以下程序是否符合严格的C99计划？

概述标题几乎说明了一切,但我会重申这个问题…… 以下程序是否符合C99标准的“严格符合程序”？ #include <stdlib.h>/* Removing any pre-existing macro definition, in case one should exist in the implementation. * Seems to be allowed under 7.1.3 para 标题几乎说明了一切,但我会重申这个问题……

以下程序是否符合C99标准的“严格符合程序”？

#include <stdlib.h>/* Removing any pre-existing macro deFinition,in case one should exist in the implementation. * Seems to be allowed under 7.1.3 para 3,as malloc does not begin with _X where X is any  cAPItal letter. * And 7.1.4 para 1 explicitly permits #undef of such macros. */#ifdef malloc    #undef malloc     #endif            /* Macro substitution has no impact on the external name malloc * which remains accessible,e.g.,via "(malloc)(s)".  Such use of * macro substitution seems enabled by 7.1.4 para 1,but not specifically * mentioned otherwise. */voID * journalling_malloc(size_t size);#define malloc(s)     ((journalling_malloc)(s))      int main(voID){    return malloc(10) == NulL ? 1 : 0;         /* Just for the sake of expanding the      * macro one time,return as exit code     * whether the allocation was performed.      */}

解决方法 让我们来看看C99标准对它的看法：

见第7节7.1.3,§1：

Each IDentifIEr with file scope Listed in any of the following subclauses […] is reserved for use as a macro name and as an IDentifIEr with file scope in the same name space if any of its associated headers is included.

当您包含stdlib.h时,名称malloc保留用作宏名称.

但是7.1.4,§1允许在保留名称上使用#undef：

The use of #undef to remove any macro deFinition will also ensure that an
actual function is referred to.

这使得可以重新定义malloc,根据7.1.3,§2导致未定义的行为：

If the program […] defines a reserved IDentifIEr as a macro name,the behavior is undefined.

为什么标准会制定此限制？因为标准库的其他函数可以在原始函数方面实现为类函数宏,所以隐藏声明可能会破坏这些其他函数.

实际上,只要你的malloc定义满足标准为库函数提供的所有规定,你就应该没问题,这可以通过将实际调用包装到malloc()来实现.

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