我问了一个问题here关于assert
它在标准中作为宏实现,而不是函数。
这给我带来了一个问题,因为 assert
似乎是一个函数,它采用参数:assert(true)
因此我尝试使用它是:std::assert(true)
,当然这是一个不起作用的宏。
我的问题是:标准库是否提供了任何其他宏,它们会显示为带有参数的函数?
最佳答案
如果我们看一下 [headers] 第 5 段和第 6 段,我们会发现
Names which are defined as macros in C shall be defined as macros in the C++ standard library, even if C grants license for implementation as functions. [ Note: The names defined as macros in C include the following:
assert
,offsetof
,setjmp
,va_arg
,va_end
, andva_start
. —end note ]Names that are defined as functions in C shall be defined as functions in the C++ standard library.
因此,如果它在 C 中定义为宏,那么它在 C++ 中也将是宏。但也有一些异常(exception)。来自 [support.runtime] 第 7 和 8 段
The header
<cstdalign>
and the header<stdalign.h>
shall not define a macro namedalignas
.The header
<cstdbool>
and the header<stdbool.h>
shall not define macros namedbool
,true
, orfalse
.
尽管 [headers]/7 也涵盖了这些异常(exception)情况
Identifiers that are keywords or operators in C++ shall not be defined as macros in C++ standard library headers.
还有一个异常(exception),即 7.12.3 分类宏中定义的所有分类宏都可以按 [c.math]/10 的函数重载
The classification/comparison functions behave the same as the C macros with the corresponding names defined in 7.12.3, Classification macros, and 7.12.14, Comparison macros in the C Standard. Each function is overloaded for the three floating-point types, as follows:
int fpclassify(float x); bool isfinite(float x); bool isinf(float x); bool isnan(float x); bool isnormal(float x); bool signbit(float x); bool isgreater(float x, float y); bool isgreaterequal(float x, float y); bool isless(float x, float y); bool islessequal(float x, float y); bool islessgreater(float x, float y); bool isunordered(float x, float y); int fpclassify(double x); bool isfinite(double x); bool isinf(double x); bool isnan(double x); bool isnormal(double x); bool signbit(double x); bool isgreater(double x, double y); bool isgreaterequal(double x, double y); bool isless(double x, double y); bool islessequal(double x, double y); bool islessgreater(double x, double y); bool isunordered(double x, double y); int fpclassify(long double x); bool isfinite(long double x); bool isinf(long double x); bool isnan(long double x); bool isnormal(long double x); bool signbit(long double x); bool isgreater(long double x, long double y); bool isgreaterequal(long double x, long double y); bool isless(long double x, long double y); bool islessequal(long double x, long double y); bool islessgreater(long double x, long double y); bool isunordered(long double x, long double y);
关于c++ - 什么标准调用实际上是宏,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/44369648/