[RFA v2 04/17] Introduce gdb_dlhandle_up

Tom Tromey
2017-04-11T15:01:42Z

This introduces gdb_dlhandle_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.

gdb/ChangeLog
2017-04-11 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_dlhandle_up): New typedef.
(gdb_dlopen, gdb_dlsym): Update types.
(gdb_dlclose): Remove.
* gdb-dlfcn.c (gdb_dlopen): Return a gdb_dlhandle_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 a71de4a..a888174 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,22 @@
2017-04-11 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_dlhandle_up): New typedef.
+ (gdb_dlopen, gdb_dlsym): Update types.
+ (gdb_dlclose): Remove.
+ * gdb-dlfcn.c (gdb_dlopen): Return a gdb_dlhandle_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.
+
+2017-04-11 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..2614570 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_dlhandle_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..7485a38 100644
--- a/gdb/gdb-dlfcn.c
+++ b/gdb/gdb-dlfcn.c
@@ -31,27 +31,20 @@

#ifdef NO_SHARED_LIB

-void *
+gdb_dlhandle_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_dlhandle_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_dlhandle_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_dlhandle_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_dlhandle_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..021f759 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_dlhandle_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_dlhandle_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_dlhandle_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..ddf1005 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_dlhandle_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_dlhandle_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_dlhandle_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