如何在构建时用C断言前pressions [英] Ways to ASSERT expressions at build time in C

问题描述

我整理使用一些旧的code幻数各地设置硬件寄存器，我想使用常量，而不是这些数字，使code稍微更前的地方pressive（事实上，他们将映射到用于记录注册的名称/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).

不过，我担心有改动的量我可能打破幻数。下面是一个简化的例子（寄存器集是更复杂的）：

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;

所以不是：

set_register(5);

我们有：

set_register(state1|mode1);

我正在寻找的是一个建造时间的版本：

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

更新

@Christian，感谢您的快速反应，我很感兴趣的一个C /非增压的环境太回答，因为这是驱动/内核code。

@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

新的答案

在我原来的答复（见下文），我必须有两个不同的宏来支持一个函数范围，并在全球范围内的断言。我在想，如果有可能拿出一个解决方案，将在这两个领域的工作。

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.

我能找到工作了Visual Studio和科莫使用EXTERN的字符数组的编译器的解决方案。但我能找到一个更复杂的解决方案，为GCC的作品。但GCC的解决方案并不适用于Visual Studio工作。 :(但加入'的#ifdef __ __ GNUC'，很容易选择一个给定的编译器设置宏的权利。

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__ */

下面是报告 STATIC_ASSERT（1 == 1，test_message）的错误信息;在test.c的线路22 ：

GCC：

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

Visual Studio的：

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

科莫：

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

＆NBSP;＆搜索NBSP;结果

 
 

原来的答案

我做的非常相似，跳棋做一些事情。但是我包括消息，将在许多编译器显示：

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];          \
}

和在全球范围内做一些事情（在函数外）使用：

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]

这篇关于如何在构建时用C断言前pressions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IT屋！