Merge pull request #23076 from adrian-prantl/48509051

 Stop producing line and file debug information for clang::Decls.

Author: adrian-prantl

lib/IRGen/IRGenDebugInfo.cpp

@@ -240,14 +240,14 @@ class IRGenDebugInfoImpl : public IRGenDebugInfo {
     if (!D)
       return L;
 
-    if (auto *ClangDecl = D->getClangDecl()) {
-      auto ClangSrcLoc = ClangDecl->getBeginLoc();
-      clang::SourceManager &ClangSM =
-          CI.getClangASTContext().getSourceManager();
-      L.Line = ClangSM.getPresumedLineNumber(ClangSrcLoc);
-      L.Filename = ClangSM.getBufferName(ClangSrcLoc);
-      return L;
-    }
+    // If D is a clang::Decl, it would be nice to query the clang::SourceManager
+    // for the source location of the clang::Decl here, but module out-of-date
+    // rebuilds may unload previously loaded clang::Modules and thus also
+    // invalidate source locations pointed to, leading to a use-after-free
+    // here. If this functionality is desired, the source location must be
+    // captured by ClangImporter and stored on the side.
+    // LLDB only uses the DW_AT_decl_file / DW_AT_decl_line for C++ types.
+
     return getSwiftDebugLoc(DI, D, End);
   }
 

test/ClangImporter/objc_ir.swift

@@ -360,10 +360,11 @@ func testBlocksWithGenerics(hba: HasBlockArray) -> Any {
 // CHECK: attributes [[NOUNWIND]] = { nounwind }
 
 // CHECK: ![[SWIFT_NAME_ALIAS_VAR]] = !DILocalVariable(name: "obj", arg: 1, scope: !{{[0-9]+}}, file: !{{[0-9]+}}, line: {{[0-9]+}}, type: ![[SWIFT_NAME_ALIAS_TYPE:[0-9]+]])
-// CHECK: ![[SWIFT_NAME_ALIAS_TYPE]] = !DIDerivedType(tag: DW_TAG_typedef, name: "$sSo14SwiftNameAliasaD", scope: !{{[0-9]+}}, file: !{{[0-9]+}}, line: {{[0-9]+}}, baseType: !{{[0-9]+}})
+// CHECK: ![[SWIFT_NAME_ALIAS_TYPE]] = !DIDerivedType(tag: DW_TAG_typedef, name: "$sSo14SwiftNameAliasaD", scope: !{{[0-9]+}}, file: !{{[0-9]+}}, baseType: !{{[0-9]+}})
 
 // CHECK: ![[SWIFT_GENERIC_NAME_ALIAS_VAR]] = !DILocalVariable(name: "generic_obj", arg: 1, scope: !{{[0-9]+}}, file: !{{[0-9]+}}, line: {{[0-9]+}}, type: ![[SWIFT_GENERIC_NAME_ALIAS_TYPE:[0-9]+]])
-// CHECK: ![[SWIFT_GENERIC_NAME_ALIAS_TYPE]] = !DIDerivedType(tag: DW_TAG_typedef, name: "$sSo21SwiftGenericNameAliasaySo8NSNumberCGD", scope: !{{[0-9]+}}, file: !{{[0-9]+}}, line: {{[0-9]+}}, baseType: !{{[0-9]+}})
+// CHECK: ![[SWIFT_GENERIC_NAME_ALIAS_TYPE]] = !DIDerivedType(tag: DW_TAG_typedef, name: "$sSo21SwiftGenericNameAliasaySo8NSNumberCGD", scope: !{{[0-9]+}}, file: !{{[0-9]+}}, baseType: !{{[0-9]+}})
 
 // CHECK: ![[SWIFT_CONSTR_GENERIC_NAME_ALIAS_VAR]] = !DILocalVariable(name: "constr_generic_obj", arg: 1, scope: !{{[0-9]+}}, file: !{{[0-9]+}}, line: {{[0-9]+}}, type: ![[SWIFT_CONSTR_GENERIC_NAME_ALIAS_TYPE:[0-9]+]])
-// CHECK: ![[SWIFT_CONSTR_GENERIC_NAME_ALIAS_TYPE]] = !DIDerivedType(tag: DW_TAG_typedef, name: "$sSo27SwiftConstrGenericNameAliasaySo8NSNumberCGD", scope: !{{[0-9]+}}, file: !{{[0-9]+}}, line: {{[0-9]+}}, baseType: !{{[0-9]+}})
+// CHECK: ![[SWIFT_CONSTR_GENERIC_NAME_ALIAS_TYPE]] = !DIDerivedType(tag: DW_TAG_typedef, name: "$sSo27SwiftConstrGenericNameAliasaySo8NSNumberCGD", scope: !{{[0-9]+}}, file: !{{[0-9]+}}, baseType: !{{[0-9]+}})
+