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Date: Wed, 17 Aug 2022 18:38:52 -0400
From: Rich Felker <dalias@...c.org>
To: musl@...ts.openwall.com
Subject: Re: Broken freopen() does not reset fwide()
On Wed, Aug 17, 2022 at 11:11:31AM -0400, Rich Felker wrote:
> On Tue, Aug 16, 2022 at 06:33:35PM +0000, Anonymousemail wrote:
> > Powered by Anonymousemail → [1]Join Us!
> >
> > I'm using musl based distribution.
> > The official example from https://en.cppreference.com/w/c/io/fwide is
> > malfunctioning, musl does not reset the fwide(), returns -1 (meaning BYTE
> > oriented).
> >
> > Output from example on musl:
> > 1) A newly opened stream has no orientation.
> > no orientation
> > 2) Establish byte orientation.
> > narrow orientation
> > narrow character read '#'
> > wide character read 'i'
> > 3) Only freopen() can reset stream orientation.
> > 4) A reopened stream has no orientation.
> > narrow orientation <- problem detected here, should say "no
> > orientation"
> > 5) Establish wide orientation.
> > narrow orientation
> > narrow character read '#'
> > wide character read 'i'
> >
> > Another simple example to reproduce the issue.:
> > #include <stdio.h>
> > #include <wchar.h>
> > #include <stdlib.h> // for EXIT_SUCCESS
> > #include <assert.h>
> >
> > int main() {
> > enum { narrow = -1, query = 0, wide = 1 };
> > FILE* test = fopen("test.bin", "r");
> > if(!test) {
> > puts("You need to have test.bin file.");
> > abort();
> > }
> > // establish NARROW orientation
> > fwide(test, narrow);
> > // reopen to reset, broken on musl
> > freopen("test.bin", "r", test);
> > assert(fwide(test, query) == 0); // will fail on musl
> > // CLEANUP
> > fclose(test);
> > // Exit the program
> > return EXIT_SUCCESS;
> > }
> >
> > -----
> > Save as main.c, run with
> > cc main.c
> > echo test >test.bin
> > ../a.out
> >
> > Will output
> > Assertion failed: fwide(test, query) == 0 (main2.c: main: 17)
> > Aborted
>
> Indeed this looks like an oversight. I'll need to look at what it will
> take to fix it. Naively, just f->wide = 0 before successful return in
> freopen seems ok, but probably also f->locale needs to be set to 0 to
> reset the encoding rule, and it might be necessary to null out some
> buffer pointers to force future calls to stdio functions to reprobe
> the width.
>
> Thanks for the report.
>
> BTW is there a way you can fix the mailer you're using? The plain text
> version of your mail was not plain text, but was littered with html
> entities ( etc.) making it unreadable, so I rendered the html
> version to text in order to be able to reply.
OK, fflush took care of the buffer pointers already, so just setting
f->mode and f->locale to 0 should be fine. I'll commit a fix.
Rich
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