Forwarding from the gnulib list; is this something we should fix in cygwin proper?
On 01/31/2018 04:42 AM, Bruno Haible wrote:
> On 64-bit Cygwin, a libunistring build fails like this:
>
> $ /bin/sh ../libtool --tag=CC --preserve-dup-deps --mode=link
> x86_64-pc-cygwin-gcc -g -O2 -L/usr/local/cygwin64/lib
> -Wl,--disable-auto-import -o test-environ.exe test-environ.o libtests.a
> ../lib/libunistring.la libtests.a
> libtool: link: x86_64-pc-cygwin-gcc -g -O2 -Wl,--disable-auto-import -o
> .libs/test-environ.exe test-environ.o -L/usr/local/cygwin64/lib libtests.a
> ../lib/.libs/libunistring.dll.a -liconv libtests.a -L/usr/local/cygwin64/lib
> test-environ.o:test-environ.c:(.rdata$.refptr.environ[.refptr.environ]+0x0):
> undefined reference to `environ'
> collect2: error: ld returned 1 exit status
>
> This fixes it.
>
>
> 2018-01-31 Bruno Haible <br...@clisp.org>
>
> environ: Fix link error on 64-bit Cygwin.
> * lib/unistd.in.h (environ): On Cygwin, redeclare with the
> __declspec(dllimport) attribute.
> * doc/posix-functions/environ.texi: Mention the Cygwin problem.
>
> diff --git a/doc/posix-functions/environ.texi
> b/doc/posix-functions/environ.texi
> index 34ac25a..a6c0095 100644
> --- a/doc/posix-functions/environ.texi
> +++ b/doc/posix-functions/environ.texi
> @@ -24,6 +24,9 @@ shared libraries on Mac OS X 10.5. Here is a workaround:
> Instead, one can use
> #define environ (*_NSGetEnviron())
> @end smallexample
> This works at all versions of Mac OS X.
> +@item
> +On Cygwin in 64-bit mode, references to this variable cause a link error when
> +the option @code{-Wl,--disable-auto-import} is in use.
> @end itemize
>
> Portability problems not fixed by Gnulib:
> diff --git a/lib/unistd.in.h b/lib/unistd.in.h
> index 6802e3b..4ef0ffa 100644
> --- a/lib/unistd.in.h
> +++ b/lib/unistd.in.h
> @@ -400,6 +400,13 @@ _GL_WARN_ON_USE (dup3, "dup3 is unportable - "
>
>
> #if @GNULIB_ENVIRON@
> +# if defined __CYGWIN__
> +/* The 'environ' variable is defined in a DLL. Therefore its declaration
> needs
> + the '__declspec(dllimport)' attribute, but the system's <unistd.h> lacks
> it.
> + This leads to a link error on 64-bit Cygwin when the option
> + -Wl,--disable-auto-import is in use. */
> +_GL_EXTERN_C __declspec(dllimport) char **environ;
> +# endif
> # if !@HAVE_DECL_ENVIRON@
> /* Set of environment variables and values. An array of strings of the form
> "VARIABLE=VALUE", terminated with a NULL. */
>
>
>
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
signature.asc
Description: OpenPGP digital signature
