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One can remove all calls to printf() using #define printf. What if I have a lot of debug prints like std::cout << x << endl; ? How can I quickly switch off cout << statements in a single file using preprocessor?
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The #define creates a macro, which is the association of an identifier or parameterized identifier with a token string. After the macro is defined, the compiler can substitute the token string for each occurrence of the identifier in the source file.
Use const Instead of #define to Define Constants.
__VA_OPT__ is a new feature of variadic macros in C++20. It lets you optionally insert tokens depending on if a variadic macro is invoked with additional arguments. An example usage is comma elision in a standardized manner.
The preprocessor performs preliminary operations on C and C++ files before they are passed to the compiler. You can use the preprocessor to conditionally compile code, insert files, specify compile-time error messages, and apply machine-specific rules to sections of code.
As "unwind" already said, the quick solution is a do-nothing stream. There are better implementations though:
class NullStream {
public:
NullStream() { }
template<typename T> NullStream& operator<<(T const&) { return *this; }
};
You still have a slight issue with std::cout since that's a sequence of three tokens, and you really don't want to redefine std or cout individually. A simple solution is
#ifdef NDEBUG
#define COUT std::cout
#else
#define COUT NullStream()
#endif
COUT << "Hello, world" << std::endl;
As a general principle logging to stdout should be avoided - far better to log to a logfile, and then you can use standard configuration tools to change log levels, or turn it off altogether.
Just my $0.02.....
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