问题描述
内存使用在我的应用程序是相当关键。因此，我有具体的断言，在编译时检查内存大小，并给出一个static_assert如果大小不同于我们认为正确之前。
我已经定义了一个宏像这样：
#define CHECKMEM（mytype，size）static_assert（（sizeof（objectType）== size）不正确的#mytype！）;
这个宏可以很容易写成：
CHECKMEM（Book，144）;
CHECKMEM（图书馆，80）;
问题是当这个static_assert关闭时，可能很难找出什么新的size应该是（例如通过使用隐藏的编译器选项/ d1 reportAllClassLayout）。
如果我可以包括实际大小，那么会更加方便，因此代替：
会显示
我尝试这样写：
#define CHECKMEM（mytype，size）static_assert（（sizeof（objectType）== size）），size incorrect for#mytype！ is#sizeof（mytype）））;
但是你不能在函数调用上使用stringize
我也试过添加双字符串技巧，如下所示：
#define STR1（x）#x
#define STR2（x）STR1（x）
#define CHECKMEM（mytype，size）static_assert（sizeof（objectType）== size） #mytype！（预期为#size，大小为STR2（sizeof（mytype））））;
但不是打印 size is 152 打印 size是sizeof（Book）。
有没有办法在static_assert中stringize结果sizeof？
我将在函数模板上使用dispatching来执行检查：
#include< cstddef>
template< typename ToCheck，std :: size_t ExpectedSize，std :: size_t RealSize = sizeof（ToCheck）>
void check_size（）{
static_assert（ExpectedSize == RealSize，Size is off！）;
}
struct foo
{
char bla [16];
};
int main（）
{
check_size< foo，8>（）;
return 0;
}
结果：
在实例化'void check_size（）[with ToCheck = foo; long unsigned int ExpectedSize = 8ul; long unsigned int RealSize = 16ul]'：
bla.cpp：15：22：从这里需要
bla.cpp：5：1：error：static assertion failed：Size is off！
调试信息在回溯的模板参数中。
如果这真的更好，你必须决定，它还取决于编译器。它还允许您使用模板映射隐藏预期大小，总计到最大大小和其他奇异的东西。
Memory usage is quite critical in my application. Therefore I have specific asserts that check for the memory size at compile time and give a static_assert if the size is different from what we considered correct before.
I have defined a macro like this:
#define CHECKMEM(mytype, size) static_assert((sizeof(objectType) == size)), "Size incorrect for " #mytype "!");
This macro makes it very easy to write this:
CHECKMEM(Book,144);
CHECKMEM(Library,80);
The problem is that when this static_assert goes off, it might be quite difficult to find out what the new size should be (e.g. by using the hidden compiler option "/d1 reportAllClassLayout").It would be much handier if I could include the actual size, so instead of:
It would show
I tried writing something like this:
#define CHECKMEM(mytype, size) static_assert((sizeof(objectType) == size)), "Size incorrect for " #mytype "! (expected" #size ", size is " #sizeof(mytype) ")");
But you can't use the stringize (#) operator on a function call.
I also tried adding the double-stringize trick, like this:
#define STR1(x) #x
#define STR2(x) STR1(x)
#define CHECKMEM(mytype, size) static_assert((sizeof(objectType) == size)), "Size incorrect for " #mytype "! (expected" #size ", size is " STR2(sizeof(mytype)) ")");
But instead of printing size is 152 it prints size is sizeof(Book).
Is there a way to stringify the result of sizeof in a static_assert?
I'd use dispatching on a function template to do the checking:
#include <cstddef>
template <typename ToCheck, std::size_t ExpectedSize, std::size_t RealSize = sizeof(ToCheck)>
void check_size() {
static_assert(ExpectedSize == RealSize, "Size is off!");
}
struct foo
{
char bla[16];
};
int main()
{
check_size<foo, 8>();
return 0;
}
Results in:
In instantiation of ‘void check_size() [with ToCheck = foo; long unsigned int ExpectedSize = 8ul; long unsigned int RealSize = 16ul]’:
bla.cpp:15:22: required from here
bla.cpp:5:1: error: static assertion failed: Size is off!
The debugging information is in the template parameters of the back-trace.
If this is truly better, you will have to decide and it also depends on the compiler. It also enables you to hide the expected size with a template map, to sum up to a max size and other fancy things.
这篇关于如何结合static_assert与sizeof和stringify？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！