在MS Visual C ++中启用VLA(可变长度数组)? [英] Enabling VLAs (variable length arrays) in MS Visual C++?
问题描述
如何在MS Visual C ++中启用VLA,C99中定义的可变长度数组,或者根本无法使用?
How can I enable the use of VLAs, variable length arrays as defined in C99, in MS Visual C++ or that is not possible at all?
是的,我知道C ++标准基于C89,并且VLA在C89标准中不可用,因此在C ++中不可用,但是MSVC ++也应该是C编译器,这种行为可以打开使用/TC编译器参数(Compile as C Code (/TC)
).但是这样做似乎并不能启用VLA,并且在编译时与C ++(Compile as C++ Code (/TP)
)相同的错误也会失败.也许MSVC ++ C编译器仅符合C89,或者我缺少某些内容(某些特殊构造或编译指示/定义)?
Yes I know that the C++ standard is based on C89 and that VLAs are not available in C89 standard and thus aren't available in C++, but MSVC++ is supposed to be a C compiler also, a behavior that can be switched on using the /TC compiler parameter (Compile as C Code (/TC)
). But doing so does not seem to enable VLAs and the compiling process fails with the same errors when building as C++ (Compile as C++ Code (/TP)
). Maybe MSVC++ C compiler is C89 compliant only or I am missing something (some special construct or pragma/define)?
代码示例:
#include <stdlib.h>
int main(int argc, char **argv)
{
char pc[argc+5];
/* do something useful with pc */
return EXIT_SUCCESS;
}
编译错误:
错误C2057:期望的常量表达式
error C2057: expected constant expression
错误C2466:无法分配大小恒定为0的数组
error C2466: cannot allocate an array of constant size 0
错误C2133:"pc":大小未知
error C2133: 'pc' : unknown size
推荐答案
MSVC不是C99编译器,并且不支持可变长度数组.
MSVC is not a C99 compiler, and does not support variable length arrays.
在 https://docs.microsoft.com/en -us/cpp/c-language/ansi-conformance MSVC被证明符合C90.
At https://docs.microsoft.com/en-us/cpp/c-language/ansi-conformance MSVC is documented as conforming to C90.
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