[libvirt] [PATCH] driver: conditionalize use of dlopen functions & use mingw-dlfcn

[Peter Krempa]

On Wed, Aug 02, 2017 at 11:26:06 +0100, Daniel Berrange wrote:
> Not every platform is guaranteed to have dlopen/dlsym, so we should
> conditionalize its use. Suprisingly it is actually present for Win32
> via the mingw-dlfcn add on, but we should still conditionalize it.
> 
> Signed-off-by: Daniel P. Berrange <berrange at redhat.com>
> ---
>  configure.ac          |  2 +-
>  mingw-libvirt.spec.in |  2 ++
>  src/driver.c          | 18 ++++++++++++++++--
>  3 files changed, 19 insertions(+), 3 deletions(-)
> 
> diff --git a/configure.ac b/configure.ac
> index b12b7fae1..2b3375138 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -328,7 +328,7 @@ dnl Availability of various common headers (non-fatal if missing).
>  AC_CHECK_HEADERS([pwd.h regex.h sys/un.h \
>    sys/poll.h syslog.h mntent.h net/ethernet.h linux/magic.h \
>    sys/un.h sys/syscall.h sys/sysctl.h netinet/tcp.h ifaddrs.h \
> -  libtasn1.h sys/ucred.h sys/mount.h stdarg.h])
> +  libtasn1.h sys/ucred.h sys/mount.h stdarg.h dlfcn.h])

A similar check is done in m4/virt-dlopen.m4:

AC_CHECK_HEADER([dlfcn.h],, [with_dlfcn=no])

Is it not enough? We already use HAVE_DLFCN_H in few places.

>  dnl Check whether endian provides handy macros.
>  AC_CHECK_DECLS([htole64], [], [], [[#include <endian.h>]])
>  AC_CHECK_FUNCS([stat stat64 __xstat __xstat64 lstat lstat64 __lxstat __lxstat64])
> diff --git a/mingw-libvirt.spec.in b/mingw-libvirt.spec.in
> index 553d14022..dcb0837f7 100644
> --- a/mingw-libvirt.spec.in
> +++ b/mingw-libvirt.spec.in
> @@ -54,6 +54,8 @@ BuildRequires:  mingw32-libxml2
>  BuildRequires:  mingw64-libxml2
>  BuildRequires:  mingw32-portablexdr
>  BuildRequires:  mingw64-portablexdr
> +BuildRequires:  mingw32-dlfcn
> +BuildRequires:  mingw64-dlfcn
>  
>  BuildRequires:  pkgconfig
>  # Need native version for msgfmt
> diff --git a/src/driver.c b/src/driver.c
> index 2e7dd01df..04dd0a443 100644
> --- a/src/driver.c
> +++ b/src/driver.c
> @@ -34,10 +34,11 @@ VIR_LOG_INIT("driver");
>  
>  
>  /* XXX re-implement this for other OS, or use libtools helper lib ? */
> -
> -#include <dlfcn.h>
>  #define DEFAULT_DRIVER_DIR LIBDIR "/libvirt/connection-driver"
>  
> +#ifdef HAVE_DLFCN_H
> +# include <dlfcn.h>
> +
>  
>  static void *
>  virDriverLoadModuleFile(const char *file)
> @@ -126,6 +127,19 @@ virDriverLoadModuleFull(const char *path,
>      return ret;
>  }
>  
> +#else /* ! HAVE_DLFCN_H */
> +int
> +virDriverLoadModuleFull(const char *path ATTRIBUTE_UNUSED,
> +                        const char *regfunc ATTRIBUTE_UNUSED,
> +                        void **handle)
> +{
> +    VIR_DEBUG("dlopen not available on this platform");
> +    if (handle)
> +        *handle = NULL;
> +    return -1;
> +}
> +#endif /* ! HAVE_DLFCN_H */

ACK
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