宏执行整数运算 [英] Macro perform integer arithmetic

问题描述

是否可以使用宏执行算术运算(对于我的情况是乘法)?

Is it possible to perform arithmetic (multiplication for my case) using macros?

据我所知，写一个宏像:

I understand that writing a macro like:

#define mult(a,b) ((a)*(b))

会到处替代产品.但是我两个参数都是常量.我知道，编译器也将静态执行乘法运算，但问题是，我使用#将结果转换为字符串.

Will substitute the product everywhere. But I have both my parameters as constants. I know the compiler will also perform the multiplication statically, but the issue is that I have to convert the result to a string using #.

有什么想法可以做到吗?

Any idea how it can be done?

此外，如果它能够与C ++宏来完成，我仍是好的.我可以写在C ++那些特定的模块和连接起来.

Also if it can be done with C++ macros, I am still okay. I can write those particular modules in C++ and link it up.

以下是我本代码

#define ARG_COPY()      __asm__("subq   $8, %rsp"); \
                        __asm__("movq   %gs:0xe8, %r10"); \
                        __asm__("movq   $16, %r11"); \
                        __asm__("1:"); \
                        __asm__("movq   -8(%r10, %r11, 8), %rax"); \
                        __asm__("pushq  %rax"); \
                        __asm__("decq   %r11"); \
                        __asm__("jne    1b"); \

#define ARG_REMOVE()    __asm__("add    $136, %rsp"); 

现在上面的代码被写入没有参数 - 136是16×8 + 8.我想使该16的参数.相同的16设置在第一宏太使用.

Now the above code is written without arguments - the 136 is 16 * 8 + 8. I want to make that 16 a parameter. The same 16 is used in the first macro too.

推荐答案

没有. C预处理器仅对令牌进行操作(通过将一个令牌序列替换为另一令牌序列).两者之间不做算术运算.

No. The C preprocessor operates purely on tokens (by replacing one token sequence with another). It does not do arithmetic in between.

您必须编写自己的一种预处理的这一点.还是用产品字符串创建头文件，并在需要的地方包含#include呢?另一种可能性:不要打扰;如果不是真正的性能瓶颈，请使用sprintf(s, "%d", mult(a,b));.也许某些编译器 足够聪明，可以在编译时对其进行评估.

You would have to write your own kind of preprocessor for this. Or what about creating header file with the product strings and #including it where needed? Yet another possibility: don't bother; if it's not truly a performance bottleneck, use sprintf(s, "%d", mult(a,b));. Maybe some compiler is smart enough to evaluate this at compile time.

有多少产品不断的字符串，你呢?他们中有多少不同?

How many constant product strings do you have? How many of them are different?

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