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+/* unwind_prot.c - a simple unwind-protect system for internal variables */
+
+/* I can't stand it anymore! Please can't we just write the
+ whole Unix system in lisp or something? */
+
+/* Copyright (C) 1987-2021 Free Software Foundation, Inc.
+
+ This file is part of GNU Bash, the Bourne Again SHell.
+
+ Bash 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.
+
+ Bash 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 Bash. If not, see <http://www.gnu.org/licenses/>.
+*/
+
+/* **************************************************************** */
+/* */
+/* Unwind Protection Scheme for Bash */
+/* */
+/* **************************************************************** */
+#include "config.h"
+
+#include "bashtypes.h"
+#include "bashansi.h"
+
+#if defined (HAVE_UNISTD_H)
+# include <unistd.h>
+#endif
+
+#if defined (HAVE_STDDEF_H)
+# include <stddef.h>
+#endif
+
+#ifndef offsetof
+# define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
+#endif
+
+#include "command.h"
+#include "general.h"
+#include "unwind_prot.h"
+#include "sig.h"
+#include "quit.h"
+#include "bashintl.h" /* for _() */
+#include "error.h" /* for internal_warning */
+#include "ocache.h"
+
+/* Structure describing a saved variable and the value to restore it to. */
+typedef struct {
+ char *variable;
+ int size;
+ char desired_setting[1]; /* actual size is `size' */
+} SAVED_VAR;
+
+/* If HEAD.CLEANUP is null, then ARG.V contains a tag to throw back to.
+ If HEAD.CLEANUP is restore_variable, then SV.V contains the saved
+ variable. Otherwise, call HEAD.CLEANUP (ARG.V) to clean up. */
+typedef union uwp {
+ struct uwp_head {
+ union uwp *next;
+ Function *cleanup;
+ } head;
+ struct {
+ struct uwp_head uwp_head;
+ char *v;
+ } arg;
+ struct {
+ struct uwp_head uwp_head;
+ SAVED_VAR v;
+ } sv;
+} UNWIND_ELT;
+
+static void without_interrupts PARAMS((VFunction *, char *, char *));
+static void unwind_frame_discard_internal PARAMS((char *, char *));
+static void unwind_frame_run_internal PARAMS((char *, char *));
+static void add_unwind_protect_internal PARAMS((Function *, char *));
+static void remove_unwind_protect_internal PARAMS((char *, char *));
+static void run_unwind_protects_internal PARAMS((char *, char *));
+static void clear_unwind_protects_internal PARAMS((char *, char *));
+static inline void restore_variable PARAMS((SAVED_VAR *));
+static void unwind_protect_mem_internal PARAMS((char *, char *));
+
+static UNWIND_ELT *unwind_protect_list = (UNWIND_ELT *)NULL;
+
+/* Allocating from a cache of unwind-protect elements */
+#define UWCACHESIZE 128
+
+sh_obj_cache_t uwcache = {0, 0, 0};
+
+#if 0
+#define uwpalloc(elt) (elt) = (UNWIND_ELT *)xmalloc (sizeof (UNWIND_ELT))
+#define uwpfree(elt) free(elt)
+#else
+#define uwpalloc(elt) ocache_alloc (uwcache, UNWIND_ELT, elt)
+#define uwpfree(elt) ocache_free (uwcache, UNWIND_ELT, elt)
+#endif
+
+void
+uwp_init ()
+{
+ ocache_create (uwcache, UNWIND_ELT, UWCACHESIZE);
+}
+
+/* Run a function without interrupts. This relies on the fact that the
+ FUNCTION cannot call QUIT (). */
+static void
+without_interrupts (function, arg1, arg2)
+ VFunction *function;
+ char *arg1, *arg2;
+{
+ (*function)(arg1, arg2);
+}
+
+/* Start the beginning of a region. */
+void
+begin_unwind_frame (tag)
+ char *tag;
+{
+ add_unwind_protect ((Function *)NULL, tag);
+}
+
+/* Discard the unwind protects back to TAG. */
+void
+discard_unwind_frame (tag)
+ char *tag;
+{
+ if (unwind_protect_list)
+ without_interrupts (unwind_frame_discard_internal, tag, (char *)NULL);
+}
+
+/* Run the unwind protects back to TAG. */
+void
+run_unwind_frame (tag)
+ char *tag;
+{
+ if (unwind_protect_list)
+ without_interrupts (unwind_frame_run_internal, tag, (char *)NULL);
+}
+
+/* Add the function CLEANUP with ARG to the list of unwindable things. */
+void
+add_unwind_protect (cleanup, arg)
+ Function *cleanup;
+ char *arg;
+{
+ without_interrupts (add_unwind_protect_internal, (char *)cleanup, arg);
+}
+
+/* Remove the top unwind protect from the list. */
+void
+remove_unwind_protect ()
+{
+ if (unwind_protect_list)
+ without_interrupts
+ (remove_unwind_protect_internal, (char *)NULL, (char *)NULL);
+}
+
+/* Run the list of cleanup functions in unwind_protect_list. */
+void
+run_unwind_protects ()
+{
+ if (unwind_protect_list)
+ without_interrupts
+ (run_unwind_protects_internal, (char *)NULL, (char *)NULL);
+}
+
+/* Erase the unwind-protect list. If flags is 1, free the elements. */
+void
+clear_unwind_protect_list (flags)
+ int flags;
+{
+ char *flag;
+
+ if (unwind_protect_list)
+ {
+ flag = flags ? "" : (char *)NULL;
+ without_interrupts
+ (clear_unwind_protects_internal, flag, (char *)NULL);
+ }
+}
+
+int
+have_unwind_protects ()
+{
+ return (unwind_protect_list != 0);
+}
+
+int
+unwind_protect_tag_on_stack (tag)
+ const char *tag;
+{
+ UNWIND_ELT *elt;
+
+ elt = unwind_protect_list;
+ while (elt)
+ {
+ if (elt->head.cleanup == 0 && STREQ (elt->arg.v, tag))
+ return 1;
+ elt = elt->head.next;
+ }
+ return 0;
+}
+
+/* **************************************************************** */
+/* */
+/* The Actual Functions */
+/* */
+/* **************************************************************** */
+
+static void
+add_unwind_protect_internal (cleanup, arg)
+ Function *cleanup;
+ char *arg;
+{
+ UNWIND_ELT *elt;
+
+ uwpalloc (elt);
+ elt->head.next = unwind_protect_list;
+ elt->head.cleanup = cleanup;
+ elt->arg.v = arg;
+ unwind_protect_list = elt;
+}
+
+static void
+remove_unwind_protect_internal (ignore1, ignore2)
+ char *ignore1, *ignore2;
+{
+ UNWIND_ELT *elt;
+
+ elt = unwind_protect_list;
+ if (elt)
+ {
+ unwind_protect_list = unwind_protect_list->head.next;
+ uwpfree (elt);
+ }
+}
+
+static void
+run_unwind_protects_internal (ignore1, ignore2)
+ char *ignore1, *ignore2;
+{
+ unwind_frame_run_internal ((char *) NULL, (char *) NULL);
+}
+
+static void
+clear_unwind_protects_internal (flag, ignore)
+ char *flag, *ignore;
+{
+ if (flag)
+ {
+ while (unwind_protect_list)
+ remove_unwind_protect_internal ((char *)NULL, (char *)NULL);
+ }
+ unwind_protect_list = (UNWIND_ELT *)NULL;
+}
+
+static void
+unwind_frame_discard_internal (tag, ignore)
+ char *tag, *ignore;
+{
+ UNWIND_ELT *elt;
+ int found;
+
+ found = 0;
+ while (elt = unwind_protect_list)
+ {
+ unwind_protect_list = unwind_protect_list->head.next;
+ if (elt->head.cleanup == 0 && (STREQ (elt->arg.v, tag)))
+ {
+ uwpfree (elt);
+ found = 1;
+ break;
+ }
+ else
+ uwpfree (elt);
+ }
+
+ if (found == 0)
+ internal_warning (_("unwind_frame_discard: %s: frame not found"), tag);
+}
+
+/* Restore the value of a variable, based on the contents of SV.
+ sv->desired_setting is a block of memory SIZE bytes long holding the
+ value itself. This block of memory is copied back into the variable. */
+static inline void
+restore_variable (sv)
+ SAVED_VAR *sv;
+{
+ FASTCOPY (sv->desired_setting, sv->variable, sv->size);
+}
+
+static void
+unwind_frame_run_internal (tag, ignore)
+ char *tag, *ignore;
+{
+ UNWIND_ELT *elt;
+ int found;
+
+ found = 0;
+ while (elt = unwind_protect_list)
+ {
+ unwind_protect_list = elt->head.next;
+
+ /* If tag, then compare. */
+ if (elt->head.cleanup == 0)
+ {
+ if (tag && STREQ (elt->arg.v, tag))
+ {
+ uwpfree (elt);
+ found = 1;
+ break;
+ }
+ }
+ else
+ {
+ if (elt->head.cleanup == (Function *) restore_variable)
+ restore_variable (&elt->sv.v);
+ else
+ (*(elt->head.cleanup)) (elt->arg.v);
+ }
+
+ uwpfree (elt);
+ }
+ if (tag && found == 0)
+ internal_warning (_("unwind_frame_run: %s: frame not found"), tag);
+}
+
+static void
+unwind_protect_mem_internal (var, psize)
+ char *var;
+ char *psize;
+{
+ int size, allocated;
+ UNWIND_ELT *elt;
+
+ size = *(int *) psize;
+ allocated = size + offsetof (UNWIND_ELT, sv.v.desired_setting[0]);
+ if (allocated < sizeof (UNWIND_ELT))
+ allocated = sizeof (UNWIND_ELT);
+ elt = (UNWIND_ELT *)xmalloc (allocated);
+ elt->head.next = unwind_protect_list;
+ elt->head.cleanup = (Function *) restore_variable;
+ elt->sv.v.variable = var;
+ elt->sv.v.size = size;
+ FASTCOPY (var, elt->sv.v.desired_setting, size);
+ unwind_protect_list = elt;
+}
+
+/* Save the value of a variable so it will be restored when unwind-protects
+ are run. VAR is a pointer to the variable. SIZE is the size in
+ bytes of VAR. */
+void
+unwind_protect_mem (var, size)
+ char *var;
+ int size;
+{
+ without_interrupts (unwind_protect_mem_internal, var, (char *) &size);
+}
+
+#if defined (DEBUG)
+#include <stdio.h>
+
+void
+print_unwind_protect_tags ()
+{
+ UNWIND_ELT *elt;
+
+ elt = unwind_protect_list;
+ while (elt)
+ {
+ if (elt->head.cleanup == 0)
+ fprintf(stderr, "tag: %s\n", elt->arg.v);
+ elt = elt->head.next;
+ }
+}
+#endif
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