sigaction 如何既是结构又是函数？

Question

我注意到 sigaction 被定义为结构和函数(http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/signal.h.html):

    int sigaction(int, const struct sigaction *restrict,
       struct sigaction *restrict);

使用它的一个例子是：

    struct sigaction sa;

    /* Set up handler */
    sa.sa_flags = SA_SIGINFO|SA_RESTART;
    sa.sa_sigaction = timer_expiry;

    /* Setup signal watchdog */
    if (sigaction(SIG_WDOG, &sa, NULL) == -1) {
       printf("ERROR: Failed to set wdog signal with %s",
           strerror(errno));
    }

Answer 1

C 有几个标识符的名称空间；函数标识符和结构标记标识符位于不同的名称空间中。

(C11, 6.2.3 Name spaces of identifiers p1) "If more than one declaration of a particular identifier is visible at any point in a translation unit, the syntactic context disambiguates uses that refer to different entities. Thus, there are separate name spaces for various categories of identifiers, as follows:

label names (disambiguated by the syntax of the label declaration and use);

the tags of structures, unions, and enumerations (disambiguated by following any32) of the keywords struct, union, or enum);

the members of structures or unions; each structure or union has a separate name space for its members (disambiguated by the type of the expression used to access the member via the . or -> operator);

all other identifiers, called ordinary identifiers (declared in ordinary declarators or as enumeration constants)

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sigaction 如何既是结构又是函数？

How can sigaction be both struct and function?

c

linux

unix

sigaction