Fix interfacing with and remaking dynamic objects on MS-Windows.

 load.c (load_object, load_file): Accept an additional argument
 DLP and return in it a pointer that can be used to unload the
 dynamic object.
 read.c (eval): Call load_file with an additional argument, and
 record the pointer returned there in the 'struct file' object of
 dynamic objects in that object's 'struct file'.
 commands.c (execute_file_commands): Unload dynamic objects
 before remaking them, to avoid failure to remake if the OS doesn't
 allow overwriting objects that are in use.
 filedef.h (struct file): New member dlopen_ptr.
 gnumake.h (GMK_EXPORT): Define to dllexport/dllimport
 decorations for Windows and to nothing on other platforms.
 (gmk_eval, gmk_expand, gmk_add_function): Add GMK_EXPORT qualifier
 to prototypes.
 makeint.h (MAIN): Define before including gnumake.h, to give
 correct dllexport decorations to exported functions.
 (load_file): Adjust prototype.
 loadapi.c: Don't include gnumake.h, since makeint.h already
 includes it, and takes care of defining MAIN before doing so.
 build_w32.bat (LinkGCC): Produce an import library for functions
 exported by Make for loadable dynamic objects.

 w32/compat/posixfcn.c (dlclose): New function.
 w32/include/dlfcn.h (dlclose): Add prototype.

 scripts/features/load: Fix signatures of testload_gmk_setup and
 explicit_setup, to bring them in line with the documentation.

1 files changed, 8 insertions, 0 deletions

diff --git a/commands.c b/commands.c
index 698816f..e8a9f1c 100644
--- a/commands.c
+++ b/commands.c
@@ -14,6 +14,8 @@ A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
 You should have received a copy of the GNU General Public License along with
 this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
+#include <dlfcn.h>
+
 #include "makeint.h"
 #include "dep.h"
 #include "filedef.h"
@@ -468,6 +470,12 @@ execute_file_commands (struct file *file)
 
   set_file_variables (file);
 
+  /* If this is a loaded dynamic object, unload it before remaking.
+     Some systems don't allow to overwrite a loaded shared
+     library.  */
+  if (file->dlopen_ptr)
+    dlclose (file->dlopen_ptr);
+
   /* Start the commands running.  */
   new_job (file);
 }