fix #13924: FP unknownMacro for C++ keyword in C code (danmar#7578)

Author: ludviggunne

lib/tokenize.cpp

@@ -8574,7 +8574,7 @@ void Tokenizer::findGarbageCode() const
             unknownMacroError(tok->linkAt(1)->previous());
 
         // UNKNOWN_MACRO(return)
-        else if (!tok->isKeyword() && Token::Match(tok, "%name% throw|return"))
+        else if (!tok->isKeyword() && (Token::Match(tok, "%name% return") || (isCPP() && Token::Match(tok, "%name% throw"))))
             unknownMacroError(tok);
 
         // Assign/increment/decrement literal

test/testtokenize.cpp

@@ -436,6 +436,8 @@ class TestTokenizer : public TestFixture {
 
         TEST_CASE(unknownMacroBeforeReturn);
 
+        TEST_CASE(cppKeywordInCSource);
+
         TEST_CASE(cppcast);
 
         TEST_CASE(checkHeader1);
@@ -7950,6 +7952,10 @@ class TestTokenizer : public TestFixture {
         ASSERT_THROW_INTERNAL(tokenizeAndStringify("int f() { X return 0; }"), UNKNOWN_MACRO);
     }
 
+    void cppKeywordInCSource() {
+        ASSERT_NO_THROW(tokenizeAndStringify("int throw() {}", true, Platform::Type::Native, false));
+    }
+
     void cppcast() {
         const char code[] = "a = const_cast<int>(x);\n"
                             "a = dynamic_cast<int>(x);\n"