modules: huge simplification of module loading without libltdl.

Libltdl is huge and slow, and carrying the weight of support for
decades old systems.  We can do much better using POSIX dlopen
and dlsym directly, simplifying and speeding up as we do so.
* configure.ac (LT_CONFIG_LTDL_DIR, LTDL_INIT): Remove.
(M4_DEFAULT_PRELOAD): Set to ""; we lost preload support along
with removing libltdl.
* Makefile.am: Don't include ltdl/Makefile.inc.
(AM_CPPFLAGS): Manually add current directory to include search
paths.
* m4/m4private.h (includes): Remove ltdl.h.
(INIT_SYMBOL, m4__module_init): Remove.
(struct m4_module): Change handle type from lt_dlhandle to void *.
* m4/m4module.h (M4INIT_HANDLER): Remove.
* m4/module.c (includes): Add dlfcn.h.
(m4__module_interface, iface_id, m4__module_init, module_dlerror):
Remove.
(m4__module_open): Drastically simplified without all the
libltdl setup and interface id twiddling. Just call dlopen to
get a native handle, and the dlsym to get the init function.
(m4_module_import): Similarly wrt dlsym.
* m4/path.c (FILE_SUFFIXES): Replace .la and LT_MODULE_EXT with
hardcoded ".so".
(m4_load_filename): Likewise.
* modules/gnu.c: Remove libltdl preprocessor symbol renaming,
and use "include_<modulename>" as the single entry point function.
* modules/import.c, modules/m4.c, modules/modtest.c,
modules/mpeval.c, modules/shadow.c, modules/stdlib.c,
modules/time.c, modules/traditional.c: Likewise.
* main.c (main): Remove calls to m4__module_init and
LTDL_SET_PRELOADED_SYMBOLS.
* tests/m4.in: Make sure we always have the modules/.libs and
tests/.libs directories at the front of M4PATH so that the
tests will find the modules they need to include.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>

17 files changed, 70 insertions, 225 deletions

diff --git a/Makefile.am b/Makefile.am
index e9807a0f..cd1d234f 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -39,7 +39,7 @@ changelog_old		= $(srcdir)/ChangeLog.old
 # which effectively disables the auto-exporting of all other symbols.
 # Revisit this if libtool on cygwin improves.
 # See http://lists.gnu.org/archive/html/libtool-patches/2007-02/msg00062.html
-AM_CPPFLAGS	=
+AM_CPPFLAGS	= -I$(srcdir) -I.
 AM_CFLAGS	= $(WARN_CFLAGS) $(WERROR_CFLAGS)
 AM_LDFLAGS	= -export-dynamic -export-symbols-regex ".*"
 EXTRA_DIST	=
@@ -53,9 +53,6 @@ noinst_LTLIBRARIES=
 lib_LTLIBRARIES	=
 EXTRA_LTLIBRARIES=
 
-# Include Libtool's rules.
-include ltdl/Makefile.inc
-
 # Additional configuration.  Version management comes from suggestions
 # given in build-aux/git-version-gen.
 AM_CPPFLAGS    += -Ignu -I$(srcdir)/gnu \
diff --git a/configure.ac b/configure.ac
index 904f6247..6e6d722a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -47,7 +47,7 @@ dnl the m4_ namespace provided by m4sugar, so we prefer M4_ as our
 dnl package-specific prefix.
 m4_pattern_forbid([^M4_[A-Z]])
 
-AC_DEFUN([M4_DEFAULT_PRELOAD], [m4 traditional gnu])
+AC_DEFUN([M4_DEFAULT_PRELOAD], [])
 M4_default_preload="M4_DEFAULT_PRELOAD"
 
 
@@ -82,22 +82,7 @@ M4_CHECK_DEBUGGING
 ## Libtool initialization. ##
 ## ----------------------- ##
 LT_PREREQ([2.2])
-LT_CONFIG_LTDL_DIR([ltdl])
 LT_INIT([shared dlopen win32-dll])
-LTDL_INIT([nonrecursive])
-
-# The lt_dlhandle_iterate symbol was added with libtool-2.2
-if test "x$with_included_ltdl" != "xyes"; then
-  save_CFLAGS="$CFLAGS"
-  save_LDFLAGS="$LDFLAGS"
-  CFLAGS="$CFLAGS $LTDLINCL"
-  LDFLAGS="$LDFLAGS $LIBLTDL"
-  AC_CHECK_LIB([ltdl], [lt_dlhandle_iterate],
-             [],
-     [AC_MSG_ERROR([installed libltdl is too old])])
-  LDFLAGS="$save_LDFLAGS"
-  CFLAGS="$save_CFLAGS"
-fi
 
 AC_ARG_ENABLE([gcc-warnings],
   [AS_HELP_STRING([--enable-gcc-warnings],
diff --git a/m4/m4module.h b/m4/m4module.h
index 038a428b..694e77cf 100644
--- a/m4/m4module.h
+++ b/m4/m4module.h
@@ -111,17 +111,6 @@ struct m4_string_pair
   static void CONC (builtin_, name)                                     \
     (m4 *context, m4_obstack *obs, size_t argc, m4_macro_args *argv)
 
-/* Declare a prototype, then begin the implementation of the function
-   "<NAME>_LTX_m4_init_module", which will automatically be registered
-   as the initialization function for module NAME.  Note that NAME is
-   intentionally used literally, rather than subjected to macro
-   expansion.  */
-#define M4INIT_HANDLER(name)                                            \
-  void name ## _LTX_m4_init_module                                      \
-    (m4 *, m4_module *, m4_obstack *);                                  \
-  void name ## _LTX_m4_init_module                                      \
-    (m4 *context, m4_module *module, m4_obstack *obs)
-
 /* Declare a variable S of type "<S>_func" to be a pointer to the
    function named S imported from the module M, or NULL if the import
    fails.  Note that M and S are intentionally used literally rather
diff --git a/m4/m4private.h b/m4/m4private.h
index 926df58f..452496da 100644
--- a/m4/m4private.h
+++ b/m4/m4private.h
@@ -22,7 +22,6 @@
 #define M4PRIVATE_H 1
 
 #include <m4/m4module.h>
-#include <ltdl.h>
 
 #include "cloexec.h"
 #include "quotearg.h"
@@ -175,20 +174,17 @@ extern void m4__builtin_print (m4_obstack *, const m4__builtin *, bool,
 
 /* --- MODULE MANAGEMENT --- */
 
-#define INIT_SYMBOL             "m4_init_module"
-
 /* Representation of a loaded m4 module.  */
 struct m4_module
 {
   const char *name;             /* Name of the module.  */
-  lt_dlhandle handle;           /* All ltdl module information.  */
+  void *handle;                 /* System module handle.  */
   m4__builtin *builtins;        /* Sorted array of builtins.  */
   m4_macro *macros;		/* Unsorted array of macros.  */
   size_t builtins_len;          /* Number of builtins.  */
   m4_module *next;
 };
 
-extern void         m4__module_init (m4 *context);
 extern m4_module *  m4__module_open (m4 *context, const char *name,
                                      m4_obstack *obs);
 extern m4_module *  m4__module_find (m4 *context, const char *name);
diff --git a/m4/module.c b/m4/module.c
index 39cd2d23..6f2a2a9e 100644
--- a/m4/module.c
+++ b/m4/module.c
@@ -20,6 +20,8 @@
 
 #include <config.h>
 
+#include <dlfcn.h>
+
 #include "m4private.h"
 #include "xvasprintf.h"
 
@@ -71,10 +73,6 @@ static void         install_builtin_table (m4*, m4_module *);
 static void         install_macro_table   (m4*, m4_module *);
 
 static int          compare_builtin_CB    (const void *a, const void *b);
-static int          m4__module_interface  (lt_dlhandle handle,
-                                           const char *id_string);
-
-static lt_dlinterface_id iface_id = NULL;
 
 const char *
 m4_get_module_name (const m4_module *module)
@@ -99,7 +97,7 @@ m4_module_import (m4 *context, const char *module_name,
 
   if (module)
     {
-      symbol_address = lt_dlsym (module->handle, symbol_name);
+      symbol_address = dlsym (module->handle, symbol_name);
 
       if (!symbol_address)
         m4_error (context, 0, 0, NULL,
@@ -230,21 +228,6 @@ m4_module_load (m4 *context, const char *name, m4_obstack *obs)
   return module;
 }
 
-
-static int
-m4__module_interface (lt_dlhandle handle, const char *id_string)
-{
-  /* Shortcut.  If we've already associated our wrapper with this
-     handle, then we've validated the handle in the past, and don't
-     need to waste any time on additional lt_dlsym calls.  */
-  m4_module *module = (m4_module *) lt_dlcaller_get_data (iface_id, handle);
-  if (module)
-    return 0;
-
-  /* A valid m4 module must provide at least one of these symbols.  */
-  return !(lt_dlsym (handle, INIT_SYMBOL));
-}
-
 
 /* Return successive loaded modules. */
 m4_module *
@@ -263,56 +246,6 @@ m4__module_find (m4 *context, const char *name)
 }
 
 
-/* Initialization.  Currently the module search path in path.c is
-   initialized from M4MODPATH.  Only absolute path names are accepted to
-   prevent the path search of the dlopen library from finding wrong
-   files. */
-void
-m4__module_init (m4 *context)
-{
-  int errors = 0;
-
-  /* Do this only once!  If we already have an iface_id, then the
-     module system has already been initialized.  */
-  if (iface_id)
-    {
-      m4_error (context, 0, 0, NULL,
-                _("multiple module loader initializations"));
-      return;
-    }
-
-  errors      = lt_dlinit ();
-
-  /* Register with libltdl for a key to store client data against
-     ltdl module handles.  */
-  if (!errors)
-    {
-      iface_id = lt_dlinterface_register ("m4 libm4", m4__module_interface);
-
-      if (!iface_id)
-        {
-          const char *error_msg = _("libltdl client registration failed");
-
-          lt_dlseterror (lt_dladderror (error_msg));
-
-          /* No need to check error statuses from the calls above -- If
-             either fails for some reason, a diagnostic will be set for
-             lt_dlerror() anyway.  */
-          ++errors;
-        }
-    }
-
-  /* Couldn't initialize the module system; diagnose and exit.  */
-  if (errors)
-    m4_error (context, EXIT_FAILURE, 0, NULL,
-              _("failed to initialize module loader: %s"), module_dlerror ());
-
-#ifdef DEBUG_MODULES
-  fputs ("Module loader initialized.\n", stderr);
-#endif /* DEBUG_MODULES */
-}
-
-
 /* Compare two builtins A and B for sorting, as in qsort.  */
 static int
 compare_builtin_CB (const void *a, const void *b)
@@ -332,95 +265,53 @@ compare_builtin_CB (const void *a, const void *b)
 m4_module *
 m4__module_open (m4 *context, const char *name, m4_obstack *obs)
 {
-  static const char *	suffixes[]	= { "", ".la", LT_MODULE_EXT, NULL };
-  char *		filepath	= NULL;
-  lt_dlhandle		handle		= NULL;
-  lt_dladvise		advise		= NULL;
+  static const char *	suffixes[]	= { "", ".so", NULL };
   m4_module *		module		= NULL;
-  m4_module_init_func *	init_func	= NULL;
 
   assert (context);
-  assert (iface_id);            /* need to have called m4__module_init */
 
-  /* Try opening as a preloaded module initially incase path searching
-     has been disabled by POSIXLY_CORRECT... */
-  if (!lt_dladvise_init (&advise) && !lt_dladvise_preload (&advise))
-    handle = lt_dlopenadvise (name, advise);
-  lt_dladvise_destroy (&advise);
+  char *filepath = m4_path_search (context, name, suffixes);
+  void *handle   = NULL;
 
-  /* ...otherwise resort to a path search anyway.  */
-  if (!handle)
+  if (filepath)
     {
-      filepath = m4_path_search (context, name, suffixes);
-      if (filepath)
-        {
-          handle = lt_dlopenext (filepath);
-          free (filepath);
-        }
+      handle = dlopen (filepath, RTLD_NOW|RTLD_GLOBAL);
+      free (filepath);
     }
 
   if (handle)
     {
-      const lt_dlinfo *info = lt_dlgetinfo (handle);
-
-      /* If we have a handle, there must be handle info.  */
-      assert (info);
-
-#ifdef DEBUG_MODULES
-      if (info->ref_count > 1)
-        {
-          xfprintf (stderr, "module %s: now has %d libtool references.",
-                    name, info->ref_count);
-        }
-#endif /* DEBUG_MODULES */
-
       m4_debug_message (context, M4_DEBUG_TRACE_MODULE,
                         _("module %s: opening file %s"),
                         name ? name : MODULE_SELF_NAME,
-                        quotearg_style (locale_quoting_style, info->filename));
+                        quotearg_style (locale_quoting_style, name));
+
+      module = (m4_module *) xzalloc (sizeof *module);
+      module->name   = xstrdup (name);
+      module->handle = handle;
+      module->next   = context->modules;
 
-      /* Provide the m4_module corresponding to the lt_dlhandle, if
-         not yet created.  */
-      module = (m4_module *) lt_dlcaller_get_data (iface_id, handle);
-      if (!module)
+      context->modules = module;
+      m4_hash_insert (context->namemap, xstrdup (name), module);
+
+      /* Find and run any initializing function in the opened module,
+         the first time the module is opened.  */
+      char *entry_point = xasprintf ("include_%s", name);
+      m4_module_init_func *init_func =
+          (m4_module_init_func *) dlsym (handle, entry_point);
+      free (entry_point);
+
+      if (init_func)
+        {
+          init_func (context, module, obs);
+
+          m4_debug_message (context, M4_DEBUG_TRACE_MODULE,
+                            _("module %s: init hook called"), name);
+        }
+      else
         {
-          void *old;
-          const char *err;
-
-          module = (m4_module *) xzalloc (sizeof *module);
-          module->name   = xstrdup (name);
-          module->handle = handle;
-	  module->next   = context->modules;
-
-	  context->modules = module;
-	  m4_hash_insert (context->namemap, xstrdup (name), module);
-
-          /* clear out any stale errors, since we have to use
-             lt_dlerror to distinguish between success and
-             failure.  */
-          lt_dlerror ();
-          old = lt_dlcaller_set_data (iface_id, handle, module);
-          assert (!old);
-          err = lt_dlerror ();
-          if (err)
-            m4_error (context, EXIT_FAILURE, 0, NULL,
-                      _("unable to load module `%s': %s"), name, err);
-
-          /* Find and run any initializing function in the opened module,
-             the first time the module is opened.  */
-          init_func = (m4_module_init_func *) lt_dlsym (handle, INIT_SYMBOL);
-          if (init_func)
-            {
-              init_func (context, module, obs);
-
-              m4_debug_message (context, M4_DEBUG_TRACE_MODULE,
-                                _("module %s: init hook called"), name);
-            }
-          else
-            {
-              m4_error (context, EXIT_FAILURE, 0, NULL,
-                        _("module `%s' has no entry point"), name);
-            }
+          m4_error (context, EXIT_FAILURE, 0, NULL,
+                    _("module `%s' has no entry point"), name);
         }
 
       m4_debug_message (context, M4_DEBUG_TRACE_MODULE,
@@ -428,23 +319,13 @@ m4__module_open (m4 *context, const char *name, m4_obstack *obs)
     }
   else
     {
+      const char *err = dlerror ();
+      if (!err) err = _("unknown error");
+
       /* Couldn't open the module; diagnose and exit. */
       m4_error (context, EXIT_FAILURE, 0, NULL,
-                _("cannot open module `%s': %s"), name, module_dlerror ());
+                _("cannot open module `%s': %s"), name, err);
     }
 
   return module;
 }
-
-
-/* FIXME - libtool doesn't expose lt_dlerror strings for translation.  */
-static const char *
-module_dlerror (void)
-{
-  const char *dlerror = lt_dlerror ();
-
-  if (!dlerror)
-    dlerror = _("unknown error");
-
-  return dlerror;
-}
diff --git a/m4/path.c b/m4/path.c
index 9437e936..3a932897 100644
--- a/m4/path.c
+++ b/m4/path.c
@@ -41,8 +41,7 @@ static const char *FILE_SUFFIXES[] = {
   "",
   ".m4f",
   ".m4",
-  ".la",
-  LT_MODULE_EXT,
+  ".so",
   NULL
 };
 
@@ -297,7 +296,7 @@ m4_load_filename (m4 *context, const m4_call_info *caller,
 
   if (!m4_get_posixly_correct_opt (context)
       && suffix
-      && (STREQ (suffix, LT_MODULE_EXT) || STREQ (suffix, ".la")))
+      && STREQ (suffix, ".so"))
     {
       m4_module_load (context, filename, obs);
     }
diff --git a/modules/gnu.c b/modules/gnu.c
index 96c75475..874502e0 100644
--- a/modules/gnu.c
+++ b/modules/gnu.c
@@ -97,7 +97,8 @@ static const m4_macro m4_macro_table[] =
 };
 
 
-M4INIT_HANDLER (gnu)
+void
+include_gnu (m4 *context, m4_module *module, m4_obstack *obs)
 {
   m4_install_builtins (context, module, m4_builtin_table);
   m4_install_macros   (context, module, m4_macro_table);
diff --git a/modules/import.c b/modules/import.c
index 679a50d5..9f03493c 100644
--- a/modules/import.c
+++ b/modules/import.c
@@ -28,9 +28,6 @@
 #  include "m4private.h"
 #endif
 
-/* Rename exported symbols for dlpreload()ing.  */
-#define m4_builtin_table        import_LTX_m4_builtin_table
-
 /*         function     macros  blind   side    minargs maxargs */
 #define builtin_functions                                       \
   BUILTIN (import,      false,  false,  false,  0,      1)      \
@@ -53,7 +50,8 @@ static const m4_builtin m4_builtin_table[] =
 };
 
 
-M4INIT_HANDLER (import)
+void
+include_import (m4 *context, m4_module *module, m4_obstack *obs)
 {
   m4_install_builtins (context, module, m4_builtin_table);
 }
diff --git a/modules/m4.c b/modules/m4.c
index ecae4c3a..ec47d01c 100644
--- a/modules/m4.c
+++ b/modules/m4.c
@@ -38,13 +38,6 @@
 
 #include <modules/m4.h>
 
-/* Rename exported symbols for dlpreload()ing.  */
-#define m4_set_sysval           m4_LTX_m4_set_sysval
-#define m4_sysval_flush         m4_LTX_m4_sysval_flush
-#define m4_dump_symbols         m4_LTX_m4_dump_symbols
-#define m4_expand_ranges        m4_LTX_m4_expand_ranges
-#define m4_make_temp            m4_LTX_m4_make_temp
-
 extern void m4_set_sysval    (int);
 extern void m4_sysval_flush  (m4 *, bool);
 extern void m4_dump_symbols  (m4 *, m4_dump_symbol_data *, size_t,
@@ -113,7 +106,7 @@ static void     numb_obstack    (m4_obstack *obs, number value,
 
 
 /* Generate a table for mapping m4 symbol names to handler functions. */
-const m4_builtin m4_builtin_table[] =
+static const m4_builtin m4_builtin_table[] =
 {
 #define BUILTIN(handler, macros, blind, side, min, max)                 \
   M4BUILTIN_ENTRY (handler, #handler, macros, blind, side, min, max)
@@ -125,7 +118,8 @@ const m4_builtin m4_builtin_table[] =
 };
 
 
-M4INIT_HANDLER (m4)
+void
+include_m4 (m4 *context, m4_module *module, m4_obstack *obs)
 {
   m4_install_builtins (context, module, m4_builtin_table);
 }
diff --git a/modules/modtest.c b/modules/modtest.c
index 75450f7e..2026431d 100644
--- a/modules/modtest.c
+++ b/modules/modtest.c
@@ -28,9 +28,6 @@
 #  include "m4private.h"
 #endif
 
-/* Rename exported symbols for dlpreload()ing.  */
-#define export_test             modtest_LTX_export_test
-
 extern bool export_test (const char *foo);
 
 /*         function     macros  blind   side    minargs maxargs */
@@ -66,7 +63,8 @@ static const m4_macro m4_macro_table[] =
 /**
  * modtest()
  **/
-M4INIT_HANDLER (modtest)
+void
+include_modtest (m4 *context, m4_module *module, m4_obstack *obs)
 {
   const char *s = "Test module loaded.\n";
 
diff --git a/modules/mpeval.c b/modules/mpeval.c
index 49afd765..4debc99d 100644
--- a/modules/mpeval.c
+++ b/modules/mpeval.c
@@ -122,7 +122,8 @@ static const m4_macro m4_macro_table[] =
 };
 
 
-M4INIT_HANDLER (mpeval)
+void
+include_mpeval (m4 *context, m4_module *module, m4_obstack *obs)
 {
   m4_install_builtins (context, module, m4_builtin_table);
   m4_install_macros   (context, module, m4_macro_table);
diff --git a/modules/shadow.c b/modules/shadow.c
index 53829937..2247f397 100644
--- a/modules/shadow.c
+++ b/modules/shadow.c
@@ -58,7 +58,8 @@ static const m4_macro m4_macro_table[] =
 
 
 
-M4INIT_HANDLER (shadow)
+void
+include_shadow (m4 *context, m4_module *module, m4_obstack *obs)
 {
   const char *s = "Shadow module loaded.";
 
diff --git a/modules/stdlib.c b/modules/stdlib.c
index b01326df..5a300d65 100644
--- a/modules/stdlib.c
+++ b/modules/stdlib.c
@@ -70,7 +70,8 @@ static const m4_builtin m4_builtin_table[] =
 };
 
 
-M4INIT_HANDLER (stdlib)
+void
+include_stdlib (m4 *context, m4_module *module, m4_obstack *obs)
 {
   m4_install_builtins (context, module, m4_builtin_table);
 }
diff --git a/modules/time.c b/modules/time.c
index 39db75fe..5c9c2ce6 100644
--- a/modules/time.c
+++ b/modules/time.c
@@ -76,7 +76,8 @@ static const m4_builtin m4_builtin_table[] =
 };
 
 
-M4INIT_HANDLER (time)
+void
+include_time (m4 *context, m4_module *module, m4_obstack *obs)
 {
   m4_install_builtins (context, module, m4_builtin_table);
 }
diff --git a/modules/traditional.c b/modules/traditional.c
index 88a4966b..f9cb9501 100644
--- a/modules/traditional.c
+++ b/modules/traditional.c
@@ -45,7 +45,8 @@ static const m4_macro m4_macro_table[] =
   { NULL,               NULL,   0,      0 },
 };
 
-M4INIT_HANDLER (traditional)
+void
+include_traditional (m4 *context, m4_module *module, m4_obstack *obs)
 {
   m4_install_macros (context, module, m4_macro_table);
 }
diff --git a/src/main.c b/src/main.c
index 53305451..27d6dc8e 100644
--- a/src/main.c
+++ b/src/main.c
@@ -331,12 +331,8 @@ main (int argc, char *const *argv, char *const *envp)
   textdomain (PACKAGE);
 #endif
 
-  LTDL_SET_PRELOADED_SYMBOLS ();
-
   context = m4_create ();
 
-  m4__module_init (context);
-
 #ifdef USE_STACKOVF
   setup_stackovf_trap (argv, envp, stackovf_handler);
 #endif
diff --git a/tests/m4.in b/tests/m4.in
index 2a9b7f3f..e93b0b99 100644
--- a/tests/m4.in
+++ b/tests/m4.in
@@ -34,7 +34,13 @@ else
   case `(set -o) 2>/dev/null` in *posix*) set -o posix;; esac
 fi
 
+M4PATH="\
+@abs_top_builddir@/modules/.libs:\
+@abs_top_builddir@/tests/.libs:\
+${M4PATH+$M4PATH:}\
+:"
+export M4PATH
+
 exec "@abs_top_builddir@/src/m4" \
-      --include="@abs_top_builddir@/modules" \
       ${1+"$@"}
 exit 1