I met this error when compiling an open source project:
/usr/local/include/dbus-1.0/dbus/dbus-protocol.h:459:126: error: invalid suffix on literal; C++11 requires a space between literal and identifier [-Wreserved-user-defined-literal]
#define DBUS_INTROSPECT_1_0_XML_DOCTYPE_DECL_NODE "<!DOCTYPE node PUBLIC \""DBUS_INTROSPECT_1_0_XML_PUBLIC_IDENTIFIER"\"\n\""DBUS_INTROSPECT_1_0_XML_SYSTEM_IDENTIFIER"\">\n"
This is fixed by changing the above macro definition:
-#define DBUS_INTROSPECT_1_0_XML_DOCTYPE_DECL_NODE "<!DOCTYPE node PUBLIC \""DBUS_INTROSPECT_1_0_XML_PUBLIC_IDENTIFIER"\"\n\""DBUS_INTROSPECT_1_0_XML_SYSTEM_IDENTIFIER"\">\n"
+#define DBUS_INTROSPECT_1_0_XML_DOCTYPE_DECL_NODE "<!DOCTYPE node PUBLIC \"" DBUS_INTROSPECT_1_0_XML_PUBLIC_IDENTIFIER "\"\n\"" DBUS_INTROSPECT_1_0_XML_SYSTEM_IDENTIFIER "\">\n
What confused me is the #define itself:
#define A "" B "" C ""
What is this?
We can use #define like this?
You can use #define to define a macro that contains anything.
Whether or not this results in valid C++ code that can be compiled, when the macro gets used, is an entirely different story.