musl/src/stdio/fwide.c

#include "stdio_impl.h"

#define SH (8*sizeof(int)-1)
#define NORMALIZE(x) ((x)>>SH | -((-(x))>>SH))

int fwide(FILE *f, int mode)
{
	FLOCK(f);
	if (!f->mode) mode = f->mode = NORMALIZE(mode);
	FUNLOCK(f);
	return mode;
}