C++: Fix MSVC assert in std::isspace()

...when dealing with UTF8 bytes.

std::isspace() expects unsigned char, not char.

Change-Id: I3f9b5e347d79cf94015cc99f8797d5feab406151
Reviewed-by: Orgad Shaneh <orgads@gmail.com>
Reviewed-by: Marco Bubke <marco.bubke@theqtcompany.com>

src/libs/cplusplus/pp-engine.cpp

@@ -2129,7 +2129,7 @@ void Preprocessor::maybeStartOutputLine()
     // If previous line ends with \ (possibly followed by whitespace), add another \n
     const char *start = buffer.constData();
     const char *ch = start + buffer.length() - 2;
-    while (ch > start && (*ch != '\n') && std::isspace(*ch))
+    while (ch > start && (*ch != '\n') && pp_isspace(*ch))
         --ch;
     if (*ch == '\\')
         buffer.append('\n');

tests/auto/cplusplus/preprocessor/tst_preprocessor.cpp

@@ -409,6 +409,7 @@ private slots:
     void undef();
     void concat();
     void excessive_nesting();
+    void multi_byte_code_point_in_expansion();
 };
 
 // Remove all #... lines, and 'simplify' string, to allow easily comparing the result
@@ -2064,6 +2065,26 @@ void tst_Preprocessor::excessive_nesting()
     QCOMPARE(prep, output);
 }
 
+void tst_Preprocessor::multi_byte_code_point_in_expansion()
+{
+    Environment env;
+    Preprocessor preprocess(0, &env);
+    const QByteArray input =
+        "#define FOO(x) x\n"
+        "FOO(arg" UC_U00FC "\n)\n";
+
+    const QByteArray actual = preprocess.run(QLatin1String("<stdin>"), input);
+
+    const QByteArray expected =
+        "# 1 \"<stdin>\"\n"
+        "\n"
+        "# expansion begin 17,3 2:4\n"
+        "arg" UC_U00FC "\n"
+        "# expansion end\n"
+        "# 4 \"<stdin>\"\n";
+    QCOMPARE(actual, expected);
+}
+
 void tst_Preprocessor::compare_input_output(bool keepComments)
 {
     QFETCH(QByteArray, input);