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diff --git a/lib/talloc/talloc.3.xml b/lib/talloc/talloc.3.xml new file mode 100644 index 0000000000..67de15bfc8 --- /dev/null +++ b/lib/talloc/talloc.3.xml @@ -0,0 +1,738 @@ +<?xml version="1.0"?> +<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> +<refentry> + <refmeta> + <refentrytitle>talloc</refentrytitle> + <manvolnum>3</manvolnum> + </refmeta> + <refnamediv> + <refname>talloc</refname> +<refpurpose>hierarchical reference counted memory pool system with destructors</refpurpose> + </refnamediv> + <refsynopsisdiv> +<synopsis>#include <talloc/talloc.h></synopsis> + </refsynopsisdiv> + <refsect1><title>DESCRIPTION</title> + <para> + If you are used to talloc from Samba3 then please read this + carefully, as talloc has changed a lot. + </para> + <para> + The new talloc is a hierarchical, reference counted memory pool + system with destructors. Quite a mouthful really, but not too bad + once you get used to it. + </para> + <para> + Perhaps the biggest change from Samba3 is that there is no + distinction between a "talloc context" and a "talloc pointer". Any + pointer returned from talloc() is itself a valid talloc context. + This means you can do this: + </para> + <programlisting> + struct foo *X = talloc(mem_ctx, struct foo); + X->name = talloc_strdup(X, "foo"); + </programlisting> + <para> + and the pointer <literal role="code">X->name</literal> + would be a "child" of the talloc context <literal + role="code">X</literal> which is itself a child of + <literal role="code">mem_ctx</literal>. So if you do + <literal role="code">talloc_free(mem_ctx)</literal> then + it is all destroyed, whereas if you do <literal + role="code">talloc_free(X)</literal> then just <literal + role="code">X</literal> and <literal + role="code">X->name</literal> are destroyed, and if + you do <literal + role="code">talloc_free(X->name)</literal> then just + the name element of <literal role="code">X</literal> is + destroyed. + </para> + <para> + If you think about this, then what this effectively gives you is an + n-ary tree, where you can free any part of the tree with + talloc_free(). + </para> + <para> + If you find this confusing, then I suggest you run the <literal + role="code">testsuite</literal> program to watch talloc + in action. You may also like to add your own tests to <literal + role="code">testsuite.c</literal> to clarify how some + particular situation is handled. + </para> + </refsect1> + <refsect1><title>TALLOC API</title> + <para> + The following is a complete guide to the talloc API. Read it all at + least twice. + </para> + <refsect2><title>(type *)talloc(const void *ctx, type);</title> + <para> + The talloc() macro is the core of the talloc library. It takes a + memory <emphasis role="italic">ctx</emphasis> and a <emphasis + role="italic">type</emphasis>, and returns a pointer to a new + area of memory of the given <emphasis + role="italic">type</emphasis>. + </para> + <para> + The returned pointer is itself a talloc context, so you can use + it as the <emphasis role="italic">ctx</emphasis> argument to more + calls to talloc() if you wish. + </para> + <para> + The returned pointer is a "child" of the supplied context. This + means that if you talloc_free() the <emphasis + role="italic">ctx</emphasis> then the new child disappears as + well. Alternatively you can free just the child. + </para> + <para> + The <emphasis role="italic">ctx</emphasis> argument to talloc() + can be NULL, in which case a new top level context is created. + </para> + </refsect2> + <refsect2><title>void *talloc_size(const void *ctx, size_t size);</title> + <para> + The function talloc_size() should be used when you don't have a + convenient type to pass to talloc(). Unlike talloc(), it is not + type safe (as it returns a void *), so you are on your own for + type checking. + </para> + </refsect2> + <refsect2><title>(typeof(ptr)) talloc_ptrtype(const void *ctx, ptr);</title> + <para> + The talloc_ptrtype() macro should be used when you have a pointer and + want to allocate memory to point at with this pointer. When compiling + with gcc >= 3 it is typesafe. Note this is a wrapper of talloc_size() + and talloc_get_name() will return the current location in the source file. + and not the type. + </para> + </refsect2> + <refsect2><title>int talloc_free(void *ptr);</title> + <para> + The talloc_free() function frees a piece of talloc memory, and + all its children. You can call talloc_free() on any pointer + returned by talloc(). + </para> + <para> + The return value of talloc_free() indicates success or failure, + with 0 returned for success and -1 for failure. The only + possible failure condition is if <emphasis + role="italic">ptr</emphasis> had a destructor attached to it and + the destructor returned -1. See <link + linkend="talloc_set_destructor"><quote>talloc_set_destructor()</quote></link> + for details on destructors. + </para> + <para> + 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 <link + linkend="talloc_reference"><quote>talloc_reference()</quote></link> + for details on establishing additional parents. + </para> + <para> + For more control on which parent is removed, see <link + linkend="talloc_unlink"><quote>talloc_unlink()</quote></link>. + </para> + <para> + talloc_free() operates recursively on its children. + </para> + </refsect2> + <refsect2 id="talloc_reference"><title>void *talloc_reference(const void *ctx, const void *ptr);</title> + <para> + The talloc_reference() function makes <emphasis + role="italic">ctx</emphasis> an additional parent of <emphasis + role="italic">ptr</emphasis>. + </para> + <para> + The return value of talloc_reference() is always the original + pointer <emphasis role="italic">ptr</emphasis>, 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). + </para> + <para> + If <emphasis role="italic">ptr</emphasis> is NULL, then the + function is a no-op, and simply returns NULL. + </para> + <para> + After creating a reference you can free it in one of the + following ways: + </para> + <para> + <itemizedlist> + <listitem> + <para> + 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. + </para> + </listitem> + <listitem> + <para> + you can talloc_free() the pointer itself. That will destroy + the most recently established parent to the pointer and leave + the pointer as a child of its current parent. + </para> + </listitem> + </itemizedlist> + </para> + <para> + For more control on which parent to remove, see <link + linkend="talloc_unlink"><quote>talloc_unlink()</quote></link>. + </para> + </refsect2> + <refsect2 id="talloc_unlink"><title>int talloc_unlink(const void *ctx, const void *ptr);</title> + <para> + The talloc_unlink() function removes a specific parent from + <emphasis role="italic">ptr</emphasis>. The <emphasis + role="italic">ctx</emphasis> passed must either be a context used + in talloc_reference() with this pointer, or must be a direct + parent of ptr. + </para> + <para> + Note that if the parent has already been removed using + talloc_free() then this function will fail and will return -1. + Likewise, if <emphasis role="italic">ptr</emphasis> is NULL, then + the function will make no modifications and return -1. + </para> + <para> + 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. + </para> + </refsect2> + <refsect2 id="talloc_set_destructor"><title>void talloc_set_destructor(const void *ptr, int (*destructor)(void *));</title> + <para> + The function talloc_set_destructor() sets the <emphasis + role="italic">destructor</emphasis> for the pointer <emphasis + role="italic">ptr</emphasis>. A <emphasis + role="italic">destructor</emphasis> is a function that is called + when the memory used by a pointer is about to be released. The + destructor receives <emphasis role="italic">ptr</emphasis> as an + argument, and should return 0 for success and -1 for failure. + </para> + <para> + The <emphasis role="italic">destructor</emphasis> can do anything + it wants to, including freeing other pieces of memory. A common + use for destructors is to clean up operating system resources + (such as open file descriptors) contained in the structure the + destructor is placed on. + </para> + <para> + You can only place one destructor on a pointer. If you need more + than one destructor then you can create a zero-length child of + the pointer and place an additional destructor on that. + </para> + <para> + To remove a destructor call talloc_set_destructor() with NULL for + the destructor. + </para> + <para> + If your destructor attempts to talloc_free() the pointer that it + is the destructor for then talloc_free() will return -1 and the + free will be ignored. This would be a pointless operation + anyway, as the destructor is only called when the memory is just + about to go away. + </para> + </refsect2> + <refsect2><title>int talloc_increase_ref_count(const void *<emphasis role="italic">ptr</emphasis>);</title> + <para> + The talloc_increase_ref_count(<emphasis + role="italic">ptr</emphasis>) function is exactly equivalent to: + </para> + <programlisting>talloc_reference(NULL, ptr);</programlisting> + <para> + You can use either syntax, depending on which you think is + clearer in your code. + </para> + <para> + It returns 0 on success and -1 on failure. + </para> + </refsect2> + <refsect2><title>size_t talloc_reference_count(const void *<emphasis role="italic">ptr</emphasis>);</title> + <para> + Return the number of references to the pointer. + </para> + </refsect2> + <refsect2 id="talloc_set_name"><title>void talloc_set_name(const void *ptr, const char *fmt, ...);</title> + <para> + Each talloc pointer has a "name". The name is used principally + for debugging purposes, although it is also possible to set and + get the name on a pointer in as a way of "marking" pointers in + your code. + </para> + <para> + The main use for names on pointer is for "talloc reports". See + <link + linkend="talloc_report"><quote>talloc_report_depth_cb()</quote></link>, + <link + linkend="talloc_report"><quote>talloc_report_depth_file()</quote></link>, + <link + linkend="talloc_report"><quote>talloc_report()</quote></link> + <link + linkend="talloc_report"><quote>talloc_report()</quote></link> + and <link + linkend="talloc_report_full"><quote>talloc_report_full()</quote></link> + for details. Also see <link + linkend="talloc_enable_leak_report"><quote>talloc_enable_leak_report()</quote></link> + and <link + linkend="talloc_enable_leak_report_full"><quote>talloc_enable_leak_report_full()</quote></link>. + </para> + <para> + The talloc_set_name() function allocates memory as a child of the + pointer. It is logically equivalent to: + </para> + <programlisting>talloc_set_name_const(ptr, talloc_asprintf(ptr, fmt, ...));</programlisting> + <para> + 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(). + </para> + </refsect2> + <refsect2><title>void talloc_set_name_const(const void *<emphasis role="italic">ptr</emphasis>, const char *<emphasis role="italic">name</emphasis>);</title> + <para> + The function talloc_set_name_const() is just like + talloc_set_name(), but it takes a string constant, and is much + faster. It is extensively used by the "auto naming" macros, such + as talloc_p(). + </para> + <para> + 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 <emphasis + role="italic">name</emphasis> pointer to memory that will + disappear before <emphasis role="italic">ptr</emphasis> is freed + with talloc_free(). + </para> + </refsect2> + <refsect2><title>void *talloc_named(const void *<emphasis role="italic">ctx</emphasis>, size_t <emphasis role="italic">size</emphasis>, const char *<emphasis role="italic">fmt</emphasis>, ...);</title> + <para> + The talloc_named() function creates a named talloc pointer. It + is equivalent to: + </para> + <programlisting>ptr = talloc_size(ctx, size); +talloc_set_name(ptr, fmt, ....);</programlisting> + </refsect2> + <refsect2><title>void *talloc_named_const(const void *<emphasis role="italic">ctx</emphasis>, size_t <emphasis role="italic">size</emphasis>, const char *<emphasis role="italic">name</emphasis>);</title> + <para> + This is equivalent to: + </para> + <programlisting>ptr = talloc_size(ctx, size); +talloc_set_name_const(ptr, name);</programlisting> + </refsect2> + <refsect2><title>const char *talloc_get_name(const void *<emphasis role="italic">ptr</emphasis>);</title> + <para> + This returns the current name for the given talloc pointer, + <emphasis role="italic">ptr</emphasis>. See <link + linkend="talloc_set_name"><quote>talloc_set_name()</quote></link> + for details. + </para> + </refsect2> + <refsect2><title>void *talloc_init(const char *<emphasis role="italic">fmt</emphasis>, ...);</title> + <para> + This function creates a zero length named talloc context as a top + level context. It is equivalent to: + </para> + <programlisting>talloc_named(NULL, 0, fmt, ...);</programlisting> + </refsect2> + <refsect2><title>void *talloc_new(void *<emphasis role="italic">ctx</emphasis>);</title> + <para> + This is a utility macro that creates a new memory context hanging + off an exiting context, automatically naming it "talloc_new: + __location__" where __location__ is the source line it is called + from. It is particularly useful for creating a new temporary + working context. + </para> + </refsect2> + <refsect2><title>(<emphasis role="italic">type</emphasis> *)talloc_realloc(const void *<emphasis role="italic">ctx</emphasis>, void *<emphasis role="italic">ptr</emphasis>, <emphasis role="italic">type</emphasis>, <emphasis role="italic">count</emphasis>);</title> + <para> + The talloc_realloc() macro changes the size of a talloc pointer. + It has the following equivalences: + </para> + <programlisting>talloc_realloc(ctx, NULL, type, 1) ==> talloc(ctx, type); +talloc_realloc(ctx, ptr, type, 0) ==> talloc_free(ptr);</programlisting> + <para> + The <emphasis role="italic">ctx</emphasis> argument is only used + if <emphasis role="italic">ptr</emphasis> is not NULL, otherwise + it is ignored. + </para> + <para> + 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 more than one parent (see <link + linkend="talloc_reference"><quote>talloc_reference()</quote></link>). + </para> + </refsect2> + <refsect2><title>void *talloc_realloc_size(const void *ctx, void *ptr, size_t size);</title> + <para> + the talloc_realloc_size() function is useful when the type is not + known so the type-safe talloc_realloc() cannot be used. + </para> + </refsect2> + <refsect2><title>TYPE *talloc_steal(const void *<emphasis role="italic">new_ctx</emphasis>, const TYPE *<emphasis role="italic">ptr</emphasis>);</title> + <para> + The talloc_steal() function changes the parent context of a + talloc pointer. It is typically used when the context that the + pointer is currently a child of is going to be freed and you wish + to keep the memory for a longer time. + </para> + <para> + The talloc_steal() function returns the pointer that you pass it. + It does not have any failure modes. + </para> + <para> + NOTE: It is possible to produce loops in the parent/child + relationship if you are not careful with talloc_steal(). No + guarantees are provided as to your sanity or the safety of your + data if you do this. + </para> + </refsect2> + <refsect2><title>TYPE *talloc_move(const void *<emphasis role="italic">new_ctx</emphasis>, TYPE **<emphasis role="italic">ptr</emphasis>);</title> + <para> + The talloc_move() function is a wrapper around + talloc_steal() which zeros the source pointer after the + move. This avoids a potential source of bugs where a + programmer leaves a pointer in two structures, and uses the + pointer from the old structure after it has been moved to a + new one. + </para> + </refsect2> + <refsect2><title>size_t talloc_total_size(const void *<emphasis role="italic">ptr</emphasis>);</title> + <para> + The talloc_total_size() function returns the total size in bytes + used by this pointer and all child pointers. Mostly useful for + debugging. + </para> + <para> + 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. + </para> + </refsect2> + <refsect2><title>size_t talloc_total_blocks(const void *<emphasis role="italic">ptr</emphasis>);</title> + <para> + The talloc_total_blocks() function returns the total memory block + count used by this pointer and all child pointers. Mostly useful + for debugging. + </para> + <para> + 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. + </para> + </refsect2> + <refsect2 id="talloc_report"><title>void talloc_report(const void *ptr, FILE *f);</title> + <para> + The talloc_report() function prints a summary report of all + memory used by <emphasis role="italic">ptr</emphasis>. One line + of report is printed for each immediate child of ptr, showing the + total memory and number of blocks used by that child. + </para> + <para> + You can pass NULL for the pointer, in which case a report is + printed for the top level memory context, but only if + talloc_enable_leak_report() or talloc_enable_leak_report_full() + has been called. + </para> + </refsect2> + <refsect2 id="talloc_report_full"><title>void talloc_report_full(const void *<emphasis role="italic">ptr</emphasis>, FILE *<emphasis role="italic">f</emphasis>);</title> + <para> + This provides a more detailed report than talloc_report(). It + will recursively print the entire tree of memory referenced by + the pointer. References in the tree are shown by giving the name + of the pointer that is referenced. + </para> + <para> + You can pass NULL for the pointer, in which case a report is + printed for the top level memory context, but only if + talloc_enable_leak_report() or talloc_enable_leak_report_full() + has been called. + </para> + </refsect2> + <refsect2 id="talloc_report_depth_cb"> + <funcsynopsis><funcprototype> + <funcdef>void <function>talloc_report_depth_cb</function></funcdef> + <paramdef><parameter>const void *ptr</parameter></paramdef> + <paramdef><parameter>int depth</parameter></paramdef> + <paramdef><parameter>int max_depth</parameter></paramdef> + <paramdef><parameter>void (*callback)(const void *ptr, int depth, int max_depth, int is_ref, void *priv)</parameter></paramdef> + <paramdef><parameter>void *priv</parameter></paramdef> + </funcprototype></funcsynopsis> + <para> + This provides a more flexible reports than talloc_report(). It + will recursively call the callback for the entire tree of memory + referenced by the pointer. References in the tree are passed with + <emphasis role="italic">is_ref = 1</emphasis> and the pointer that is referenced. + </para> + <para> + You can pass NULL for the pointer, in which case a report is + printed for the top level memory context, but only if + talloc_enable_leak_report() or talloc_enable_leak_report_full() + has been called. + </para> + <para> + The recursion is stopped when depth >= max_depth. + max_depth = -1 means only stop at leaf nodes. + </para> + </refsect2> + <refsect2 id="talloc_report_depth_file"> + <funcsynopsis><funcprototype> + <funcdef>void <function>talloc_report_depth_file</function></funcdef> + <paramdef><parameter>const void *ptr</parameter></paramdef> + <paramdef><parameter>int depth</parameter></paramdef> + <paramdef><parameter>int max_depth</parameter></paramdef> + <paramdef><parameter>FILE *f</parameter></paramdef> + </funcprototype></funcsynopsis> + <para> + This provides a more flexible reports than talloc_report(). It + will let you specify the depth and max_depth. + </para> + </refsect2> + <refsect2 id="talloc_enable_leak_report"><title>void talloc_enable_leak_report(void);</title> + <para> + This enables calling of talloc_report(NULL, stderr) when the + program exits. In Samba4 this is enabled by using the + --leak-report command line option. + </para> + <para> + 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. + </para> + <para> + Here is a typical talloc report: + </para> + <screen format="linespecific">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 + </screen> + </refsect2> + <refsect2 id="talloc_enable_leak_report_full"><title>void talloc_enable_leak_report_full(void);</title> + <para> + This enables calling of talloc_report_full(NULL, stderr) when the + program exits. In Samba4 this is enabled by using the + --leak-report-full command line option. + </para> + <para> + 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. + </para> + <para> + Here is a typical full report: + </para> + <screen format="linespecific">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) + </screen> + </refsect2> + <refsect2><title>(<emphasis role="italic">type</emphasis> *)talloc_zero(const void *<emphasis role="italic">ctx</emphasis>, <emphasis role="italic">type</emphasis>);</title> + <para> + The talloc_zero() macro is equivalent to: + </para> + <programlisting>ptr = talloc(ctx, type); +if (ptr) memset(ptr, 0, sizeof(type));</programlisting> + </refsect2> + <refsect2><title>void *talloc_zero_size(const void *<emphasis role="italic">ctx</emphasis>, size_t <emphasis role="italic">size</emphasis>)</title> + <para> + The talloc_zero_size() function is useful when you don't have a + known type. + </para> + </refsect2> + <refsect2><title>void *talloc_memdup(const void *<emphasis role="italic">ctx</emphasis>, const void *<emphasis role="italic">p</emphasis>, size_t size);</title> + <para> + The talloc_memdup() function is equivalent to: + </para> + <programlisting>ptr = talloc_size(ctx, size); +if (ptr) memcpy(ptr, p, size);</programlisting> + </refsect2> + <refsect2><title>char *talloc_strdup(const void *<emphasis role="italic">ctx</emphasis>, const char *<emphasis role="italic">p</emphasis>);</title> + <para> + The talloc_strdup() function is equivalent to: + </para> + <programlisting>ptr = talloc_size(ctx, strlen(p)+1); +if (ptr) memcpy(ptr, p, strlen(p)+1);</programlisting> + <para> + This function sets the name of the new pointer to the passed + string. This is equivalent to: + </para> + <programlisting>talloc_set_name_const(ptr, ptr)</programlisting> + </refsect2> + <refsect2><title>char *talloc_strndup(const void *<emphasis role="italic">t</emphasis>, const char *<emphasis role="italic">p</emphasis>, size_t <emphasis role="italic">n</emphasis>);</title> + <para> + The talloc_strndup() function is the talloc equivalent of the C + library function strndup(3). + </para> + <para> + This function sets the name of the new pointer to the passed + string. This is equivalent to: + </para> + <programlisting>talloc_set_name_const(ptr, ptr)</programlisting> + </refsect2> + <refsect2><title>char *talloc_append_string(const void *<emphasis role="italic">t</emphasis>, char *<emphasis role="italic">orig</emphasis>, const char *<emphasis role="italic">append</emphasis>);</title> + <para> + The talloc_append_string() function appends the given formatted + string to the given string. + </para> + <para> + This function sets the name of the new pointer to the new + string. This is equivalent to: + </para> + <programlisting>talloc_set_name_const(ptr, ptr)</programlisting> + </refsect2> + <refsect2><title>char *talloc_vasprintf(const void *<emphasis role="italic">t</emphasis>, const char *<emphasis role="italic">fmt</emphasis>, va_list <emphasis role="italic">ap</emphasis>);</title> + <para> + The talloc_vasprintf() function is the talloc equivalent of the C + library function vasprintf(3). + </para> + <para> + This function sets the name of the new pointer to the new + string. This is equivalent to: + </para> + <programlisting>talloc_set_name_const(ptr, ptr)</programlisting> + </refsect2> + <refsect2><title>char *talloc_asprintf(const void *<emphasis role="italic">t</emphasis>, const char *<emphasis role="italic">fmt</emphasis>, ...);</title> + <para> + The talloc_asprintf() function is the talloc equivalent of the C + library function asprintf(3). + </para> + <para> + This function sets the name of the new pointer to the passed + string. This is equivalent to: + </para> + <programlisting>talloc_set_name_const(ptr, ptr)</programlisting> + </refsect2> + <refsect2><title>char *talloc_asprintf_append(char *s, const char *fmt, ...);</title> + <para> + The talloc_asprintf_append() function appends the given formatted + string to the given string. + </para> + <para> + This function sets the name of the new pointer to the new + string. This is equivalent to: + </para> + <programlisting>talloc_set_name_const(ptr, ptr)</programlisting> + </refsect2> + <refsect2><title>(type *)talloc_array(const void *ctx, type, uint_t count);</title> + <para> + The talloc_array() macro is equivalent to: + </para> + <programlisting>(type *)talloc_size(ctx, sizeof(type) * count);</programlisting> + <para> + except that it provides integer overflow protection for the + multiply, returning NULL if the multiply overflows. + </para> + </refsect2> + <refsect2><title>void *talloc_array_size(const void *ctx, size_t size, uint_t count);</title> + <para> + The talloc_array_size() function is useful when the type is not + known. It operates in the same way as talloc_array(), but takes a + size instead of a type. + </para> + </refsect2> + <refsect2><title>(typeof(ptr)) talloc_array_ptrtype(const void *ctx, ptr, uint_t count);</title> + <para> + The talloc_ptrtype() macro should be used when you have a pointer to an array + and want to allocate memory of an array to point at with this pointer. When compiling + with gcc >= 3 it is typesafe. Note this is a wrapper of talloc_array_size() + and talloc_get_name() will return the current location in the source file. + and not the type. + </para> + </refsect2> + <refsect2><title>void *talloc_realloc_fn(const void *ctx, void *ptr, size_t size)</title> + <para> + This is a non-macro version of talloc_realloc(), which is useful + as libraries sometimes want a realloc function pointer. A + realloc(3) implementation encapsulates the functionality of + malloc(3), free(3) and realloc(3) in one call, which is why it is + useful to be able to pass around a single function pointer. + </para> + </refsect2> + <refsect2><title>void *talloc_autofree_context(void);</title> + <para> + This is a handy utility function that returns a talloc context + which will be automatically freed on program exit. This can be + used to reduce the noise in memory leak reports. + </para> + </refsect2> + <refsect2><title>void *talloc_check_name(const void *ptr, const char *name);</title> + <para> + This function checks if a pointer has the specified <emphasis + role="italic">name</emphasis>. If it does then the pointer is + returned. It it doesn't then NULL is returned. + </para> + </refsect2> + <refsect2><title>(type *)talloc_get_type(const void *ptr, type);</title> + <para> + This macro allows you to do type checking on talloc pointers. It + is particularly useful for void* private pointers. It is + equivalent to this: + </para> + <programlisting>(type *)talloc_check_name(ptr, #type)</programlisting> + </refsect2> + <refsect2><title>talloc_set_type(const void *ptr, type);</title> + <para> + This macro allows you to force the name of a pointer to be a + particular <emphasis>type</emphasis>. This can be + used in conjunction with talloc_get_type() to do type checking on + void* pointers. + </para> + <para> + It is equivalent to this: + </para> + <programlisting>talloc_set_name_const(ptr, #type)</programlisting> + </refsect2> + </refsect1> + <refsect1><title>PERFORMANCE</title> + <para> + All the additional features of talloc(3) over malloc(3) 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. + </para> + </refsect1> + <refsect1><title>SEE ALSO</title> + <para> + malloc(3), strndup(3), vasprintf(3), asprintf(3), + <ulink url="http://talloc.samba.org/"/> + </para> + </refsect1> + <refsect1><title>COPYRIGHT/LICENSE</title> + <para> + Copyright (C) Andrew Tridgell 2004 + </para> + <para> + 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. + </para> + <para> + 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. + </para> + <para> + You should have received a copy of the GNU General Public License + along with this program; if not, see http://www.gnu.org/licenses/. + </para> + </refsect1> +</refentry> |