C++: handle lesser and greater operators in template parameters

Close universal-ctags#769.

`<' and `>' operators can be used in parameters list of template
like:

    template<char i, bool B = (i>0)>     void f0(void) { }
    template<char i, bool B = i < 10>    void f1(void) { }

ctags could not handle them well.

This commit tries to improve the way to handle them.

The original checks only the balance of angle brackets.
In addition the original way, this commit considers
following things when checking the balance of angle
brackets:

1. lesser and greater operators between rounded brackets are ignored.

2. When `=' is found, lesser and greater operators are
   ignore till the input satisfies one of following conditions:
   2.1 `,' is found outside rounded brackets, or
   2.2 `>' is found outside rounded brackets,

Signed-off-by: Masatake YAMATO <[email protected]>

Author: masatake

Units/parser-cpp.r/less-than-operator-between-anglebrackets.d/args.ctags

@@ -0,0 +1 @@
+--sort=no

Units/parser-cpp.r/less-than-operator-between-anglebrackets.d/expected.tags

@@ -0,0 +1,13 @@
+f0	input.cpp	/^template<char i, bool B = (i>0)>     void f0(void) { }$/;"	f
+f1	input.cpp	/^template<char i, bool B = i < 10>    void f1(void) { }$/;"	f
+f2	input.cpp	/^template<char i, long j = (i << 10)> void f2(void) { }$/;"	f
+f3	input.cpp	/^template<char i, long j = i << 10>   void f3(void) { }$/;"	f
+f4	input.cpp	/^template<char i, long j = (i >> 10)> void f4(void) { }$/;"	f
+f5	input.cpp	/^template<char i, long j = (i > 10)>  void f5(void) { }$/;"	f
+f6	input.cpp	/^template<char i, bool B = (i <= 10)> void f6(void) { }$/;"	f
+f7	input.cpp	/^template<char i, bool B = (i >= 10)> void f7(void) { }$/;"	f
+f8	input.cpp	/^template<char i, char j, bool B = i < 10 && (30 > j)> void f8(void) { }$/;"	f
+f9	input.cpp	/^template<char i, char j, bool B = i < (10 && 30 > j)> void f9(void) { }$/;"	f
+f10	input.cpp	/^template<char i, char j, bool B = (i < 10 && 30 > j)> void f10(void) { }$/;"	f
+f11	input.cpp	/^template<bool b = 0 < 2 && 2 < 4> void f11(void) { }$/;"	f
+main	input.cpp	/^int main(void) { return 0; }$/;"	f

Units/parser-cpp.r/less-than-operator-between-anglebrackets.d/input.cpp

@@ -0,0 +1,16 @@
+/* "gcc input.cpp -c -std=c++11" accepts this source code. */
+
+template<char i, bool B = (i>0)>     void f0(void) { }
+template<char i, bool B = i < 10>    void f1(void) { }
+template<char i, long j = (i << 10)> void f2(void) { }
+template<char i, long j = i << 10>   void f3(void) { }
+template<char i, long j = (i >> 10)> void f4(void) { }
+template<char i, long j = (i > 10)>  void f5(void) { }
+template<char i, bool B = (i <= 10)> void f6(void) { }
+template<char i, bool B = (i >= 10)> void f7(void) { }
+template<char i, char j, bool B = i < 10 && (30 > j)> void f8(void) { }
+template<char i, char j, bool B = i < (10 && 30 > j)> void f9(void) { }
+template<char i, char j, bool B = (i < 10 && 30 > j)> void f10(void) { }
+template<bool b = 0 < 2 && 2 < 4> void f11(void) { }
+template<typename T1, typename T2> class A;
+int main(void) { return 0; }

parsers/c.c

@@ -1761,6 +1761,54 @@ static void skipToMatch (const char *const pair)
 	}
 }
 
+static void skipCppTemplateParameterList (void)
+{
+	const unsigned long inputLineNumber = getInputLineNumber ();
+	int angleBracketsLevel = 1;
+	int c = '\0';
+
+	int roundBracketsLevel = 0;
+	boolean defaultValueExpected = FALSE;
+
+	while (angleBracketsLevel > 0  &&  (c = skipToNonWhite ()) != EOF)
+	{
+		if (CollectingSignature)
+			vStringPut (Signature, c);
+
+		if (c == '<')
+		{
+			if (roundBracketsLevel == 0)
+			{
+				if (defaultValueExpected == FALSE)
+					++angleBracketsLevel;
+			}
+		}
+		else if (c == '>')
+		{
+			if (roundBracketsLevel == 0)
+			{
+				--angleBracketsLevel;
+				defaultValueExpected = FALSE;
+			}
+		}
+		else if (c == '(')
+			roundBracketsLevel ++;
+		else if (c == ')')
+			roundBracketsLevel --;
+		else if (c == '=' && (roundBracketsLevel == 0))
+			defaultValueExpected = TRUE;
+		else if (c == ',' && (roundBracketsLevel == 0))
+			defaultValueExpected = FALSE;
+	}
+
+	if (c == EOF)
+	{
+		verbose ("%s: failed to find match for '%c' at line %lu\n",
+				getInputFileName (), '<', inputLineNumber);
+		longjmp (Exception, (int) ExceptionFormattingError);
+	}
+}
+
 static void skipParens (void)
 {
 	const int c = skipToNonWhite ();
@@ -2523,7 +2571,10 @@ static void processAngleBracket (void)
 	} else if (languageSupportsGenerics () && c != '<' && c != '=') {
 		/* this is a template */
 		cppUngetc (c);
-		skipToMatch ("<>");
+		if (isInputLanguage (Lang_cpp))
+			skipCppTemplateParameterList ();
+		else
+			skipToMatch ("<>");
 	} else if (c == '<') {
 		/* skip "<<" or "<<=". */
 		c = cppGetc ();