[ClangScanDeps] Avoid use-of-uninitialized-memory for end-of-directive edge case

clang/lib/Lex/PPDirectives.cpp

@@ -466,6 +466,9 @@ SourceLocation
 Preprocessor::CheckEndOfDirective(StringRef DirType, bool EnableMacros,
                                   SmallVectorImpl<Token> *ExtraToks) {
   Token Tmp;
+  // Avoid use-of-uninitialized-memory for edge case(s) where there is no extra
+  // token to be parsed.
+  Tmp.startToken();
   auto ReadNextTok = [this, ExtraToks, &Tmp](auto &&LexFn) {
     std::invoke(LexFn, this, Tmp);
     if (ExtraToks && Tmp.isNot(tok::eod))

clang/test/ClangScanDeps/p1689-suppress-warnings-no-eol.cppm

@@ -0,0 +1,25 @@
+// Test that there is no use-of-uninitialized memory when parsing '#include' in
+// the last line, without a newline.
+//
+// Forked from p1689-suppress-warnings.cppm.
+
+// RUN: rm -rf %t
+// RUN: mkdir -p %t
+// RUN: split-file %s %t
+
+// Test P1689 format - should NOT emit warnings
+// RUN: clang-scan-deps -format=p1689 -- %clang++ -std=c++20 -I%t -c %t/mylib.cppm -o %t/mylib.o 2>&1 | FileCheck %s
+
+// CHECK-NOT: warning:
+// CHECK: {
+// CHECK: "revision"
+
+//--- header.h
+// Empty header for testing
+
+//--- mylib.cppm
+module;
+
+export module mylib;
+
+#include <header.h>