Re: [PATCH] more out of bounds checking improvements

[Joseph Myers <joseph@codesourcery.com>]

On Mon, 26 Oct 2020, Martin Sebor via Libc-alpha wrote:

> The patch introduces the _L_tmpnam macro to avoid polluting
> the POSIX <unistd.h> namespace with L_tmpnam when the latter is
> only supposed to be defined in <stdio.h>.  This in turn causes
> the a number of POSIX conformance test failures that I haven't
> been able to figure how to deal with and need some help with.
> 
> In file included from ../include/unistd.h:2,
>                  from /tmp/tmpzm39v4n3/test.c:1:
> ../posix/unistd.h:1159:32: error: ‘_L_ctermid’ undeclared here (not in a
> function)
>  extern char *ctermid (char __s[_L_ctermid]) __THROW
>                                 ^~~~~~~~~~
> 
> I expected adding the new macros to stdio-common/stdio_lim.h.in
> would do the trick but clearly something else is needed and I'm
> at a lost as to what that might be.  I haven't been able to find

<unistd.h> doesn't include <bits/stdio_lim.h>, and you're making 
<unistd.h> use _L_ctermid, and you're only defining _L_ctermid in 
<bits/stdio_lim.h>.  You need to define it in a header that <unistd.h> 
includes - which also needs to be one whose contents are namespace-clean 
for inclusion in <unistd.h> (which <bits/stdio_lim.h> isn't).

The obvious way would be to have a new installed (i.e. add to "headers" in 
the relevant Makefile) header for the new macros that can be included in 
both <stdio.h> and <unistd.h>.  Suggestion: the existing scheme for 
automatic generation of bits/stdio_lim.h is overly complicated, it would 
be better to use sysdeps headers in the normal way like for other bits/ 
headers where the values may depend on the glibc configuration (and then 
to have testcases that verify consistently of OPEN_MAX and FOPEN_MAX / of 
PATH_MAX and FILENAME_MAX, when both are defined).

-- 
Joseph S. Myers
joseph@codesourcery.com