CALLOC(3POSIX)

💖 CALLOC — a memory allocator 💖

okay bestie, welcome to CALLOC(3POSIX) from the POSIX Programmer's Manual 🌸 this is the glow-up of a classic and you're gonna eat it up, no cap.

---

✨ PROLOG ✨

so real talk first 🫶 this manual page is part of the POSIX Programmer's Manual. but heads up — the Linux implementation of this interface may differ (go check the corresponding Linux manual page for the tea on Linux behavior), or honestly the interface may not be implemented on Linux at all. not every baddie is available everywhere 💅

---

🌈 NAME 🌈

calloc — a memory allocator 👑

---

🎀 SYNOPSIS 🎀

#include <stdlib.h>

void *calloc(size_t nelem, size_t elsize);

---

💜 DESCRIPTION 💜

okay so the functionality described on this reference page is aligned with the ISO C standard. if there's any conflict between the requirements here and the ISO C standard, that's unintentional fr fr — this volume of POSIX.1‐2017 defers to the ISO C standard. periodt.

The calloc() function shall allocate unused space for an array of nelem elements, each of whose size in bytes is elsize. and the space shall be initialized to all bits 0 ✨ (yes bestie, zeroed out, squeaky clean, that's the whole vibe).

The order and contiguity of storage allocated by successive calls to calloc() is unspecified. okay so here's the part where you gotta pay attention 👀 The pointer returned if the allocation succeeds shall be suitably aligned so that it may be assigned to a pointer to any type of object and then used to access such an object, or an array of such objects, in the space allocated (until the space is explicitly freed or reallocated). Each such allocation shall yield a pointer to an object disjoint from any other object. The pointer returned shall point to the start — that's the lowest byte address — of the allocated space. If the space cannot be allocated, a null pointer shall be returned.

and now the iconic chaotic part 🌀 If the size of the space requested is 0, the behavior is implementation-defined: either a null pointer shall be returned, or the behavior shall be as if the size were some non-zero value, except that the behavior is undefined if the returned pointer is used to access an object. so like… it's giving "you got a pointer maybe, but do NOT touch anything with it" 💀

---

💅 RETURN VALUE 💅

Upon successful completion with both nelem and elsize non-zero, calloc() shall return a pointer to the allocated space. yay 🎉

If either nelem or elsize is 0, then either:

• A null pointer shall be returned and errno may be set to an implementation-defined value, or
• A pointer to the allocated space shall be returned. The application shall ensure that the pointer is not used to access an object.

Otherwise, it shall return a null pointer and set errno to indicate the error. 😭

---

🔥 ERRORS 🔥

The calloc() function shall fail if:

• ENOMEM — Insufficient memory is available. (ran out of room bestie, it happens 🥲)

The following sections are informative. 👑

---

🦋 EXAMPLES 🦋

None. (yes literally none, the page said what it said 💀)

---

🍓 APPLICATION USAGE 🍓

There is now no requirement for the implementation to support the inclusion of <malloc.h>. so don't come for it 🫶

---

🌸 RATIONALE 🌸

None. iconic minimalism 💅

---

⭐ FUTURE DIRECTIONS ⭐

None.

---

👑 SEE ALSO 👑

• free()
• malloc()
• realloc()

The Base Definitions volume of POSIX.1‐2017, <stdlib.h>

---

💖 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 .

---

and that's the whole page bestie 🎀 this little love letter was brought to you by IEEE/The Open Group, 2017 — go forth, allocate responsibly, and remember: calloc zeroes your bytes but it will NOT zero out your problems 😭💜 mwah 🫶✨