On Tue, 12 Jun 2012, Bin.Cheng wrote: > >> I noticed that GCC now can check format string of printf functions, so > >> I am wondering if it is possible to take advantage of this utility, by > >> making gcc detect whether printf prints floating point number and then > >> generate assembly directive in backend to pull in floating point > >> functions only if necessary. > > > > Obviously this won't help if the program is using functions such as > > vprintf to print things with variable format strings.... > One method is to analyze the type of arguments when format strings are > varying. Though this method might fail when user trying to output a > "long long" type int with conversion specifier "%f", I think it's not > a big deal.
That method won't help for vprintf (unless you do something more complicated and interprocedural) since then you have just a (probably nonconstant) format strict and a (definitely nonconstant) va_list so don't know the types of the arguments at all. -- Joseph S. Myers jos...@codesourcery.com
