github.com/afumu/libc@v0.0.6/musl/src/stdio/__overflow.c (about)

     1  #include "stdio_impl.h"
     2  
     3  int __overflow(FILE *f, int _c)
     4  {
     5  	unsigned char c = _c;
     6  	if (!f->wend && __towrite(f)) return EOF;
     7  	if (f->wpos != f->wend && c != f->lbf) return *f->wpos++ = c;
     8  	if (f->write(f, &c, 1)!=1) return EOF;
     9  	return c;
    10  }