Re: [Libmesh-users] errno error

[John P. <jwp...@gm...>]

On Tue, Nov 14, 2017 at 11:23 PM, Griffith, Boyce Eugene <
bo...@em...> wrote:

> We are running into a problem with errno and/or ENOMEM on an Ubuntu system
> using either Clang 3.8 or GCC 5.4, which are the compilers on whatever LTS
> version of Ubuntu is being used on this system.
>
> With clang, the error looks like:
>
> ==========
>
> make[2]: Entering directory '/srv/clang-sfw/linux/libmesh/
> 1.2.0/objs-debug'
> CXX      src/mesh/libmesh_dbg_la-exodusII_io_helper.lo
> In file included from ../LIBMESH/src/mesh/exodusII_io_helper.C:32:
> In file included from ./include/libmesh/system.h:30:
> In file included from ./include/libmesh/fem_function_base.h:29:
> In file included from ./include/libmesh/dense_vector.h:31:
> In file included from ../LIBMESH/contrib/eigen/eigen/Eigen/Dense:1:
> In file included from ../LIBMESH/contrib/eigen/eigen/Eigen/Core:256:
> ../LIBMESH/contrib/eigen/eigen/Eigen/src/Core/util/Memory.h:168:5: error:
> use of undeclared identifier
>     '__errno_location'; did you mean 'exII::__errno_location'?
>   errno = ENOMEM; // according to the standard
>   ^
> /usr/include/x86_64-linux-gnu/bits/errno.h:54:20: note: expanded from
> macro 'errno'
> #   define errno (*__errno_location ())
>                  ^
> /usr/include/x86_64-linux-gnu/bits/errno.h:50:13: note:
> 'exII::__errno_location' declared here
> extern int *__errno_location (void) __THROW __attribute__ ((__const__));
>           ^
> 1 error generated.
> Makefile:14763: recipe for target 'src/mesh/libmesh_dbg_la-exodusII_io_helper.lo'
> failed
> make[2]: *** [src/mesh/libmesh_dbg_la-exodusII_io_helper.lo] Error 1
> CXX      src/mesh/libmesh_dbg_la-nemesis_io_helper.lo
> In file included from ../LIBMESH/src/mesh/nemesis_io_helper.C:31:
> In file included from ./include/libmesh/numeric_vector.h:32:
> In file included from ./include/libmesh/dense_subvector.h:25:
> In file included from ./include/libmesh/dense_vector.h:31:
> In file included from ../LIBMESH/contrib/eigen/eigen/Eigen/Dense:1:
> In file included from ../LIBMESH/contrib/eigen/eigen/Eigen/Core:256:
> ../LIBMESH/contrib/eigen/eigen/Eigen/src/Core/util/Memory.h:168:5: error:
> use of undeclared identifier
>     '__errno_location'; did you mean 'exII::__errno_location'?
>   errno = ENOMEM; // according to the standard
>   ^
> /usr/include/x86_64-linux-gnu/bits/errno.h:54:20: note: expanded from
> macro 'errno'
> #   define errno (*__errno_location ())
>                  ^
> /usr/include/x86_64-linux-gnu/bits/errno.h:50:13: note:
> 'exII::__errno_location' declared here
> extern int *__errno_location (void) __THROW __attribute__ ((__const__));
>           ^
> 1 error generated.
> Makefile:14987: recipe for target 'src/mesh/libmesh_dbg_la-nemesis_io_helper.lo'
> failed
>
> ==========
>
> It looks like there is an attempt to work around this on some compilers
> (LIBMESH_COMPILER_HAS_BROKEN_ERRNO_T), but manually setting that flag to
> 1 did not seem to make any difference.
>
> This is with libMesh 1.2.0.
>
> Is there an easy workaround?
>

I think that --disable-eigen can also "fix" this, with the obvious caveat
that you won't be able to use eigen.

Short of that fix, using a different compiler is probably the quickest
thing to try.

My theory about this error was that it is caused when the C header file
<errno.h> is included from within a C++ namespace.

A workaround that fixed the problem on at least one system was to just
#include <errno.h> before the enclosing namespace, but that fix does not
appear to work in general...

-- 
John