Hi
I am playing with the printf and the idea to write a my_printf(...) that calls the normal printf and a sprintf that sends the result to a special function. (I was thinking about sprintf since that behaves just like printf on most platforms).
My idea was to write a small macro that did this:
#define my_printf(X, Y...) do{ printf(X, ## Y); \ char* data = malloc(strlen(X)*sizeof(char)); \ sprintf(data, X, ## Y); \ other_print(data);\ free(data);}while(0)
But since sprintf can expand the string to a much bigger size than X, this method breaks almost directly.
And just to add a number do the malloc seems to be the wrong way to attack the problem, since then I would just move the problem into the future and a day when I want print a big expression...
Does anyone has a better idea on how to attack this problem? Or how do I know how big the sprintf result will be?
Thanks Johan
Update: I forgot that printf returns how many chars it prints, and since I already is calling printf in the macro it was a very easy thing to add a int that saves the number.
#define buf_printf(X, Y...) do{ int len = printf(X, ## Y); \ char* data = malloc((len+1)*sizeof(char)); \ sprintf(data, X, ## Y); \ other_print(data);\ free(data);}while(0)
Update: I was thinking about this and maybe to use a normal function that looks a lot like what ephemient has suggested is a good idea. The key there seems to be the v-version of the different printf functions (vprintf, vsprintf and vsnprintf). Thanks for pointing that out.
Thanks again Johan