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




On 1/24/2018 7:16 PM, Yaakov Selkowitz wrote:
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) \

Works for me.

Ken


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