}
+
+class TestClass2 {
+  init() {        // expected-error {{variable 'w' used by function definition before being initialized}}
+    print(w)
+  }
+
+  func bar() {    // expected-error {{variable 'w' used by function definition before being initialized}}
+    print(w)
+  }
+}
+
+// Test initialization of global variables of protocol type.
+
+protocol P {
+  var f: Int { get }
+}
+
+var p: P    // expected-note {{variable defined here}}
+
+defer { print(p.f) } // expected-error {{variable 'p' used in defer before being initialized}}