Multi-line macro defining another set of macros - c++

Question

In my project I have very many files and I want to manage debug with C++ macros. For every file, I want to use its own switch for enable or disable debug and adjust debug level. So basically there is shared file with settings:
This is how shared file debug.h looks:
#define DEBUG_LEVEL_LOG -1
#define DEBUG_LEVEL_NONE 0
#define DEBUG_LEVEL_ERROR 1
#define DEBUG_LEVEL_WARNING 2
#define DEBUG_LEVEL_INFO 3
#define DEBUG_LEVEL_DEBUG 4
#define DEBUG_LEVEL_TRACE 5
#ifndef ON
#define ON 1
#endif
#ifndef OFF
#define OFF 0
#endif
// setings for component "wireless"
#define WIRELESS_DEBUGGING ON
#define WIRELESS_DEBUGGING_LEVEL DEBUG_LEVEL_ERROR
// settings for another components
...
In every file I want to debug with this settings I need to define another bunch of macros. For example file "wireless.h"
#ifndef WIRELESS_DEBUGGING
#define WIRELESS_DEBUGGING_LEVEL DEBUG_LEVEL_NONE
#endif
#if WIRELESS_DEBUGGING
#if WIRELESS_DEBUGGING_LEVEL >= DEBUG_LEVEL_LOG
#define WIRELESS_LOG(...); Logger::log(__VA_ARGS__);
#else
#define WIRELESS_LOG(...); {}
#endif
#if WIRELESS_DEBUGGING_LEVEL >= DEBUG_LEVEL_ERROR
#define WIRELESS_ERROR(...); Logger::error(__VA_ARGS__);
#else
#define WIRELESS_ERROR(...); {}
#endif
#if WIRELESS_DEBUGGING_LEVEL >= DEBUG_LEVEL_WARNING
#define WIRELESS_WARNING(...); Logger::warning(__VA_ARGS__);
#else
#define WIRELESS_WARNING(...); {}
#endif
#if WIRELESS_DEBUGGING_LEVEL >= DEBUG_LEVEL_INFO
#define WIRELESS_INFO(...); Logger::info(__VA_ARGS__);
#else
#define WIRELESS_INFO(...); {}
#endif
#if WIRELESS_DEBUGGING_LEVEL >= DEBUG_LEVEL_DEBUG
#define WIRELESS_DEBUG(...); Logger::debug(__VA_ARGS__);
#else
#define WIRELESS_DEBUG(...); {}
#endif
#if WIRELESS_DEBUGGING_LEVEL >= DEBUG_LEVEL_TRACE
#define WIRELESS_TRACE(...); Logger::trace(__VA_ARGS__);
#else
#define WIRELESS_TRACE(...); {}
#endif
#else
#define WIRELESS_LOG(...); {}
#define WIRELESS_ERROR(...); {}
#define WIRELESS_WARNING(...); {}
#define WIRELESS_INFO(...); {}
#define WIRELESS_DEBUG(...); {}
#define WIRELESS_TRACE(...); {}
#endif
When I want to debug given component, I simply use something like this (in wireless.cpp)
WIRELESS_TRACE("wireless: hello world\n");
... etc ...
So far it's working. And here is the question: I don't want to use "local" bunch of definitions similar to definitions in file "wireless.h" in every component I'm using only with different prefix. Instead of this I want to have some "super macro" which will look similar to this
REGISTER_DEBUG(WIRELESS);
Is there a way how to achieve this using some concatenation and multi-line macro? I have found that using #define inside #define is forbidden.

Answer 1

I'm not completely sure what you want, so if this doesn't fit let me know and I'll delete.
There is the possibility of concatenating tokens in the preprocessor using ##. See, for example, https://gcc.gnu.org/onlinedocs/cpp/Concatenation.html

Answer 2

This is somewhat clumsy, but should do the trick:
#define DEBUG_LEVEL_LOG -1
#define DEBUG_LEVEL_NONE 0
#define DEBUG_LEVEL_ERROR 1
#define DEBUG_LEVEL_WARNING 2
#define DEBUG_LEVEL_INFO 3
#define DEBUG_LEVEL_DEBUG 4
#define DEBUG_LEVEL_TRACE 5
#define TRACE(a,...) _TRACE(a,__VA_ARGS__)
#define _TRACE(a,...) __TRACE_##a(__VA_ARGS__)
#define __TRACE_5(...) do{Logger::trace(__VA_ARGS__);}while(0)
Here is the clumsiness: you also need to define __TRACE_4, __TRACE_3 and so on to be empty. And then you need to define the same thing for Debug:
#define __DEBUG_4(...) do{Logger::debug(__VA_ARGS__);}while(0)
But in the end, after you defined your Wireless log level:
#define WIRELESS_LEVEL 5
you can just call the macro just like this:
TRACE(WIRELESS_LEVEL,"wireless: hello world\n");
Edit
Alternatively (this might be cleaner):
#define __PRINT_55(...) do{Logger::trace(__VA_ARGS__);}while(0)
#define __PRINT_44(...) do{Logger::debug(__VA_ARGS__);}while(0)
// etc...
// Also need to define what you need to be not printed:
#define __PRINT_01(...)
// etc...
#define PRINT(a,b,...) _PRINT(a,b,__VA_ARGS__)
#define _PRINT(a,b,...) __PRINT_##a##b(__VA_ARGS__)
Now you can call your function like this:
PRINT(DEBUG_LEVEL_TRACE, WIRELESS_LEVEL, "Hello world\n");

Answer 3

You can get there by switching from macros to inline functions. Something like this:
// debug.h
enum DebugLevel {
DEBUG_LEVEL_LOG = -1,
DEBUG_LEVEL_NONE = 0,
DEBUG_LEVEL_ERROR = 1,
DEBUG_LEVEL_WARNING = 2,
DEBUG_LEVEL_INFO = 3,
DEBUG_LEVEL_DEBUG = 4,
DEBUG_LEVEL_TRACE = 5
};
// settings for component "wireless"
constexpr bool WIRELESS_DEBUGGING = true;
constexpr DebugLevel WIRELESS_DEBUGGING_LEVEL = DEBUG_LEVEL_ERROR;
#define REGISTER_DEBUG_FUNC(topic, level, func) \
template <typename... Args> \
inline void topic##_##level(Args&& ... args) { \
if ( topic##_DEBUGGING && topic##_DEBUGGING_LEVEL >= DEBUG_LEVEL_##level ) \
Logger::func(std::forward<Args>(args)...); \
}
#define REGISTER_DEBUG(topic) \
REGISTER_DEBUG_FUNC(topic, LOG, log) \
REGISTER_DEBUG_FUNC(topic, ERROR, error) \
REGISTER_DEBUG_FUNC(topic, WARNING, warning) \
REGISTER_DEBUG_FUNC(topic, INFO, info) \
REGISTER_DEBUG_FUNC(topic, DEBUG, debug) \
REGISTER_DEBUG_FUNC(topic, TRACE, trace)
// wireless.h
REGISTER_DEBUG(WIRELESS)