fixed #13687 - avoid null pointer dereference with incomplete remark comment (danmar#7370)

Author: firewave

lib/preprocessor.cpp

@@ -168,6 +168,8 @@ static bool parseInlineSuppressionCommentToken(const simplecpp::Token *tok, std:
 }
 
 static std::string getRelativeFilename(const simplecpp::Token* tok, const Settings &settings) {
+    if (!tok)
+        return "";
     std::string relativeFilename(tok->location.file());
     if (settings.relativePaths) {
         for (const std::string & basePath : settings.basePaths) {
@@ -1079,6 +1081,8 @@ void Preprocessor::addRemarkComments(const simplecpp::TokenList &tokens, std::ve
                 remarkedToken = prev;
             break;
         }
+        if (!remarkedToken)
+            continue;
 
         // Relative filename
         const std::string relativeFilename = getRelativeFilename(remarkedToken, mSettings);

test/cli/fuzz-crash/crash-2cf8ffd04628a7c025bb07074462a51c1284dff0

@@ -0,0 +1 @@
+//REMARK /

test/testpreprocessor.cpp

@@ -195,6 +195,7 @@ class TestPreprocessor : public TestFixture {
         TEST_CASE(remarkComment1);
         TEST_CASE(remarkComment2);
         TEST_CASE(remarkComment3);
+        TEST_CASE(remarkComment4);
 
         // Using -D to predefine symbols
         TEST_CASE(predefine1);
@@ -1940,6 +1941,12 @@ class TestPreprocessor : public TestFixture {
         ASSERT_EQUALS("assignment with 1 ", remarkComments[0].str);
     }
 
+    void remarkComment4() {
+        const char code[] = "//REMARK /";
+        const auto remarkComments = PreprocessorHelper::getRemarkComments(code, *this);
+        ASSERT_EQUALS(0, remarkComments.size());
+    }
+
     void predefine1() {
         const std::string src("#if defined X || Y\n"
                               "Fred & Wilma\n"