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mallinfo.3: Document mallinfo2() and note that mallinfo() is deprecated
Document the mallinfo2() function added in glibc 2.33. Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
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Michael Kerrisk
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.\"
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.TH MALLINFO 3 2020-11-01 "Linux" "Linux Programmer's Manual"
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.SH NAME
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mallinfo \- obtain memory allocation information
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mallinfo, mallinfo2 \- obtain memory allocation information
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.SH SYNOPSIS
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.nf
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.B #include <malloc.h>
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.PP
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.B struct mallinfo mallinfo(void);
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.B struct mallinfo2 mallinfo2(void);
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.fi
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.SH DESCRIPTION
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The
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.BR mallinfo ()
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function returns a copy of a structure containing information about
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These functions return a copy of a structure containing information about
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memory allocations performed by
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.BR malloc (3)
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and related functions.
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The structure returned by each function contains the same fields.
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However, the older function,
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.BR mallinfo (),
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is deprecated since the type used for the fields is too small (see BUGS).
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.PP
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Note that not all allocations are visible to
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.BR mallinfo ();
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Note that not all allocations are visible to these functions;
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see BUGS and consider using
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.BR malloc_info (3)
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instead.
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.PP
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The returned structure is defined as follows:
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The
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.I mallinfo2
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structure returned by
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.BR mallinfo2 ()
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is defined as follows:
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.PP
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.in +4n
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.EX
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struct mallinfo {
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int arena; /* Non-mmapped space allocated (bytes) */
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int ordblks; /* Number of free chunks */
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int smblks; /* Number of free fastbin blocks */
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int hblks; /* Number of mmapped regions */
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int hblkhd; /* Space allocated in mmapped regions (bytes) */
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int usmblks; /* See below */
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int fsmblks; /* Space in freed fastbin blocks (bytes) */
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int uordblks; /* Total allocated space (bytes) */
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int fordblks; /* Total free space (bytes) */
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int keepcost; /* Top-most, releasable space (bytes) */
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struct mallinfo2 {
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size_t arena; /* Non-mmapped space allocated (bytes) */
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size_t ordblks; /* Number of free chunks */
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size_t smblks; /* Number of free fastbin blocks */
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size_t hblks; /* Number of mmapped regions */
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size_t hblkhd; /* Space allocated in mmapped regions
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(bytes) */
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size_t usmblks; /* See below */
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size_t fsmblks; /* Space in freed fastbin blocks (bytes) */
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size_t uordblks; /* Total allocated space (bytes) */
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size_t fordblks; /* Total free space (bytes) */
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size_t keepcost; /* Top-most, releasable space (bytes) */
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};
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.EE
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.in
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.PP
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The fields of the
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The
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.I mallinfo
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structure contain the following information:
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structure returned by the deprecated
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.BR mallinfo ()
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function is exactly the same, except that the fields are typed as
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.IR int .
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.PP
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The structure fields contain the following information:
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.TP 10
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.I arena
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The total amount of memory allocated by means other than
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@ -117,8 +131,13 @@ of the heap.
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This is the maximum number of bytes that could ideally
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(i.e., ignoring page alignment restrictions, and so on) be released by
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.BR malloc_trim (3).
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.\" .SH VERSIONS
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.\" Available already in glibc 2.0, possibly earlier
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.SH VERSIONS
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.\" mallinfo(): Available already in glibc 2.0, possibly earlier
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The
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.BR mallinfo2 ()
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function was added
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.\" commit e3960d1c57e57f33e0e846d615788f4ede73b945
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in glibc 2.33.
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.SH ATTRIBUTES
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For an explanation of the terms used in this section, see
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.BR attributes (7).
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@ -128,11 +147,13 @@ lb lb lbw28
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l l l.
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Interface Attribute Value
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T{
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.BR mallinfo ()
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.BR mallinfo (),
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.BR mallinfo2 ()
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T} Thread safety MT-Unsafe init const:mallopt
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.TE
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.sp 1
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.BR mallinfo ()
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.BR mallinfo ()/
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.BR mallinfo2 ()
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would access some global internal objects.
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If modify them with non-atomically,
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may get inconsistent results.
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@ -143,11 +164,14 @@ in
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mean that
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.BR mallopt ()
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would modify the global internal objects with atomics, that make sure
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.BR mallinfo ()
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.BR mallinfo ()/
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.BR mallinfo2 ()
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is safe enough, others modify with non-atomically maybe not.
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.SH CONFORMING TO
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This function is not specified by POSIX or the C standards.
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A similar function exists on many System V derivatives,
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These functions are not specified by POSIX or the C standards.
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A
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.BR mallinfo ()
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function exists on many System V derivatives,
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and was specified in the SVID.
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.SH BUGS
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.\" FIXME . http://sourceware.org/bugzilla/show_bug.cgi?id=208
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@ -164,7 +188,9 @@ for alternatives that include information about other arenas.
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.PP
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The fields of the
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.I mallinfo
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structure are typed as
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structure that is returned by the older
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.BR mallinfo ()
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function are typed as
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.IR int .
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However, because some internal bookkeeping values may be of type
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.IR long ,
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