> For the complete documentation index, see [llms.txt](https://book.bsdcn.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://book.bsdcn.org/man/stdbit/stdc_bit_ceil.3.md).

# stdc\_bit\_ceil.3

`stdc_bit_ceil` — 向上取整到下一个 2 的幂

## 名称

`stdc_bit_ceil`

## 概要

`Lb libc`

```c
#include <stdbit.h>
```

```c
unsigned char stdc_bit_ceil_uc(unsigned char value);
unsigned short stdc_bit_ceil_us(unsigned short value);
unsigned int stdc_bit_ceil_ui(unsigned int value);
unsigned long stdc_bit_ceil_ul(unsigned long value);
unsigned long long stdc_bit_ceil_ull(unsigned long long value);
typeof(value) stdc_bit_ceil(value);
```

## 描述

`stdc_bit_ceil_`*type*() 函数族将 `value` 向上取整到下一个 2 的幂，其中 `value` 的类型分别为 `unsigned char`、`unsigned short`、`unsigned int`、`unsigned long` 或 `unsigned long long`，对应 *type* 为 **uc**、**us**、**ui**、**ul** 或 **ull**。类型通用宏 `stdc_bit_ceil`(*value*) 根据 `value` 的类型选择适当的 `stdc_bit_ceil_`*type*() 函数。

## 返回值

返回 `value` 向上取整到下一个 2 的幂的结果。如果该值无法表示，则返回 0。

## 参见

[stdbit(3)](https://github.com/FreeBSD-Ask/freebsd-man-sc/tree/main/stdbit/stdbit.3.md), [stdc\_bit\_floor(3)](/man/stdbit/stdc_bit_floor.3.md)

## 标准

`stdc_bit_ceil_`*type*() 函数族和 `stdc_bit_ceil` 类型通用宏遵循 -isoC-2023 标准。

## 历史

`stdc_bit_ceil_`*type*() 函数族和 `stdc_bit_ceil` 类型通用宏在 FreeBSD 15.1 中添加。

## 作者

Robert Clausecker <fuz@FreeBSD.org>


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://book.bsdcn.org/man/stdbit/stdc_bit_ceil.3.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.