[PATCH v2 12/36] Guile extension language: scm-gsmob.c
Doug Evans
xdje42@gmail.com
Mon Jan 20 21:53:00 GMT 2014
This patch adds the low level support for using Guile "smobs".
Smobs are used throughout the port to implement the interface
between C and Guile.
Changes from v1:
- scm-smob.c renamed to scm-gsmob.c
- change "aux" field of gsmobs to a property list/table
- remove *scm->smob*, *smob->scm*: I was playing with it and wasn't
sure enough that it's a reasonable way to go, so it's left out for now
- all gsmobs updated to remove this functionality
2014-01-20 Doug Evans <xdje42@gmail.com>
* guile/scm-gsmob.c: New file.
diff --git a/gdb/guile/scm-gsmob.c b/gdb/guile/scm-gsmob.c
new file mode 100644
index 0000000..5f9e856
--- /dev/null
+++ b/gdb/guile/scm-gsmob.c
@@ -0,0 +1,486 @@
+/* GDB/Scheme smobs (gsmob is pronounced "jee smob")
+
+ Copyright (C) 2014 Free Software Foundation, Inc.
+
+ This file is part of GDB.
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR 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/>. */
+
+/* See README file in this directory for implementation notes, coding
+ conventions, et.al. */
+
+/* Smobs are Guile's "small object".
+ They are used to export C structs to Scheme.
+
+ Note: There's only room in the encoding space for 256, and while we won't
+ come close to that, mixed with other libraries maybe someday we could.
+ We don't worry about it now, except to be aware of the issue.
+ We could allocate just a few smobs and use the unused smob flags field to
+ specify the gdb smob kind, that is left for another day if it ever is
+ needed.
+
+ We want the objects we export to Scheme to be extensible by the user.
+ A gsmob (gdb smob) adds a simple API on top of smobs to support this.
+ This allows GDB objects to be easily extendable in a useful manner.
+ To that end, all smobs in gdb have gdb_smob as the first member.
+
+ On top of gsmobs there are "chained gsmobs". They are used to assist with
+ life-time tracking of GDB objects vs Scheme objects. Gsmobs can "subclass"
+ chained_gdb_smob, which contains a doubly-linked list to assist with
+ life-time tracking.
+
+ On top of gsmobs there are also "eqable gsmobs". Gsmobs can "subclass"
+ eqable_gdb_smob instead of gdb_smob, and is used to make gsmobs eq?-able.
+ This is done by recording all gsmobs in a hash table and before creating a
+ gsmob first seeing if it's already in the table. Eqable gsmobs can also be
+ used where lifetime-tracking is required.
+
+ Gsmobs (and chained/eqable gsmobs) add an extra field that is used to
+ record extra data: "properties". It is a table of key/value pairs
+ that can be set with set-gsmob-property!, gsmob-property. */
+
+#include "defs.h"
+#include "hashtab.h"
+#include "gdb_assert.h"
+#include "objfiles.h"
+#include "guile-internal.h"
+
+/* We need to call this. Undo our hack to prevent others from calling it. */
+#undef scm_make_smob_type
+
+static htab_t registered_gsmobs;
+
+/* Gsmob properties are initialize stored as an alist to minimize space
+ usage: GDB can be used to debug some really big programs, and property
+ lists generally have very few elements. Once the list grows to this
+ many elements then we switch to a hash table.
+ The smallest Guile hashtable in 2.0 uses a vector of 31 elements.
+ The value we use here is large enough to hold several expected uses,
+ without being so large that we might as well just use a hashtable. */
+#define SMOB_PROP_HTAB_THRESHOLD 7
+
+/* Hash function for registered_gsmobs hash table. */
+
+static hashval_t
+hash_scm_t_bits (const void *item)
+{
+ uintptr_t v = (uintptr_t) item;
+
+ return v;
+}
+
+/* Equality function for registered_gsmobs hash table. */
+
+static int
+eq_scm_t_bits (const void *item_lhs, const void *item_rhs)
+{
+ return item_lhs == item_rhs;
+}
+
+/* Record GSMOB_CODE as being a gdb smob.
+ GSMOB_CODE is the result of scm_make_smob_type. */
+
+static void
+register_gsmob (scm_t_bits gsmob_code)
+{
+ void **slot;
+
+ slot = htab_find_slot (registered_gsmobs, (void *) gsmob_code, INSERT);
+ gdb_assert (*slot == NULL);
+ *slot = (void *) gsmob_code;
+}
+
+/* Return non-zero if SCM is any registered gdb smob object. */
+
+static int
+gdbscm_is_gsmob (SCM scm)
+{
+ void **slot;
+
+ if (SCM_IMP (scm))
+ return 0;
+ slot = htab_find_slot (registered_gsmobs, (void *) SCM_TYP16 (scm),
+ NO_INSERT);
+ return slot != NULL;
+}
+
+/* Call this to register a smob, instead of scm_make_smob_type. */
+
+scm_t_bits
+gdbscm_make_smob_type (const char *name, size_t size)
+{
+ scm_t_bits result = scm_make_smob_type (name, size);
+
+ register_gsmob (result);
+ return result;
+}
+
+/* Initialize a gsmob. */
+
+void
+gdbscm_init_gsmob (gdb_smob *base)
+{
+ base->properties = SCM_EOL;
+}
+
+/* Initialize a chained_gdb_smob.
+ This is the same as gdbscm_init_gsmob except that it also sets prev,next
+ to NULL. */
+
+void
+gdbscm_init_chained_gsmob (chained_gdb_smob *base)
+{
+ gdbscm_init_gsmob ((gdb_smob *) base);
+ base->prev = NULL;
+ base->next = NULL;
+}
+
+/* Initialize an eqable_gdb_smob.
+ This is the same as gdbscm_init_gsmob except that it also sets
+ containing_scm to #f. */
+
+void
+gdbscm_init_eqable_gsmob (eqable_gdb_smob *base)
+{
+ gdbscm_init_gsmob ((gdb_smob *) base);
+ base->containing_scm = SCM_BOOL_F;
+}
+
+/* Call this from each smob's "mark" routine.
+ In general, this should be called as:
+ return gdbscm_mark_gsmob (base); */
+
+SCM
+gdbscm_mark_gsmob (gdb_smob *base)
+{
+ /* Return the last one to mark as an optimization.
+ The marking infrastructure will mark it for us. */
+ return base->properties;
+}
+
+/* Call this from each smob's "mark" routine.
+ In general, this should be called as:
+ return gdbscm_mark_chained_gsmob (base); */
+
+SCM
+gdbscm_mark_chained_gsmob (chained_gdb_smob *base)
+{
+ /* Return the last one to mark as an optimization.
+ The marking infrastructure will mark it for us. */
+ return base->properties;
+}
+
+/* Call this from each smob's "mark" routine.
+ In general, this should be called as:
+ return gdbscm_mark_eqable_gsmob (base); */
+
+SCM
+gdbscm_mark_eqable_gsmob (eqable_gdb_smob *base)
+{
+ /* There's no need to mark containing_scm.
+ Any references to it either come from Scheme in which case it will be
+ marked through them, or there's a reference to the smob from gdb in
+ which case the smob is GC-protected. */
+
+ /* Return the last one to mark as an optimization.
+ The marking infrastructure will mark it for us. */
+ return base->properties;
+}
+
+/* gsmob accessors */
+
+/* Return the gsmob in SELF.
+ Throws an exception if SELF is not a gsmob. */
+
+static SCM
+gsscm_get_gsmob_arg_unsafe (SCM self, int arg_pos, const char *func_name)
+{
+ SCM_ASSERT_TYPE (gdbscm_is_gsmob (self), self, arg_pos, func_name,
+ _("any gdb smob"));
+
+ return self;
+}
+
+/* (gsmob-kind gsmob) -> symbol
+
+ Note: While one might want to name this gsmob-class-name, it is named
+ "-kind" because smobs aren't real GOOPS classes. */
+
+static SCM
+gdbscm_gsmob_kind (SCM self)
+{
+ SCM smob, result;
+ scm_t_bits smobnum;
+ const char *name;
+ char *kind;
+
+ smob = gsscm_get_gsmob_arg_unsafe (self, SCM_ARG1, FUNC_NAME);
+
+ smobnum = SCM_SMOBNUM (smob);
+ name = SCM_SMOBNAME (smobnum);
+ kind = xstrprintf ("<%s>", name);
+ result = scm_from_latin1_symbol (kind);
+ xfree (kind);
+
+ return result;
+}
+
+/* (gsmob-property gsmob property) -> object
+ If property isn't present then #f is returned. */
+
+static SCM
+gdbscm_gsmob_property (SCM self, SCM property)
+{
+ SCM smob;
+ gdb_smob *base;
+
+ smob = gsscm_get_gsmob_arg_unsafe (self, SCM_ARG1, FUNC_NAME);
+ base = (gdb_smob *) SCM_SMOB_DATA (self);
+
+ /* Have we switched to a hash table? */
+ if (gdbscm_is_true (scm_hash_table_p (base->properties)))
+ return scm_hashq_ref (base->properties, property, SCM_BOOL_F);
+
+ return scm_assq_ref (base->properties, property);
+}
+
+/* (set-gsmob-property! gsmob property new-value) -> unspecified */
+
+static SCM
+gdbscm_set_gsmob_property_x (SCM self, SCM property, SCM new_value)
+{
+ SCM smob, alist;
+ gdb_smob *base;
+
+ smob = gsscm_get_gsmob_arg_unsafe (self, SCM_ARG1, FUNC_NAME);
+ base = (gdb_smob *) SCM_SMOB_DATA (self);
+
+ /* Have we switched to a hash table? */
+ if (gdbscm_is_true (scm_hash_table_p (base->properties)))
+ {
+ scm_hashq_set_x (base->properties, property, new_value);
+ return SCM_UNSPECIFIED;
+ }
+
+ alist = scm_assq_set_x (base->properties, property, new_value);
+
+ /* Did we grow the list? */
+ if (!scm_is_eq (alist, base->properties))
+ {
+ /* If we grew the list beyond a threshold in size,
+ switch to a hash table. */
+ if (scm_ilength (alist) >= SMOB_PROP_HTAB_THRESHOLD)
+ {
+ SCM elm, htab;
+
+ htab = scm_c_make_hash_table (SMOB_PROP_HTAB_THRESHOLD);
+ for (elm = alist; elm != SCM_EOL; elm = scm_cdr (elm))
+ scm_hashq_set_x (htab, scm_caar (elm), scm_cdar (elm));
+ base->properties = htab;
+ return SCM_UNSPECIFIED;
+ }
+ }
+
+ base->properties = alist;
+ return SCM_UNSPECIFIED;
+}
+
+/* (gsmob-has-property? gsmob property) -> boolean */
+
+static SCM
+gdbscm_gsmob_has_property_p (SCM self, SCM property)
+{
+ SCM smob, handle;
+ gdb_smob *base;
+
+ smob = gsscm_get_gsmob_arg_unsafe (self, SCM_ARG1, FUNC_NAME);
+ base = (gdb_smob *) SCM_SMOB_DATA (self);
+
+ if (gdbscm_is_true (scm_hash_table_p (base->properties)))
+ handle = scm_hashq_get_handle (base->properties, property);
+ else
+ handle = scm_assq (property, base->properties);
+
+ return scm_from_bool (gdbscm_is_true (handle));
+}
+
+/* Helper function for gdbscm_gsmob_properties. */
+
+static SCM
+add_property_name (void *closure, SCM handle)
+{
+ SCM *resultp = closure;
+
+ *resultp = scm_cons (scm_car (handle), *resultp);
+ return SCM_UNSPECIFIED;
+}
+
+/* (gsmob-properties gsmob) -> list
+ The list is unsorted. */
+
+static SCM
+gdbscm_gsmob_properties (SCM self)
+{
+ SCM smob, handle, result;
+ gdb_smob *base;
+
+ smob = gsscm_get_gsmob_arg_unsafe (self, SCM_ARG1, FUNC_NAME);
+ base = (gdb_smob *) SCM_SMOB_DATA (self);
+
+ result = SCM_EOL;
+ if (gdbscm_is_true (scm_hash_table_p (base->properties)))
+ {
+ scm_internal_hash_for_each_handle (add_property_name, &result,
+ base->properties);
+ }
+ else
+ {
+ SCM elm;
+
+ for (elm = base->properties; elm != SCM_EOL; elm = scm_cdr (elm))
+ result = scm_cons (scm_caar (elm), result);
+ }
+
+ return result;
+}
+
+/* When underlying gdb data structures are deleted, we need to update any
+ smobs with references to them. There are several smobs that reference
+ objfile-based data, so we provide helpers to manage this. */
+
+/* Add G_SMOB to the reference chain for OBJFILE specified by DATA_KEY.
+ OBJFILE may be NULL, in which case just set prev,next to NULL. */
+
+void
+gdbscm_add_objfile_ref (struct objfile *objfile,
+ const struct objfile_data *data_key,
+ chained_gdb_smob *g_smob)
+{
+ g_smob->prev = NULL;
+ if (objfile != NULL)
+ {
+ g_smob->next = objfile_data (objfile, data_key);
+ if (g_smob->next)
+ g_smob->next->prev = g_smob;
+ set_objfile_data (objfile, data_key, g_smob);
+ }
+ else
+ g_smob->next = NULL;
+}
+
+/* Remove G_SMOB from the reference chain for OBJFILE specified
+ by DATA_KEY. OBJFILE may be NULL. */
+
+void
+gdbscm_remove_objfile_ref (struct objfile *objfile,
+ const struct objfile_data *data_key,
+ chained_gdb_smob *g_smob)
+{
+ if (g_smob->prev)
+ g_smob->prev->next = g_smob->next;
+ else if (objfile != NULL)
+ set_objfile_data (objfile, data_key, g_smob->next);
+ if (g_smob->next)
+ g_smob->next->prev = g_smob->prev;
+}
+
+/* Create a hash table for mapping a pointer to a gdb data structure to the
+ gsmob that wraps it. */
+
+htab_t
+gdbscm_create_eqable_gsmob_ptr_map (htab_hash hash_fn, htab_eq eq_fn)
+{
+ htab_t htab = htab_create_alloc (7, hash_fn, eq_fn,
+ NULL, xcalloc, xfree);
+
+ return htab;
+}
+
+/* Return a pointer to the htab entry for the eq?-able gsmob BASE.
+ If the entry is found, *SLOT is non-NULL.
+ Otherwise *slot is NULL. */
+
+eqable_gdb_smob **
+gdbscm_find_eqable_gsmob_ptr_slot (htab_t htab, eqable_gdb_smob *base)
+{
+ void **slot = htab_find_slot (htab, base, INSERT);
+
+ return (eqable_gdb_smob **) slot;
+}
+
+/* Record CONTAINING_SCM as the object containing BASE, and record it in
+ SLOT. SLOT must be the result of calling gdbscm_find_eqable_gsmob_ptr_slot
+ on BASE (or equivalent for lookup). */
+
+void
+gdbscm_fill_eqable_gsmob_ptr_slot (eqable_gdb_smob **slot,
+ eqable_gdb_smob *base,
+ SCM containing_scm)
+{
+ base->containing_scm = containing_scm;
+ *slot = base;
+}
+
+/* Remove BASE from HTAB.
+ BASE is a pointer to a gsmob that wraps a pointer to a GDB datum.
+ This is used, for example, when an object is freed.
+
+ It is an error to call this if PTR is not in HTAB (only because it allows
+ for some consistency checking). */
+
+void
+gdbscm_clear_eqable_gsmob_ptr_slot (htab_t htab, eqable_gdb_smob *base)
+{
+ void **slot = htab_find_slot (htab, base, NO_INSERT);
+
+ gdb_assert (slot != NULL);
+ htab_clear_slot (htab, slot);
+}
+
+/* Initialize the Scheme gsmobs code. */
+
+static const scheme_function gsmob_functions[] =
+{
+ { "gsmob-kind", 1, 0, 0, gdbscm_gsmob_kind,
+ "\
+Return the kind of the smob, e.g., <gdb:breakpoint>, as a symbol." },
+
+ { "gsmob-property", 2, 0, 0, gdbscm_gsmob_property,
+ "\
+Return the specified property of the gsmob." },
+
+ { "set-gsmob-property!", 3, 0, 0, gdbscm_set_gsmob_property_x,
+ "\
+Set the specified property of the gsmob." },
+
+ { "gsmob-has-property?", 2, 0, 0, gdbscm_gsmob_has_property_p,
+ "\
+Return #t if the specified property is present." },
+
+ { "gsmob-properties", 1, 0, 0, gdbscm_gsmob_properties,
+ "\
+Return an unsorted list of names of properties." },
+
+ END_FUNCTIONS
+};
+
+void
+gdbscm_initialize_smobs (void)
+{
+ registered_gsmobs = htab_create_alloc (10,
+ hash_scm_t_bits, eq_scm_t_bits,
+ NULL, xcalloc, xfree);
+
+ gdbscm_define_functions (gsmob_functions, 1);
+}
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