core: Avoid trivial snprintfs.

src/util.js.c

@@ -612,7 +612,7 @@ static int _tf_util_backtrace_single_callback(void* data, uintptr_t pc, const ch
 {
 	char** stack = data;
 	char line[256];
-	int length = snprintf(line, sizeof(line), "%s", function);
+	int length = (int)tf_string_set(line, sizeof(line), function);
 	int current = *stack ? strlen(*stack) : 0;
 	*stack = tf_resize_vec(*stack, current + length + 1);
 	memcpy(*stack + current, line, length + 1);
@@ -700,3 +700,18 @@ uint32_t tf_util_fnv32a(const void* buffer, int length, uint32_t start)
 	}
 	return result;
 }
+
+size_t tf_string_set(char* buffer, size_t size, const char* string)
+{
+	size_t length = string ? strlen(string) : 0;
+	length = tf_min(length, size - 1);
+	if (size)
+	{
+		if (length)
+		{
+			memcpy(buffer, string, length);
+		}
+		buffer[length] = 0;
+	}
+	return length;
+}