Ping 3: [PATCH] more out of bounds checking improvements

[Martin Sebor <msebor@gmail.com>]

Ping: still looking for an approval of the patch below before
tomorrow's freeze:
https://sourceware.org/pipermail/libc-alpha/2020-December/120586.html

On 1/4/21 8:54 AM, Martin Sebor wrote:
> Joseph or anyone else: is the patch below okay to commit?  I'd like
> to include it in the upcoming release.
> 
> https://sourceware.org/pipermail/libc-alpha/2020-December/120586.html
> 
> On 12/18/20 9:56 AM, Martin Sebor wrote:
>> Ping: Does the last patch look good enough to commit?
>> https://sourceware.org/pipermail/libc-alpha/2020-December/120586.html
>>
>> On 12/9/20 2:46 PM, Martin Sebor wrote:
>>> On 10/26/20 10:08 AM, Joseph Myers wrote:
>>>> 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).
>>>
>>> I don't know enough about the Glibc build infrastructure to
>>> understand your suggestion but either approach sounds more involved
>>> than I have cycles for so I propose the scaled patch instead, without
>>> the ctermid and cuserid changes (and without the nonnull attribute
>>> on readv/writev(*)).  Hopefully someone with more experience with
>>> the existing scheme will find a way to define the two macros and
>>> make use of them to enable the detection for these two functions
>>> as well.
>>>
>>> Martin
>>>
>>> [*] I'll submit that patch separately.
>>
>