talloc_free().
If you find this confusing, then I suggest you run the LOCAL-TALLOC
-smbtorture test with the --leak-report-full option to watch talloc in
-action. You may also like to add your own tests to
-source/torture/local/talloc.c to clarify how some particular situation
-is handled.
+smbtorture test to watch talloc in action. You may also like to add
+your own tests to source/torture/local/talloc.c to clarify how some
+particular situation is handled.
+
+
+Performance
+-----------
+
+All the additional features of talloc() over malloc() do come at a
+price. We have a simple performance test in Samba4 that measures
+talloc() versus malloc() performance, and it seems that talloc() is
+about 10% slower than malloc() on my x86 Debian Linux box. For Samba,
+the great reduction in code complexity that we get by using talloc
+makes this worthwhile, especially as the total overhead of
+talloc/malloc in Samba is already quite small.
talloc API
level context is created.
+=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+void *talloc_p(const void *context, type);
+
+The talloc_p() macro is the equivalent of
+
+ (type *)talloc(ctx, sizeof(type))
+
+You should use it in preference to talloc() whenever possible, as it
+provides additional type safety. It also automatically calls the
+talloc_set_name_const() function with the name being a string holding
+the name of the type.
+
+
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
int talloc_free(void *ptr);
destructor returned -1. See talloc_set_destructor() for details on
destructors.
-If this pointer has an additional reference when talloc_free() is
-called then the memory is not actually released, but instead the
-reference is destroyed and the memory becomes a child of the
-referrer. See talloc_reference() for details on establishing
-additional references.
+If this pointer has an additional parent when talloc_free() is called
+then the memory is not actually released, but instead the most
+recently established parent is destroyed. See talloc_reference() for
+details on establishing additional parents.
+
+For more control on which parent is removed, see talloc_unlink()
talloc_free() operates recursively on its children.
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
void *talloc_reference(const void *context, const void *ptr);
-The talloc_reference() function returns an additional reference to
-"ptr", and makes this additional reference a child of "context".
+The talloc_reference() function makes "context" an additional parent
+of "ptr".
The return value of talloc_reference() is always the original pointer
"ptr", unless talloc ran out of memory in creating the reference in
which case it will return NULL (each additional reference consumes
around 48 bytes of memory on intel x86 platforms).
+If "ptr" is NULL, then the function is a no-op, and simply returns NULL.
+
After creating a reference you can free it in one of the following
ways:
- - you can talloc_free() a parent of the original pointer. That will
- destroy the reference and make the pointer a child of "context".
+ - you can talloc_free() any parent of the original pointer. That
+ will reduce the number of parents of this pointer by 1, and will
+ cause this pointer to be freed if it runs out of parents.
- you can talloc_free() the pointer itself. That will destroy the
- reference and make the pointer a child of "context".
+ most recently established parent to the pointer and leave the
+ pointer as a child of its current parent.
- - you can talloc_free() the context where you placed the
- reference. That will destroy the reference, and leave the pointer
- where it is.
+For more control on which parent to remove, see talloc_unlink()
+
+
+=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+int talloc_unlink(const void *context, const void *ptr);
+
+The talloc_unlink() function removes a specific parent from ptr. The
+context passed must either be a context used in talloc_reference()
+with this pointer, or must be a direct parent of ptr.
+
+Note that if the parent has already been removed using talloc_free()
+then this function will fail and will return -1. Likewise, if "ptr"
+is NULL, then the function will make no modifications and return -1.
+
+Usually you can just use talloc_free() instead of talloc_unlink(), but
+sometimes it is useful to have the additional control on which parent
+is removed.
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
talloc_report() and talloc_report_full() for details. Also see
talloc_enable_leak_report() and talloc_enable_leak_report_full().
+The talloc_set_name() function allocates memory as a child of the
+pointer. It is logically equivalent to:
+ talloc_set_name_const(ptr, talloc_asprintf(ptr, fmt, ...));
+
+Note that multiple calls to talloc_set_name() will allocate more
+memory without releasing the name. All of the memory is released when
+the ptr is freed using talloc_free().
+
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
void talloc_set_name_const(const void *ptr, const char *name);
but it takes a string constant, and is much faster. It is extensively
used by the "auto naming" macros, such as talloc_p().
+This function does not allocate any memory. It just copies the
+supplied pointer into the internal representation of the talloc
+ptr. This means you must not pass a name pointer to memory that will
+disappear before the ptr is freed with talloc_free().
+
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
void *talloc_named(const void *context, size_t size, const char *fmt, ...);
talloc_realloc() returns the new pointer, or NULL on failure. The call
will fail either due to a lack of memory, or because the pointer has
-an reference (see talloc_reference()).
+more than one parent (see talloc_reference()).
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
The talloc_total_size() function returns the total size in bytes used
by this pointer and all child pointers. Mostly useful for debugging.
+Passing NULL is allowed, but it will only give a meaningful result if
+talloc_enable_leak_report() or talloc_enable_leak_report_full() has
+been called.
+
+
+=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+off_t talloc_total_blocks(const void *ptr);
+
+The talloc_total_blocks() function returns the total memory block
+count used by this pointer and all child pointers. Mostly useful for
+debugging.
+
+Passing NULL is allowed, but it will only give a meaningful result if
+talloc_enable_leak_report() or talloc_enable_leak_report_full() has
+been called.
+
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
void talloc_report(const void *ptr, FILE *f);
ptr, showing the total memory and number of blocks used by that child.
You can pass NULL for the pointer, in which case a report is printed
-for the top level memory context.
+for the top level memory context, but only if
+talloc_enable_leak_report() or talloc_enable_leak_report_full() has
+been called.
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
pointer that is referenced.
You can pass NULL for the pointer, in which case a report is printed
-for the top level memory context.
+for the top level memory context, but only if
+talloc_enable_leak_report() or talloc_enable_leak_report_full() has
+been called.
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
exits. In Samba4 this is enabled by using the --leak-report command
line option.
+For it to be useful, this function must be called before any other
+talloc function as it establishes a "null context" that acts as the
+top of the tree. If you don't call this function first then passing
+NULL to talloc_report() or talloc_report_full() won't give you the
+full tree printout.
+
+Here is a typical talloc report:
+
+talloc report on 'null_context' (total 267 bytes in 15 blocks)
+ libcli/auth/spnego_parse.c:55 contains 31 bytes in 2 blocks
+ libcli/auth/spnego_parse.c:55 contains 31 bytes in 2 blocks
+ iconv(UTF8,CP850) contains 42 bytes in 2 blocks
+ libcli/auth/spnego_parse.c:55 contains 31 bytes in 2 blocks
+ iconv(CP850,UTF8) contains 42 bytes in 2 blocks
+ iconv(UTF8,UTF-16LE) contains 45 bytes in 2 blocks
+ iconv(UTF-16LE,UTF8) contains 45 bytes in 2 blocks
+
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
void talloc_enable_leak_report_full(void);
program exits. In Samba4 this is enabled by using the
--leak-report-full command line option.
+For it to be useful, this function must be called before any other
+talloc function as it establishes a "null context" that acts as the
+top of the tree. If you don't call this function first then passing
+NULL to talloc_report() or talloc_report_full() won't give you the
+full tree printout.
+
+Here is a typical full report:
+
+full talloc report on 'root' (total 18 bytes in 8 blocks)
+ p1 contains 18 bytes in 7 blocks (ref 0)
+ r1 contains 13 bytes in 2 blocks (ref 0)
+ reference to: p2
+ p2 contains 1 bytes in 1 blocks (ref 1)
+ x3 contains 1 bytes in 1 blocks (ref 0)
+ x2 contains 1 bytes in 1 blocks (ref 0)
+ x1 contains 1 bytes in 1 blocks (ref 0)
+
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
void *talloc_zero(const void *ctx, size_t size);
ptr = talloc(ctx, strlen(p)+1);
if (ptr) memcpy(ptr, p, strlen(p)+1);
+This functions sets the name of the new pointer to the passed
+string. This is equivalent to:
+ talloc_set_name_const(ptr, ptr)
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
char *talloc_strndup(const void *t, const char *p, size_t n);
The talloc_strndup() function is the talloc equivalent of the C
library function strndup()
+This functions sets the name of the new pointer to the passed
+string. This is equivalent to:
+ talloc_set_name_const(ptr, ptr)
+
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
char *talloc_vasprintf(const void *t, const char *fmt, va_list ap);
The talloc_asprintf() function is the talloc equivalent of the C
library function asprintf()
+This functions sets the name of the new pointer to the passed
+string. This is equivalent to:
+ talloc_set_name_const(ptr, ptr)
+
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
char *talloc_asprintf_append(char *s, const char *fmt, ...);
except that it provides integer overflow protection for the multiply,
returning NULL if the multiply overflows.
+
+=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+void *talloc_realloc_fn(const void *ctx, void *ptr, size_t size);
+
+This is a non-macro version of talloc_realloc(), which is useful
+as libraries sometimes want a ralloc function pointer. A realloc()
+implementation encapsulates the functionality of malloc(), free() and
+realloc() in one call, which is why it is useful to be able to pass
+around a single function pointer.
+
git.samba.org / samba.git / blobdiff