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Date: Sat, 11 Jul 2020 16:39:22 +0200
From: tlaronde@polynum.com
To: ori@eigenstate.org
Cc: 9front@9front.org
Subject: Re: [FOUND] [9front] putc/fputc incorrect return
Message-ID: <20200711143922.GB563@polynum.com>
References: <20200709182924.GA465@polynum.com>
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Here is the simple code exhibiting the problem. There are three
components:

1) int is negative;
2) there are at least two successive calls;
3) the stream is neither stdout nor stderr.

#include <u.h>
#include <stdio.h>

int
main(int argc, char *argv[])
{
	FILE *fp;
	short w;

	if ( (fp = fopen("/tmp/bug.tfm", "wb")) == NULL ) {
		(void)fprintf(stderr, "Unable to open '/tmp/bug.tfm' for writing.\n");
		return 1;
	}

	/* Writing successively negative word on the file stream: bug.
	 */
	w = 0xffaa;
	(void)fprintf(stderr, "\nWriting big endian '%#hx' on file stream returned"
		" -> %#x %#x\n", w, putc(w >> 8, fp), putc(w, fp));

	/* On stdout, no problem.
	 */
	(void)fprintf(stderr, "\nWriting big endian '%#hx' on stdout returned"
		" -> %#x %#x\n", w, putc(w >> 8, stdout), putc(w, stdout));

	return 0;
}

Best,
-- 
        Thierry Laronde <tlaronde +AT+ polynum +dot+ com>
                     http://www.kergis.com/
                       http://www.sbfa.fr/
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