Eclipse - make the fflush(stdout) as default after

Question

Having same case.

Is there any solution such that the fflush(stdout) will occur automatically after printf() instead of add fflush(stdout) after each printf() calling ?

I using Eclipse IDE for C/C++ Developers and gcc --version gcc (GCC) 4.8.1 on windows 7

Answer 1

If you want to disable buffering globally, you can use setvbuf:

setvbuf(stdout, NULL, _IONBF, 0);

at the beginning of your program.

If you want to do it only for some calls, you can define your own macro to do so, like:

#define printflush(s, ...) do { printf(s, __VA_ARGS__); fflush(stdout); } while (0)

which puts the two function calls inside a new scope with a trick.

In both cases, you will need to have at least two arguments (like printflush("id = %d\n", id)), or you will cause a syntax error at compile time.

GCC specific solution to the problem above: you can extend the macro above so that it works with a single parameter too:

#define printflush(s, ...) do { printf(s, ##__VA_ARGS__); fflush(stdout); } while (0)

This way, you can use it also with printflush("Hey!").

EDIT: as pointed out by @unwind, variadic macros have been standardized in C99. Still, GCC 4.8 will understand them without any extra switch.