sys_mman.h(0P)

💖 sys_mman.h — the POSIX memory management header, bestie edition 💖

okay so this one lives in the POSIX Programmer's Manual, and the page is literally called sys_mman.h(0P) — it's giving "the header file that holds all the memory-management declarations" energy. 🧠✨

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🚨 PROLOG 🚨

This manual page is part of the POSIX Programmer's Manual. Heads up though, bestie: the Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux. So like, don't come for me if your kernel does its own thing 💀

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🌸 NAME 🌸

sys/mman.h — memory management declarations. that's it, that's the vibe. 🫶

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✨ SYNOPSIS ✨

#include <sys/mman.h>

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👑 DESCRIPTION 👑

The <sys/mman.h> header shall define the following symbolic constants for use as protection options:

• PROT_EXEC — Page can be executed.
• PROT_NONE — Page cannot be accessed.
• PROT_READ — Page can be read.
• PROT_WRITE — Page can be written.

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The <sys/mman.h> header shall define the following symbolic constants for use as flag options:

• MAP_FIXED — Interpret addr exactly.
• MAP_PRIVATE — Changes are private.
• MAP_SHARED — Share changes.

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The <sys/mman.h> header shall define the following symbolic constants for the msync() function:

• MS_ASYNC — Perform asynchronous writes.
• MS_INVALIDATE — Invalidate mappings.
• MS_SYNC — Perform synchronous writes.

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The <sys/mman.h> header shall define the following symbolic constants for the mlockall() function:

• MCL_CURRENT — Lock currently mapped pages.
• MCL_FUTURE — Lock pages that become mapped.

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The <sys/mman.h> header shall define the symbolic constant MAP_FAILED which shall have type void * and shall be used to indicate a failure from the mmap() function. not me getting emotionally attached to a failure sentinel 😭

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If the Advisory Information option is supported, the <sys/mman.h> header shall define symbolic constants for the advice argument to the posix_madvise() function as follows:

• POSIX_MADV_DONTNEED — The application expects that it will not access the specified range in the near future.
• POSIX_MADV_NORMAL — The application has no advice to give on its behavior with respect to the specified range. It is the default characteristic if no advice is given for a range of memory.
• POSIX_MADV_RANDOM — The application expects to access the specified range in a random order.
• POSIX_MADV_SEQUENTIAL — The application expects to access the specified range sequentially from lower addresses to higher addresses.
• POSIX_MADV_WILLNEED — The application expects to access the specified range in the near future.

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The <sys/mman.h> header shall define the following symbolic constants for use as flags for the posix_typed_mem_open() function:

• POSIX_TYPED_MEM_ALLOCATE — Allocate on mmap().
• POSIX_TYPED_MEM_ALLOCATE_CONTIG — Allocate contiguously on mmap().
• POSIX_TYPED_MEM_MAP_ALLOCATABLE — Map on mmap(), without affecting allocatability.

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The <sys/mman.h> header shall define the mode_t, off_t, and size_t types as described in <sys_types.h>. ty for the types, <sys_types.h> 🫡

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The <sys/mman.h> header shall define the posix_typed_mem_info structure, which shall include at least the following member:

size_t  posix_tmi_length  Maximum length which may be allocated
                          from a typed memory object.

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The following shall be declared as functions and may also be defined as macros. Function prototypes shall be provided. here's the whole squad, no cap 👑

int    mlock(const void *, size_t);
int    mlockall(int);
void  *mmap(void *, size_t, int, int, int, off_t);
int    mprotect(void *, size_t, int);
int    msync(void *, size_t, int);
int    munlock(const void *, size_t);
int    munlockall(void);
int    munmap(void *, size_t);
int    posix_madvise(void *, size_t, int);
int    posix_mem_offset(const void *restrict, size_t, off_t *restrict,
           size_t *restrict, int *restrict);
int    posix_typed_mem_get_info(int, struct posix_typed_mem_info *);
int    posix_typed_mem_open(const char *, int, int);
int    shm_open(const char *, int, mode_t);
int    shm_unlink(const char *);

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The following sections are informative. (aka: not normative, just vibes) 💅

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🌈 APPLICATION USAGE 🌈

None. literally nothing. iconically empty. 🎀

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🦋 RATIONALE 🦋

None. also nothing. the void is stunning. ✨

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⭐ FUTURE DIRECTIONS ⭐

None. the future is a mystery and this section is not participating. 💀

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🔥 SEE ALSO 🔥

• <sys_types.h>
• The System Interfaces volume of POSIX.1‐2017, mlock(), mlockall(), mmap(), mprotect(), msync(), munmap(), posix_madvise(), posix_mem_offset(), posix_typed_mem_get_info(), posix_typed_mem_open(), shm_open(), shm_unlink()

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💜 COPYRIGHT 💜

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .

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okay and that's a wrap, bestie — this page is brought to you by IEEE/The Open Group, dated 2017, and it's filed under sys_mman.h(0P). slay, go touch some memory 🫶💖

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