在 C 中构建时断言表达式的方法 [英] Ways to ASSERT expressions at build time in C

问题描述

我正在整理一些旧代码，这些代码到处使用幻数"来设置硬件寄存器，我想使用常量而不是这些数字来使代码更具表现力(实际上它们会映射用于记录寄存器的名称/值).

I'm tidying up some older code that uses 'magic numbers' all over the place to set hardware registers, and I would like to use constants instead of these numbers to make the code somewhat more expressive (in fact they will map to the names/values used to document the registers).

但是，我担心随着更改量的增加，我可能会打破魔幻数字.下面是一个简化的例子(寄存器组更复杂):

However, I'm concerned that with the volume of changes I might break the magic numbers. Here is a simplified example (the register set is more complex):

const short mode0 = 0;
const short mode1 = 1;
const short mode2 = 2;

const short state0 = 0;
const short state1 = 4;
const short state2 = 8;

所以而不是:

set_register(5);

我们有:

set_register(state1|mode1);

我正在寻找的是构建时间版本:

ASSERT(5==(state1|mode1));

更新

@Christian，感谢您的快速回复，我对 C/非增强环境的回答也很感兴趣，因为这是驱动程序/内核代码.

@Christian, thanks for the quick response, I'm interested on a C / non-boost environment answer too because this is driver/kernel code.

推荐答案

新答案:

在我的原始答案(如下)中，我必须有两个不同的宏来支持函数作用域和全局作用域中的断言.我想知道是否有可能想出一个在两个范围内都适用的解决方案.

In my original answer (below), I had to have two different macros to support assertions in a function scope and at the global scope. I wondered if it was possible to come up with a single solution that would work in both scopes.

我找到了一个适用于使用外部字符数组的 Visual Studio 和 Comeau 编译器的解决方案.但是我能够找到适用于 GCC 的更复杂的解决方案.但是 GCC 的解决方案不适用于 Visual Studio.:( 但是添加'#ifdef __ GUC __'，很容易为给定的编译器选择正确的宏集.

I was able to find a solution that worked for Visual Studio and Comeau compilers using extern character arrays. But I was able to find a more complex solution that works for GCC. But GCC's solution doesn't work for Visual Studio. :( But adding a '#ifdef __ GNUC __', it's easy to choose the right set of macros for a given compiler.

解决方案:

#ifdef __GNUC__
#define STATIC_ASSERT_HELPER(expr, msg) 
    (!!sizeof  (struct { unsigned int STATIC_ASSERTION__##msg: (expr) ? 1 : -1; }))
#define STATIC_ASSERT(expr, msg) 
    extern int (*assert_function__(void)) [STATIC_ASSERT_HELPER(expr, msg)]
#else
    #define STATIC_ASSERT(expr, msg)   
    extern char STATIC_ASSERTION__##msg[1]; 
    extern char STATIC_ASSERTION__##msg[(expr)?1:2]
#endif /* #ifdef __GNUC__ */

以下是为 STATIC_ASSERT(1==1, test_message); 报告的错误消息，位于 test.c 的第 22 行:

Here are the error messages reported for STATIC_ASSERT(1==1, test_message); at line 22 of test.c:

海湾合作委员会:

line 22: error: negative width in bit-field `STATIC_ASSERTION__test_message'

Visual Studio:

test.c(22) : error C2369: 'STATIC_ASSERTION__test_message' : redefinition; different subscripts
    test.c(22) : see declaration of 'STATIC_ASSERTION__test_message'

Comeau:

line 22: error: declaration is incompatible with
        "char STATIC_ASSERTION__test_message[1]" (declared at line 22)

 
 

 
 

原始答案:

我做的事情与 Checkers 所做的非常相似.但我添加了一条消息，该消息将出现在许多编译器中:

I do something very similar to what Checkers does. But I include a message that'll show up in many compilers:

#define STATIC_ASSERT(expr, msg)               
{                                              
    char STATIC_ASSERTION__##msg[(expr)?1:-1]; 
    (void)STATIC_ASSERTION__##msg[0];          
}

为了在全局范围内(在函数之外)做一些事情，使用这个:

And for doing something at the global scope (outside a function) use this:

#define GLOBAL_STATIC_ASSERT(expr, msg)   
  extern char STATIC_ASSERTION__##msg[1]; 
  extern char STATIC_ASSERTION__##msg[(expr)?1:2]

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