[clang][modules] Detect invalidation of SDKSettings.json

Author: jansvoboda11

clang/include/clang/Serialization/ASTBitCodes.h

@@ -54,7 +54,7 @@ const unsigned VERSION_MAJOR = 34;
 /// for the previous version could still support reading the new
 /// version by ignoring new kinds of subblocks), this number
 /// should be increased.
-const unsigned VERSION_MINOR = 0;
+const unsigned VERSION_MINOR = 1;
 
 /// An ID number that refers to an identifier in an AST file.
 ///
@@ -386,6 +386,10 @@ enum ControlRecordTypes {
   /// Record code for the (optional) include-tree ID for implicit modules
   /// built with the dependency scanner.
   CAS_INCLUDE_TREE_ID,
+
+  /// Record code for the (optional) modification timestamp of the
+  /// SDKSettings.json file.
+  SDK_SETTINGS_JSON_TIMESTAMP,
 };
 
 /// Record types that occur within the options block inside

clang/lib/Serialization/ASTReader.cpp

@@ -3507,6 +3507,29 @@ ASTReader::ReadControlBlock(ModuleFile &F,
           return OutOfDate;
       }
       break;
+
+    case SDK_SETTINGS_JSON_TIMESTAMP: {
+      time_t ExpectedModTime = Record[0];
+      time_t ActualModTime = 0;
+      StringRef Sysroot =
+          PP.getHeaderSearchInfo().getHeaderSearchOpts().Sysroot;
+      if (!Sysroot.empty()) {
+        SmallString<128> SDKSettingsJSON = Sysroot;
+        llvm::sys::path::append(SDKSettingsJSON, "SDKSettings.json");
+        if (auto FE = PP.getFileManager().getOptionalFileRef(SDKSettingsJSON))
+          ActualModTime = FE->getModificationTime();
+      }
+      if (ActualModTime && ExpectedModTime &&
+          ActualModTime != ExpectedModTime) {
+        if (!canRecoverFromOutOfDate(F.FileName, ClientLoadCapabilities))
+          Diag(diag::err_fe_ast_file_modified)
+              << "SDKSettings.json" << moduleKindForDiagnostic(F.Kind)
+              << F.FileName << 1 << 1 << llvm::itostr(ExpectedModTime)
+              << llvm::itostr(ActualModTime);
+        return OutOfDate;
+      }
+      break;
+    }
     }
   }
 }

clang/lib/Serialization/ASTWriter.cpp

@@ -917,6 +917,7 @@ void ASTWriter::WriteBlockInfoBlock() {
   RECORD(MODULE_CACHE_KEY);
   RECORD(CASFS_ROOT_ID);
   RECORD(CAS_INCLUDE_TREE_ID);
+  RECORD(SDK_SETTINGS_JSON_TIMESTAMP);
 
   BLOCK(OPTIONS_BLOCK);
   RECORD(LANGUAGE_OPTIONS);
@@ -1615,6 +1616,20 @@ void ASTWriter::WriteControlBlock(Preprocessor &PP, StringRef isysroot) {
     Stream.EmitRecordWithBlob(AbbrevCode, Record, *ID);
   }
 
+  time_t SDKSettingsModTime = 0;
+  StringRef Sysroot = PP.getHeaderSearchInfo().getHeaderSearchOpts().Sysroot;
+  if (!Sysroot.empty()) {
+    SmallString<128> SDKSettingsJSON = Sysroot;
+    llvm::sys::path::append(SDKSettingsJSON, "SDKSettings.json");
+    if (auto FE = PP.getFileManager().getOptionalFileRef(SDKSettingsJSON))
+      SDKSettingsModTime = FE->getModificationTime();
+  }
+  if (SDKSettingsModTime) {
+    Record.clear();
+    Record.push_back(SDKSettingsModTime);
+    Stream.EmitRecord(SDK_SETTINGS_JSON_TIMESTAMP, Record);
+  }
+
   // Imports
   if (Chain) {
     auto Abbrev = std::make_shared<BitCodeAbbrev>();

clang/test/ClangScanDeps/modules-include-tree-sdk-settings.c

@@ -0,0 +1,37 @@
+// This test checks that the module cache gets invalidated when the
+// SDKSettings.json file changes. This prevents "file changed during build"
+// errors when the TU does get rescanned and recompiled.
+
+// REQUIRES: ondisk_cas
+
+// RUN: rm -rf %t
+// RUN: split-file %s %t
+
+//--- sdk/SDKSettings.json
+{
+  "Version": "11.0",
+  "MaximumDeploymentTarget": "11.0.99"
+}
+
+//--- module.modulemap
+module M { header "M.h" }
+//--- M.h
+//--- tu.c
+#include "M.h"
+
+// RUN: clang-scan-deps -format experimental-include-tree-full -cas-path %t/cas -o %t/deps_clean.json \
+// RUN:   -- %clang -target x86_64-apple-macos11 -isysroot %t/sdk \
+// RUN:      -c %t/tu.c -o %t/tu.o -fmodules -fmodules-cache-path=%t/cache
+
+// RUN: sleep 1
+// RUN: echo " " >> %t/sdk/SDKSettings.json
+// RUN: echo " " >> %t/tu.c
+
+// RUN: clang-scan-deps -format experimental-include-tree-full -cas-path %t/cas -o %t/deps_incremental.json \
+// RUN:   -- %clang -target x86_64-apple-macos11 -isysroot %t/sdk \
+// RUN:      -c %t/tu.c -o %t/tu.o -fmodules -fmodules-cache-path=%t/cache
+
+// RUN: %deps-to-rsp %t/deps_incremental.json --module-name M > %t/M.rsp
+// RUN: %deps-to-rsp %t/deps_incremental.json --tu-index 0 > %t/tu.rsp
+// RUN: %clang @%t/M.rsp
+// RUN: %clang @%t/tu.rsp