base: let string accept multiple arguments

Issue #2064

repos/base/include/util/string.h

@@ -595,18 +595,6 @@ class Genode::String
 			}
 		};
 
-		template <typename... T>
-		void _init(T &&... args)
-		{
-			/* initialize string content */
-			Local_output output(_buf);
-			Genode::print(output, args...);
-
-			/* add terminating null */
-			_buf[output.num_chars()] = 0;
-			_len = output.num_chars() + 1;
-		}
-
 	public:
 
 		constexpr static size_t size() { return CAPACITY; }
@@ -616,6 +604,12 @@ class Genode::String
 		/**
 		 * Constructor
 		 *
+		 * The constructor accepts a non-zero number of arguments, which
+		 * are concatenated in the resulting 'String' object. In order to
+		 * generate the textual representation of the arguments, the
+		 * argument types must support the 'Output' interface, e.g., by
+		 * providing 'print' method.
+		 *
 		 * If the textual representation of the supplied arguments exceeds
 		 * 'CAPACITY', the resulting string gets truncated. The caller may
 		 * check for this condition by evaluating the 'length' of the
@@ -623,8 +617,17 @@ class Genode::String
 		 * may fit perfectly into the buffer or may have been truncated.
 		 * In general, it would be safe to assume the latter.
 		 */
-		template <typename T>
-		String(T const &arg) { _init(arg); }
+		template <typename T, typename... TAIL>
+		String(T const &arg, TAIL &&... args)
+		{
+			/* initialize string content */
+			Local_output output(_buf);
+			Genode::print(output, arg, args...);
+
+			/* add terminating null */
+			_buf[output.num_chars()] = 0;
+			_len = output.num_chars() + 1;
+		}
 
 		/**
 		 * Copy constructor

repos/base/run/log.run

@@ -32,5 +32,6 @@ compare_output_to {
 [init -> test-log] invalid hex range:  [f8,08) (overflow!)
 [init -> test-log] negative hex char:  0xfe
 [init -> test-log] positive hex char:  0x02
+[init -> test-log] multiarg string:    "parent -> child.7"
 [init -> test-log] Test done.
 }

repos/base/src/test/log/main.cc

@@ -26,5 +26,9 @@ void Component::construct(Genode::Env &env)
 	log("invalid hex range:  ", Hex_range<uint8_t>(0xf8, 0x10));
 	log("negative hex char:  ", Hex((char)-2LL, Hex::PREFIX, Hex::PAD));
 	log("positive hex char:  ", Hex((char) 2LL, Hex::PREFIX, Hex::PAD));
+
+	typedef String<128> Label;
+	log("multiarg string:    ", Label(Char('"'), "parent -> child.", 7, Char('"')));
+
 	log("Test done.");
 }