如何在GCC和Xcode中手動拋出編譯器錯誤

Question

在xcode中，當使用gcc編譯應用程序時，如果NSZombieEnabled之類的東西在分發版本上運行，我想拋出編譯時間錯誤，從而確保編譯失敗，不小心做了一些愚蠢的事情。

我做了一些Google搜索，但無法弄清楚如何在符合某些條件時讓編譯器保釋。當然，它一定很容易，我只是沒有找到它？

Answer 1

使用the #error directive：

#if SHOULD_FAIL 
#error "bad compiler!" 
#endif 

int main() 
{ 
    return 0; 
} 

 
$ gcc a.c -DSHOULD_FAIL=0 # passes fine 
$ gcc a.c -DSHOULD_FAIL=1 
a.c:2:2: error: #error "bad compiler!" 

由於NSZombieEnabled是一個環境變量，你需要做一些聰明的你構建腳本來定義宏爲0或1。

嚴格地說，#error指令發生在C預處理器中，而不是gcc。但在你描述的情況下，這應該不重要。

Answer 2

NSZombieEnabled是一個環境標誌和，據我所知，應該不會影響到生成的二進制文件（儘管它可能影響編譯的速度。）

Answer 3

你可以做另一個有趣的事情是操縱你的編譯器的輸出腳本。如果您正在使用自定義構建腳本作爲構建過程的一部分，你可以這樣做：

echo "error: this build step failed!" 

或者：

echo "warning: this build step could be potentially faulty" 

那些會產生（分別）錯誤或警告，將顯示在構建結果窗口中打開。我已經使用了幾次，並且它的確很有用。

Answer 4

complile-time assert（） - a.k.a。靜態斷言 - 可能會有所幫助。這裏是我的，從http://www.pixelbeat.org/programming/gcc/static_assert.html主要衍生：

/*----------------------------------------------------------------------------- 
* Compile-time ASSERT(). Similar to the BOOST_STATIC_ASSERT(). And the C++0x 
* static_assert(), which also has a parameter for a useless error message 
* (see correction!). Our ASSERT() can be placed anywhere in the code, except: 
* 
* o In a twice-included header file, without a #ifndef...#endif wrapper. 
* o In the middle of a structure definition (or enum definition). 
* o In C89 or C90, after a statement. But you can wrap it in braces! 
* 
* If you want stick something in the middle of a structure definition 
* you'll need to use the ugly, three-line construct #if...#error...#endif. 
* And if you do do this, the pre-processor has a much more limited idea of 
* what a "constant expression" is. 
* 
* This is a refinement of ideas from the web (www.pixebeat.org is good). It 
* is shorter than BOOST. And, I believe, is better than Linus Torvald's 
* suggestion for an improved BUILD_BUG_ON(). And the do{...}while(0) wrapper 
* you commonly see is totally inapplicable here: it limits permissible 
* locations. 
* 
* The web has many suggestions using arrays with a negative index. But with 
* GCC, most of these do not detect a NON-CONSTANT arg (which is easy enough 
* to do in error), except for the attractive 'extern int foo[expression]', 
* which also gives an 'unused variable' warning (which might be fixable via 
* (void)foo). GCC 4.3 apparently has a built-in static_assert(). Update: 
* typedef int array[expression] seems also to be good. 
*/ 
#define CONCAT_TOKENS(a, b) a ## b 
#define EXPAND_THEN_CONCAT(a,b) CONCAT_TOKENS(a, b) 
#define ASSERT(e) enum {EXPAND_THEN_CONCAT(ASSERT_line_,__LINE__) = 1/!!(e)} 

但我糾正了在C '無用' 的消息我看來++ 0x中：

/*----------------------------------------------------------------------------- 
* Correction!: The message in static_assert() isn't quite useless, and we've 
* added it to ASSERTM(). This is needed for the case where two different 
* header files happen by chance to have two ASSERT()'s on the same line, or 
* likewise for a source file and a header file. 
* 
* We could also handle this via __COUNTER__, but this isn't supported by 
* the SGI compiler (and is uglier). And we can't use __FILE__, because it 
* doesn't usually expand to a valid C token (e.g. it has a dot c or dot h). 
*/ 
#define ASSERTM(e,m) enum{EXPAND_THEN_CONCAT(m##_ASSERT_line_,__LINE__)=1/!!(e)} 

一些例子：

/*----------------------------------------------------------------------------- 
* Example: 
*/ 
ASSERTM (sizeof (int16) == 2, my_global_header_h); 
ASSERTM (sizeof (ord32) == 4, my_global_header_h); 
ASSERTM (sizeof (int64) == 8, my_global_header_h); 

/*----------------------------------------------------------------------------- 
* Equally good, I believe, is the following variant, but it is slightly 
* longer (and not used by us at the present time): 
*/ 
#define ASSERTt(e) typedef int EXPAND_THEN_CONCAT(ASSERT_line_,__LINE__)[1-2*!(e)]