Re: [ANNOUNCEMENT] TEST RELEASE: Cygwin 2.10.0-0.1

[Yaakov Selkowitz <yselkowitz at cygwin dot com>]

On 2018-01-24 13:25, Ken Brown wrote:
> On 1/20/2018 6:49 PM, Ken Brown wrote:
>> On 1/20/2018 7:23 AM, Ken Brown wrote:
>>> On 1/19/2018 10:27 PM, Ken Brown wrote:
>>>> Here's another issue that's come up with _FORTIFY_SOURCE.  One of the 
>>>> emacs source files, fileio.c, makes use of a pointer to readlinkat. 
>>>> When _FORTIFY_SOURCE > 0, this leads to an "undefined reference to 
>>>> `__ssp_protected_readlinkat'" linking error.  Does this sound like 
>>>> something that will be fixed with the new gcc release?
>>>
>>> I got to this sooner than expected:
>>>
>>> $ cat ssp_test.c
>>> #define  _FORTIFY_SOURCE 1
>>> #include <unistd.h>
>>> void foo (ssize_t (*preadlinkat) (int, char const *, char *, size_t));
>>>
>>> void baz ()
>>> {
>>>    foo (readlinkat);
>>> }
> 
> The following patch seems to fix the problem:
> 
> -#define __ssp_inline extern __inline__ __attribute__((__always_inline__, __gnu_inline__))
> +#define __ssp_inline extern __inline__ __attribute__((__always_inline__))

No, that would have other consequences:

https://gcc.gnu.org/onlinedocs/gcc/Inline.html

> I arrived at this by comparing Cygwin's ssp.h with NetBSD's, on which
> Cygwin's was based, and I noticed that NetBSD didn't use __gnu_inline__.

The BSDs also stuck with GCC 4.2 due to licensing reasons, so you can't
always compare.

> Yaakov, is there a reason that Cygwin needs __gnu_inline__?

Because the semantics of inline changed in GCC 4.3.

> It apparently prevents fortified functions from being used as function pointers.

I am currently testing the following, which seems to match glibc in this
detail:

--- a/newlib/libc/include/ssp/ssp.h
+++ b/newlib/libc/include/ssp/ssp.h
@@ -51,7 +51,6 @@
                __chk_fail()
 #define __ssp_decl(rtype, fun, args) \
 rtype __ssp_real_(fun) args __asm__(__ASMNAME(#fun)); \
-__ssp_inline rtype fun args __asm__(__ASMNAME("__ssp_protected_" #fun)); \
 __ssp_inline rtype fun args
 #define __ssp_redirect_raw(rtype, fun, args, call, cond, bos) \
 __ssp_decl(rtype, fun, args) \

-- 
Yaakov

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