svn commit: r303988 - head/lib/libc/gen

[Bryan Drewery]

On 8/24/16 1:30 PM, Bryan Drewery wrote:
> On 8/24/16 1:26 PM, Eric van Gyzen wrote:
>> On 08/24/2016 15:16, Bryan Drewery wrote:
>>> On 8/24/16 1:12 PM, Eric van Gyzen wrote:
>>>> On 08/24/2016 15:01, Ed Schouten wrote:
>>>>> 2016-08-24 21:53 GMT+02:00 Bryan Drewery <bdrewery at freebsd.org>:
>>>>>> Is it possible to cause the use of these old prototypes to print a
>>>>>> warning and note that they are deprecated/unsafe?
>>>>>
>>>>> That's a good question. In theory, we could annotate these functions
>>>>> with __attribute__((__deprecated__)):
>>>>>
>>>>> https://gcc.gnu.org/onlinedocs/gcc-3.3.4/gcc/Type-Attributes.html
>>>>>
>>>>> But I'm actually too afraid to use it. In the worst case it may cause
>>>>> the compiler to generate a warning even when basename()/dirname() is
>>>>> used correctly, as __old_* will still be part of the compiled
>>>>> expression.
>>>>
>>>> Could __warn_references() be used, as libc currently does for gets() and
>>>> others?
>>>>
>>>> Eric
>>>>
>>>
>>> /usr/include/stdio.h:extern char *gets (char *__s) __wur
>>> __attribute_deprecated__;
>>> /usr/include/x86_64-linux-gnu/sys/cdefs.h:# define
>>> __attribute_deprecated__ __attribute__ ((__deprecated__))
>>>
>>> __wur being warning about unused result.
>>
>> /usr/src/lib/libc/stdio/gets.c:__warn_references(gets, "warning: this
>> program uses gets(), which is unsafe.");
> 
> Ah! Ours! I misunderstood and thought about the FORTIFY_SOURCE glibc stuff.
> 
> This is a linker warning.  It would not be as obvious which line is the
> problem but would still tell the user they have potentially unsafe code.
>  They also may not care if not using threads.

Ah no it is specific, great:

> xinstall.o: In function `makelink':
> /root/svn/releng/11.0/usr.bin/xinstall/xinstall.c:688: warning: warning: this program uses basename(const char *), which is deprecated and thread-unsafe.

Not sure what I think about it though.

> 
> We would need to move old_dirname/basename into their own .c files to
> use this I think. Playing around with that...
> 
>>
>>> As for actually using it here, I tried adding it onto the
>>> _old_dirname/basename prototypes.  It produces an error, fine, in the
>>> bootstrap build for xinstall it would not error, great.  However, for
>>> building xinstall on head where it will not use the __old_dirname and
>>> will use the new dirname at FBSD_1.5, it _still_ complains about using the
>>> __old_dirname() prototype via __generic and errors in the wrong case.
> 
> 


-- 
Regards,
Bryan Drewery

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