<stdlib.h> 之间的区别和 <malloc.h> [英] difference between <stdlib.h> and <malloc.h>

问题描述

当我在 C 程序中使用 malloc 时，收到警告:

When I use malloc in a C program, I get a warning:

warning: incompatible implicit declaration of built-in function 'malloc' [enabled by default]

然后我可以包含 或 以摆脱 warning 尽管它有效也没有它.

I can then include <malloc.h> or <stdlib.h> to get rid of the warning although it works without it as well.

所以我想知道，当我不包含任何内容时，这些标题与 gcc 链接的标题之间有什么区别?

So I was wondering, what's the difference between these headers and which one does gcc links when I don't include anything?

(我使用 ubuntu 12.04 64 位 和 gcc 4.6.3)

推荐答案

<malloc.h> 标头已弃用(并且非常特定于 Linux，它定义了非标准 函数类似于 mallinfo(3)).如果您只需要 malloc(3) 和相关的标准函数(例如 free、calloc、realloc ....).请注意， 由 C89 定义(和后来)标准，但不是

The <malloc.h> header is deprecated (and quite Linux specific, on which it defines non-standard functions like mallinfo(3)). Use <stdlib.h> instead if you simply need malloc(3) and related standard functions (e.g. free, calloc, realloc ....). Notice that <stdlib.h> is defined by C89 (and later) standards, but not <malloc.h>

查看 /usr/include/malloc.h 你会发现那里有一些非标准函数(例如 malloc_stats(3) 等...) - 除了 malloc....

Look into /usr/include/malloc.h you'll find there some non-standard functions (e.g. malloc_stats(3), etc...) - in addition of malloc....

和 gcc 不链接头文件，而是链接库.阅读 Levine 的关于 linkers & 的书加载器了解更多.

And gcc don't link header files, but libraries. Read Levine's book about linkers & loaders for more.

如果您不包含任何标头(并且没有自己显式声明 malloc，这将是一个坏主意)，malloc 被隐式声明为返回一些 int 值(这是错误的).我确实邀请您在使用它时至少将 -Wall 标志传递给 gcc.

If you don't include any headers (and dont explicitly declare malloc yourself, which would be a bad idea), malloc is implicitly declared as returning some int value (which is wrong). I do invite you to pass at least the -Wall flag to gcc when using it.

您也可以将 -v 传递给 gcc 以了解所涉及的实际程序:cc1 是正确的编译器(生成汇编代码)，as 汇编器，ld 链接器，以及 collect2 一个调用链接器的内部实用程序.

You might also pass -v to gcc to understand the actual programs involved: cc1 is the compiler proper (producing assembly code), as the assembler, ld the linker, and collect2 an internal utility which invokes the linker.

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