Support dynamic object loading on MS-Windows.

w32/include/dlfcn.h: New file.
 w32/compat/posixfcn.c: Include dlfcn.h.
 (dlopen, dlerror, dlsym) [MAKE_LOAD]: New functions, in support of
 dynamic loading.

 config.h.W32.template (MAKE_LOAD): Define.
 load.c (load_object) [HAVE_DOS_PATHS]: Support backslashes and
 drive letters in file names of dynamic objects.

ChangeLog

@@ -1,5 +1,16 @@
 2013-04-29  Eli Zaretskii  <eliz@gnu.org>
 
+	* w32/include/dlfcn.h: New file.
+
+	* w32/compat/posixfcn.c: Include dlfcn.h.
+	(dlopen, dlerror, dlsym) [MAKE_LOAD]: New functions, in support of
+	dynamic loading.
+
+	* config.h.W32.template (MAKE_LOAD): Define.
+
+	* load.c (load_object) [HAVE_DOS_PATHS]: Support backslashes and
+	drive letters in file names of dynamic objects.
+
 	* job.c (construct_command_argv_internal) [WINDOWS32]: Return
 	right after generating new_argv for one_shell case.  This fixes
 	the Windows build for both Unixy shell and stock Windows shells.

config.h.W32.template

@@ -366,6 +366,9 @@ this program.  If not, see <http://www.gnu.org/licenses/>.  */
 /* Define to 1 to enable job server support in GNU make. */
 #define MAKE_JOBSERVER 1
 
+/* Define to 1 to enable 'load' support in GNU make. */
+#define MAKE_LOAD 1
+
 /* Define to 1 to enable symbolic link timestamp checking. */
 /* #undef MAKE_SYMLINKS */
 

load.c

@@ -49,7 +49,11 @@ load_object (const gmk_floc *flocp, int noerror,
     void *dlp = NULL;
 
     /* If the path has no "/", try the current directory first.  */
-    if (! strchr (ldname, '/'))
+    if (! strchr (ldname, '/')
+#ifdef HAVE_DOS_PATHS
+	&& ! strchr (ldname, '\\')
+#endif
+	)
       dlp = dlopen (concat (2, "./", ldname), RTLD_LAZY|RTLD_GLOBAL);
 
     /* If we haven't opened it yet, try the default search path.  */
@@ -134,6 +138,20 @@ load_file (const gmk_floc *flocp, const char **ldname, int noerror)
       char *p = new;
 
       fp = strrchr (*ldname, '/');
+#ifdef HAVE_DOS_PATHS
+      if (fp)
+	{
+	  const char *fp2 = strchr (fp, '\\');
+
+	  if (fp2 > fp)
+	    fp = fp2;
+	}
+      else
+	fp = strrchr (*ldname, '\\');
+      /* The (improbable) case of d:foo.  */
+      if (fp && *fp && fp[1] == ':')
+	fp++;
+#endif
       if (!fp)
         fp = *ldname;
       else

w32/compat/posixfcn.c

@@ -21,6 +21,8 @@ this program.  If not, see <http://www.gnu.org/licenses/>.  */
 #include <errno.h>
 #include <windows.h>
 
+#include "dlfcn.h"
+
 #include "makeint.h"
 #include "job.h"
 
@@ -256,3 +258,86 @@ same_stream (FILE *f1, FILE *f2)
 }
 
 #endif	/* OUTPUT_SYNC */
+
+#if MAKE_LOAD
+
+/* Support for dynamic loading of objects.  */
+
+
+static DWORD last_err;
+
+void *
+dlopen (const char *file, int mode)
+{
+  char dllfn[MAX_PATH], *p;
+  HANDLE dllhandle;
+
+  if ((mode & ~(RTLD_LAZY | RTLD_NOW | RTLD_GLOBAL)) != 0)
+    {
+      errno = EINVAL;
+      last_err = ERROR_INVALID_PARAMETER;
+      return NULL;
+    }
+
+  if (!file)
+    dllhandle = GetModuleHandle (NULL);
+  else
+    {
+      /* MSDN says to be sure to use backslashes in the DLL file name.  */
+      strcpy (dllfn, file);
+      for (p = dllfn; *p; p++)
+	if (*p == '/')
+	  *p = '\\';
+
+      dllhandle = LoadLibrary (dllfn);
+    }
+  if (!dllhandle)
+    last_err = GetLastError ();
+
+  return dllhandle;
+}
+
+char *
+dlerror (void)
+{
+  static char errbuf[1024];
+  DWORD ret;
+
+  if (!last_err)
+    return NULL;
+
+  ret = FormatMessage (FORMAT_MESSAGE_FROM_SYSTEM
+		       | FORMAT_MESSAGE_IGNORE_INSERTS,
+		       NULL, last_err, 0, errbuf, sizeof (errbuf), NULL);
+  while (ret > 0 && (errbuf[ret - 1] == '\n' || errbuf[ret - 1] == '\r'))
+    --ret;
+
+  errbuf[ret] = '\0';
+  if (!ret)
+    sprintf (errbuf, "Error code %lu", last_err);
+
+  last_err = 0;
+  return errbuf;
+}
+
+void *
+dlsym (void *handle, const char *name)
+{
+  FARPROC addr = NULL;
+
+  if (!handle || handle == INVALID_HANDLE_VALUE)
+    {
+      last_err = ERROR_INVALID_PARAMETER;
+      return NULL;
+    }
+
+  addr = GetProcAddress (handle, name);
+  if (!addr)
+    last_err = GetLastError ();
+
+  return (void *)addr;
+}
+
+
+#endif	/* MAKE_LOAD */
+

w32/include/dlfcn.h

@@ -0,0 +1,13 @@
+/* dlfcn.h replacement for MS-Windows build.  */
+#ifndef DLFCN_H
+#define DLFCN_H
+
+#define RTLD_LAZY   1
+#define RTLD_NOW    2
+#define RTLD_GLOBAL 4
+
+extern void *dlopen (const char *, int);
+extern void *dlsym (void *, const char *);
+extern char *dlerror (void);
+
+#endif	/* DLFCN_H */