[RFA 04/14] Introduce gdb_dlopen_up

[Tom Tromey <tom at tromey dot com>]

This introduces gdb_dlopen_up, a unique_ptr that can close a dlopen'd
library.  All the functions working with dlopen handles are updated to
use this new type.

I did not try to build this on Windows.

2017-04-07  Tom Tromey  <tom@tromey.com>

	* jit.c (struct jit_reader): Declare separately.  Add constructor
	and destructor.  Change type of "handle".
	(loaded_jit_reader): Define separately.
	(jit_reader_load): Update.  New "new".
	(jit_reader_unload_command): Use "delete".
	* gdb-dlfcn.h (struct dlclose_deleter): New.
	(gdb_dlopen_up): New typedef.
	(gdb_dlopen, gdb_dlsym): Update types.
	(gdb_dlclose): Remove.
	* gdb-dlfcn.c (gdb_dlopen): Return a gdb_dlopen_up.
	(gdb_dlsym): Change type of "handle".
	(make_cleanup_dlclose): Remove.
	(dlclose_deleter::operator()): Rename from gdb_dlclose.
	* compile/compile-c-support.c (load_libcc): Update.
---
 gdb/ChangeLog                   | 17 ++++++++++++++++
 gdb/compile/compile-c-support.c |  6 ++++--
 gdb/gdb-dlfcn.c                 | 45 ++++++++++++-----------------------------
 gdb/gdb-dlfcn.h                 | 24 ++++++++++++----------
 gdb/jit.c                       | 42 +++++++++++++++++++++-----------------
 5 files changed, 70 insertions(+), 64 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 9451af1..296030c 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,22 @@
 2017-04-07  Tom Tromey  <tom@tromey.com>
 
+	* jit.c (struct jit_reader): Declare separately.  Add constructor
+	and destructor.  Change type of "handle".
+	(loaded_jit_reader): Define separately.
+	(jit_reader_load): Update.  New "new".
+	(jit_reader_unload_command): Use "delete".
+	* gdb-dlfcn.h (struct dlclose_deleter): New.
+	(gdb_dlopen_up): New typedef.
+	(gdb_dlopen, gdb_dlsym): Update types.
+	(gdb_dlclose): Remove.
+	* gdb-dlfcn.c (gdb_dlopen): Return a gdb_dlopen_up.
+	(gdb_dlsym): Change type of "handle".
+	(make_cleanup_dlclose): Remove.
+	(dlclose_deleter::operator()): Rename from gdb_dlclose.
+	* compile/compile-c-support.c (load_libcc): Update.
+
+2017-04-07  Tom Tromey  <tom@tromey.com>
+
 	* symtab.h (find_pcs_for_symtab_line): Change return type.
 	* symtab.c (find_pcs_for_symtab_line): Change return type.
 	* python/py-linetable.c (build_line_table_tuple_from_pcs): Change
diff --git a/gdb/compile/compile-c-support.c b/gdb/compile/compile-c-support.c
index c969b42..a10296a 100644
--- a/gdb/compile/compile-c-support.c
+++ b/gdb/compile/compile-c-support.c
@@ -75,12 +75,11 @@ c_get_range_decl_name (const struct dynamic_prop *prop)
 static gcc_c_fe_context_function *
 load_libcc (void)
 {
-  void *handle;
   gcc_c_fe_context_function *func;
 
    /* gdb_dlopen will call error () on an error, so no need to check
       value.  */
-  handle = gdb_dlopen (STRINGIFY (GCC_C_FE_LIBCC));
+  gdb_dlopen_up handle = gdb_dlopen (STRINGIFY (GCC_C_FE_LIBCC));
   func = (gcc_c_fe_context_function *) gdb_dlsym (handle,
 						  STRINGIFY (GCC_C_FE_CONTEXT));
 
@@ -88,6 +87,9 @@ load_libcc (void)
     error (_("could not find symbol %s in library %s"),
 	   STRINGIFY (GCC_C_FE_CONTEXT),
 	   STRINGIFY (GCC_C_FE_LIBCC));
+
+  /* Leave the library open.  */
+  handle.release ();
   return func;
 }
 
diff --git a/gdb/gdb-dlfcn.c b/gdb/gdb-dlfcn.c
index a11e396..11571d6 100644
--- a/gdb/gdb-dlfcn.c
+++ b/gdb/gdb-dlfcn.c
@@ -31,27 +31,20 @@
 
 #ifdef NO_SHARED_LIB
 
-void *
+gdb_dlopen_up
 gdb_dlopen (const char *filename)
 {
   gdb_assert_not_reached ("gdb_dlopen should not be called on this platform.");
 }
 
 void *
-gdb_dlsym (void *handle, const char *symbol)
+gdb_dlsym (const gdb_dlopen_up &handle, const char *symbol)
 {
   gdb_assert_not_reached ("gdb_dlsym should not be called on this platform.");
 }
 
-struct cleanup *
-make_cleanup_dlclose (void *handle)
-{
-  gdb_assert_not_reached ("make_cleanup_dlclose should not be called on this "
-                          "platform.");
-}
-
-int
-gdb_dlclose (void *handle)
+void
+dlclose_deleter::operator() (void *handle) const
 {
   gdb_assert_not_reached ("gdb_dlclose should not be called on this platform.");
 }
@@ -64,7 +57,7 @@ is_dl_available (void)
 
 #else /* NO_SHARED_LIB */
 
-void *
+gdb_dlopen_up
 gdb_dlopen (const char *filename)
 {
   void *result;
@@ -74,7 +67,7 @@ gdb_dlopen (const char *filename)
   result = (void *) LoadLibrary (filename);
 #endif
   if (result != NULL)
-    return result;
+    return gdb_dlopen_up (result);
 
 #ifdef HAVE_DLFCN_H
   error (_("Could not load %s: %s"), filename, dlerror());
@@ -97,37 +90,25 @@ gdb_dlopen (const char *filename)
 }
 
 void *
-gdb_dlsym (void *handle, const char *symbol)
+gdb_dlsym (const gdb_dlopen_up &handle, const char *symbol)
 {
 #ifdef HAVE_DLFCN_H
-  return dlsym (handle, symbol);
+  return dlsym (handle.get (), symbol);
 #elif __MINGW32__
-  return (void *) GetProcAddress ((HMODULE) handle, symbol);
+  return (void *) GetProcAddress ((HMODULE) handle.get (), symbol);
 #endif
 }
 
-int
-gdb_dlclose (void *handle)
+void
+dlclose_deleter::operator() (void *handle) const
 {
 #ifdef HAVE_DLFCN_H
-  return dlclose (handle);
+  dlclose (handle);
 #elif __MINGW32__
-  return !((int) FreeLibrary ((HMODULE) handle));
+  FreeLibrary ((HMODULE) handle);
 #endif
 }
 
-static void
-do_dlclose_cleanup (void *handle)
-{
-  gdb_dlclose (handle);
-}
-
-struct cleanup *
-make_cleanup_dlclose (void *handle)
-{
-  return make_cleanup (do_dlclose_cleanup, handle);
-}
-
 int
 is_dl_available (void)
 {
diff --git a/gdb/gdb-dlfcn.h b/gdb/gdb-dlfcn.h
index 31709a9..a9435ed 100644
--- a/gdb/gdb-dlfcn.h
+++ b/gdb/gdb-dlfcn.h
@@ -20,26 +20,28 @@
 #ifndef GDB_DLFCN_H
 #define GDB_DLFCN_H
 
+/* A deleter that closes an open dynamic library.  */
+
+struct dlclose_deleter
+{
+  void operator() (void *handle) const;
+};
+
+/* A unique pointer that points to a dynamic library.  */
+
+typedef std::unique_ptr<void, dlclose_deleter> gdb_dlopen_up;
+
 /* Load the dynamic library file named FILENAME, and return a handle
    for that dynamic library.  Return NULL if the loading fails for any
    reason.  */
 
-void *gdb_dlopen (const char *filename);
+gdb_dlopen_up gdb_dlopen (const char *filename);
 
 /* Return the address of the symbol named SYMBOL inside the shared
    library whose handle is HANDLE.  Return NULL when the symbol could
    not be found.  */
 
-void *gdb_dlsym (void *handle, const char *symbol);
-
-/* Install a cleanup routine which closes the handle HANDLE.  */
-
-struct cleanup *make_cleanup_dlclose (void *handle);
-
-/* Cleanup the shared object pointed to by HANDLE. Return 0 on success
-   and nonzero on failure.  */
-
-int gdb_dlclose (void *handle);
+void *gdb_dlsym (const gdb_dlopen_up &handle, const char *symbol);
 
 /* Return non-zero if the dynamic library functions are available on
    this platform.  */
diff --git a/gdb/jit.c b/gdb/jit.c
index 158d6d8..7523a46 100644
--- a/gdb/jit.c
+++ b/gdb/jit.c
@@ -151,14 +151,29 @@ bfd_open_from_target_memory (CORE_ADDR addr, ULONGEST size, char *target)
 			      mem_bfd_iovec_stat);
 }
 
+struct jit_reader
+{
+  jit_reader (struct gdb_reader_funcs *f, gdb_dlopen_up &&h)
+    : functions (f), handle (std::move (h))
+  {
+  }
+
+  ~jit_reader ()
+  {
+    functions->destroy (functions);
+  }
+
+  jit_reader (const jit_reader &) = delete;
+  jit_reader &operator= (const jit_reader &) = delete;
+
+  struct gdb_reader_funcs *functions;
+  gdb_dlopen_up handle;
+};
+
 /* One reader that has been loaded successfully, and can potentially be used to
    parse debug info.  */
 
-static struct jit_reader
-{
-  struct gdb_reader_funcs *functions;
-  void *handle;
-} *loaded_jit_reader = NULL;
+static struct jit_reader *loaded_jit_reader = NULL;
 
 typedef struct gdb_reader_funcs * (reader_init_fn_type) (void);
 static const char *reader_init_fn_sym = "gdb_init_reader";
@@ -168,17 +183,13 @@ static const char *reader_init_fn_sym = "gdb_init_reader";
 static struct jit_reader *
 jit_reader_load (const char *file_name)
 {
-  void *so;
   reader_init_fn_type *init_fn;
-  struct jit_reader *new_reader = NULL;
   struct gdb_reader_funcs *funcs = NULL;
-  struct cleanup *old_cleanups;
 
   if (jit_debug)
     fprintf_unfiltered (gdb_stdlog, _("Opening shared object %s.\n"),
                         file_name);
-  so = gdb_dlopen (file_name);
-  old_cleanups = make_cleanup_dlclose (so);
+  gdb_dlopen_up so = gdb_dlopen (file_name);
 
   init_fn = (reader_init_fn_type *) gdb_dlsym (so, reader_init_fn_sym);
   if (!init_fn)
@@ -192,12 +203,7 @@ jit_reader_load (const char *file_name)
   if (funcs->reader_version != GDB_READER_INTERFACE_VERSION)
     error (_("Reader version does not match GDB version."));
 
-  new_reader = XCNEW (struct jit_reader);
-  new_reader->functions = funcs;
-  new_reader->handle = so;
-
-  discard_cleanups (old_cleanups);
-  return new_reader;
+  return new jit_reader (funcs, std::move (so));
 }
 
 /* Provides the jit-reader-load command.  */
@@ -240,10 +246,8 @@ jit_reader_unload_command (char *args, int from_tty)
 
   reinit_frame_cache ();
   jit_inferior_exit_hook (current_inferior ());
-  loaded_jit_reader->functions->destroy (loaded_jit_reader->functions);
 
-  gdb_dlclose (loaded_jit_reader->handle);
-  xfree (loaded_jit_reader);
+  delete loaded_jit_reader;
   loaded_jit_reader = NULL;
 }
 
-- 
2.9.3