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Re: [RFC]New implementation of C89 streamio for resource limited bare metal systems

W dniu 2013-06-07 11:05, Bin Cheng pisze:
2) This implementation substantially decreases stack usage for printf
routines, because of a char[1024] buffer in newlib's __sbprintf function.
This can be fixed by simply disabling the optimization for un-buffered files
(under configuration options).

So we can even drop this implementation and achieving same code size goal.

An option like that (maybe even an configure option for setting BUFSIZ without messing with source files [; ) would be great! Unbuffered stream should be unbuffered [;

But one challenge is how to make floating point weak symbol without
re-implement the stream io routines, because floating point is tight coupled
with integer in current implementation.

Well, if you don't want to use floating point AT ALL you can just redefine all *printf to be *iprintf (and the same for scanf). I guess it would be enough to have sth like this added to compilation:

-Dprintf=iprintf -Dfprintf=fiprintf -Dsprintf=siprintf ... -Dscanf=iscanf -Dfscanf=fiscanf -Dsscanf=siscanf ... (for all available "types" of these functions)

The only case where this would NOT work is if newlib itself uses floating point variants of these functions "inside". Does it? In that case maybe it would be possible to override the symbols via linker script or by just providing trampoline function(s) (vfprintf() calling vfiprintf() would probably be enough).


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