+#include "gdb_assert.h"
+
+/* The cleanup list records things that have to be undone
+ if an error happens (descriptors to be closed, memory to be freed, etc.)
+ Each link in the chain records a function to call and an
+ argument to give it.
+
+ Use make_cleanup to add an element to the cleanup chain.
+ Use do_cleanups to do all cleanup actions back to a given
+ point in the chain. Use discard_cleanups to remove cleanups
+ from the chain back to a given point, not doing them.
+
+ If the argument is pointer to allocated memory, then you need
+ to additionally set the 'free_arg' member to a function that will
+ free that memory. This function will be called both when the cleanup
+ is executed and when it's discarded. */
+
+struct cleanup
+{
+ struct cleanup *next;
+ void (*function) (void *);
+ void (*free_arg) (void *);
+ void *arg;
+};
+
+/* Used to mark the end of a cleanup chain.
+ The value is chosen so that it:
+ - is non-NULL so that make_cleanup never returns NULL,
+ - causes a segv if dereferenced
+ [though this won't catch errors that a value of, say,
+ ((struct cleanup *) -1) will]
+ - displays as something useful when printed in gdb.
+ This is const for a bit of extra robustness.
+ It is initialized to coax gcc into putting it into .rodata.
+ All fields are initialized to survive -Wextra. */
+static const struct cleanup sentinel_cleanup = { 0, 0, 0, 0 };
+
+/* Handy macro to use when referring to sentinel_cleanup. */
+#define SENTINEL_CLEANUP ((struct cleanup *) &sentinel_cleanup)