[Caching] Fix stack-use-after-scope in CachedDiagnostics

Fix a stack-use-after-scope in the CachedDiagnostics when the
DiagnosticInfo entry that is getting deserialized has ChildDiagnostics.

There are some fields in the DiagnosticInfo are not owned by the
DiagnosticsInfo itself. While the callback during the deserialization
ensures those fields are still alive for the top level DiagnosticInfo
when it gets used, it is not true for any child diagnostics info inside.

rdar://123846525

Author: cachemeifyoucan

lib/Frontend/CachedDiagnostics.cpp

@@ -159,8 +159,14 @@ struct DiagnosticSerializer {
   llvm::Expected<DiagnosticInfo::FixIt>
   deserializeFixIt(const SerializedFixIt &);
 
+  // Stores the temporary data from deserialization.
+  struct DiagnosticStorage {
+    SmallVector<DiagnosticInfo, 2> ChildDiag;
+    SmallVector<CharSourceRange, 2> Ranges;
+    SmallVector<DiagnosticInfo::FixIt, 2> FixIts;
+  };
   llvm::Error deserializeDiagnosticInfo(const SerializedDiagnosticInfo &,
-                                        ReplayFunc);
+                                        DiagnosticStorage &, ReplayFunc);
 
   // Deserialize File and return the bufferID in serializing SourceManager.
   unsigned deserializeFile(const SerializedFile &File);
@@ -288,8 +294,10 @@ void DiagnosticSerializer::handleDiagnostic(SourceManager &SM,
                                             const DiagnosticInfo &Info,
                                             ReplayFunc Fn) {
   DiagInfos.emplace_back(convertDiagnosticInfo(SM, Info));
-  if (Fn)
-    cantFail(deserializeDiagnosticInfo(DiagInfos.back(), Fn));
+  if (Fn) {
+    DiagnosticStorage Storage;
+    cantFail(deserializeDiagnosticInfo(DiagInfos.back(), Storage, Fn));
+  }
 }
 
 unsigned DiagnosticSerializer::getFileIDFromBufferID(SourceManager &SM,
@@ -537,7 +545,8 @@ llvm::Error DiagnosticSerializer::deserializeGeneratedFileInfo(
 }
 
 llvm::Error DiagnosticSerializer::deserializeDiagnosticInfo(
-    const SerializedDiagnosticInfo &Info, ReplayFunc callback) {
+    const SerializedDiagnosticInfo &Info, DiagnosticStorage &Storage,
+    ReplayFunc callback) {
   DiagID ID = (DiagID)Info.ID;
   auto Loc = deserializeSourceLoc(Info.Loc);
   if (!Loc)
@@ -546,33 +555,32 @@ llvm::Error DiagnosticSerializer::deserializeDiagnosticInfo(
   auto BICD = deserializeSourceLoc(Info.BufferIndirectlyCausingDiagnostic);
   if (!BICD)
     return BICD.takeError();
-  SmallVector<DiagnosticInfo, 2> ChildDiag;
+
+  llvm::TinyPtrVector<DiagnosticInfo *> ChildDiagPtrs;
   for (auto &CD : Info.ChildDiagnosticInfo) {
-    auto E = deserializeDiagnosticInfo(CD, [&](const DiagnosticInfo &Info) {
-      ChildDiag.emplace_back(Info);
-      return llvm::Error::success();
-    });
+    auto E =
+        deserializeDiagnosticInfo(CD, Storage, [&](const DiagnosticInfo &Info) {
+          Storage.ChildDiag.emplace_back(Info);
+          ChildDiagPtrs.push_back(&Storage.ChildDiag.back());
+          return llvm::Error::success();
+        });
     if (E)
       return E;
   }
-  llvm::TinyPtrVector<DiagnosticInfo*> ChildDiagPtrs;
-  llvm::for_each(ChildDiag, [&ChildDiagPtrs](DiagnosticInfo &I) {
-    ChildDiagPtrs.push_back(&I);
-  });
-  SmallVector<CharSourceRange, 2> Ranges;
   for (auto &R : Info.Ranges) {
     auto Range = deserializeSourceRange(R);
     if (!Range)
       return Range.takeError();
-    Ranges.emplace_back(*Range);
+    Storage.Ranges.emplace_back(*Range);
   }
-  SmallVector<DiagnosticInfo::FixIt, 2> FixIts;
+  auto Ranges = ArrayRef(Storage.Ranges).take_back(Info.Ranges.size());
   for (auto &F : Info.FixIts) {
     auto FixIt = deserializeFixIt(F);
     if (!FixIt)
       return FixIt.takeError();
-    FixIts.emplace_back(*FixIt);
+    Storage.FixIts.emplace_back(*FixIt);
   }
+  auto FixIts = ArrayRef(Storage.FixIts).take_back(Info.FixIts.size());
 
   DiagnosticInfo DeserializedInfo{ID,
                                   *Loc,
@@ -623,11 +631,13 @@ llvm::Error DiagnosticSerializer::doEmitFromCached(llvm::StringRef Buffer,
   }
 
   for (auto &Info : DiagInfos) {
-    auto E = deserializeDiagnosticInfo(Info, [&](const DiagnosticInfo &Info) {
-      for (auto *Diag : Diags.getConsumers())
-        Diag->handleDiagnostic(SrcMgr, Info);
-      return llvm::Error::success();
-    });
+    DiagnosticStorage Storage;
+    auto E = deserializeDiagnosticInfo(Info, Storage,
+                                       [&](const DiagnosticInfo &Info) {
+                                         for (auto *Diag : Diags.getConsumers())
+                                           Diag->handleDiagnostic(SrcMgr, Info);
+                                         return llvm::Error::success();
+                                       });
     if (E)
       return E;
   }

test/CAS/cached_diagnostics.swift

@@ -4,24 +4,33 @@
 // RUN: %empty-directory(%t)
 
 // RUN: %target-swift-frontend -scan-dependencies -module-name Test -O -import-objc-header %S/Inputs/objc.h \
-// RUN:   -disable-implicit-string-processing-module-import -disable-implicit-concurrency-module-import -parse-stdlib \
+// RUN:   -disable-implicit-string-processing-module-import -disable-implicit-concurrency-module-import \
 // RUN:   %s -o %t/deps.json -cache-compile-job -cas-path %t/cas
 
+// RUN: %{python} %S/Inputs/BuildCommandExtractor.py %t/deps.json clang:SwiftShims > %t/shim.cmd
+// RUN: %swift_frontend_plain @%t/shim.cmd
+// RUN: %{python} %S/Inputs/BuildCommandExtractor.py %t/deps.json Swift > %t/swift.cmd
+// RUN: %swift_frontend_plain @%t/swift.cmd
+
 // RUN: %{python} %S/Inputs/BuildCommandExtractor.py %t/deps.json bridgingHeader | tail -n +2  > %t/header.cmd
 // RUN: %target-swift-frontend @%t/header.cmd -disable-implicit-swift-modules %S/Inputs/objc.h -O -o %t/objc.pch 2>&1 | %FileCheck %s -check-prefix CHECK-BRIDGE
 // RUN: %cache-tool -cas-path %t/cas -cache-tool-action print-output-keys -- \
 // RUN:   %target-swift-frontend @%t/header.cmd -disable-implicit-swift-modules %S/Inputs/objc.h -O -o %t/objc.pch > %t/keys.json
 // RUN: %{python} %S/Inputs/ExtractOutputKey.py %t/keys.json %S/Inputs/objc.h > %t/key
 
+// RUN: %{python} %S/Inputs/GenerateExplicitModuleMap.py %t/deps.json > %t/map.json
+// RUN: llvm-cas --cas %t/cas --make-blob --data %t/map.json > %t/map.casid
+
 // RUN: %{python} %S/Inputs/BuildCommandExtractor.py %t/deps.json Test > %t/MyApp.cmd
 // RUN: echo "\"-disable-implicit-string-processing-module-import\"" >> %t/MyApp.cmd
 // RUN: echo "\"-disable-implicit-concurrency-module-import\"" >> %t/MyApp.cmd
 // RUN: echo "\"-disable-implicit-swift-modules\"" >> %t/MyApp.cmd
-// RUN: echo "\"-parse-stdlib\"" >> %t/MyApp.cmd
 // RUN: echo "\"-import-objc-header\"" >> %t/MyApp.cmd
 // RUN: echo "\"%t/objc.pch\"" >> %t/MyApp.cmd
 // RUN: echo "\"-bridging-header-pch-key\"" >> %t/MyApp.cmd
 // RUN: echo "\"@%t/key\"" >> %t/MyApp.cmd
+// RUN: echo "\"-explicit-swift-module-map-file\"" >> %t/MyApp.cmd
+// RUN: echo "\"@%t/map.casid\"" >> %t/MyApp.cmd
 
 // RUN: %target-swift-frontend  -cache-compile-job -module-name Test -O -cas-path %t/cas @%t/MyApp.cmd %s \
 // RUN:   -emit-module -o %t/test.swiftmodule 2>&1 | %FileCheck %s
@@ -32,6 +41,15 @@
 
 #warning("this is a warning")  // expected-warning {{this is a warning}}
 
+enum MyEnum {
+    case kind
+    case none
+}
+
+let _ : MyEnum? = .none // expected-warning {{assuming you mean 'Optional<MyEnum>.none'; did you mean 'MyEnum.none' instead?}}
+// expected-note@-1 {{explicitly specify 'Optional' to silence this warning}} {{19-19=Optional}}
+// expected-note@-2 {{use 'MyEnum.none' instead}} {{19-19=MyEnum}}
+
 // CHECK-BRIDGE: warning: warning in bridging header
 // CHECK: warning: this is a warning