Question

在xcode中，在使用gcc编译应用程序时，如果NSZombieEnabled之类的东西用于分发版本，我想抛出编译时错误，从而确保编译失败并且我不会意外地做一些愚蠢的事情。

我做了一些谷歌搜索，但无法弄清楚如果满足某个条件，如何使编译器保释。当然它一定很容易，我只是找不到它？

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!"

由于NSZombieEnabled是一个环境变量，因此您需要在构建脚本中做一些聪明的事情，将宏定义为零或一个。

严格地说，#error指令发生在C预处理器中，而不是gcc。但在您描述的情况下，这应该不重要。

Answer 2

NSZombieEnabled是一个环境标志，据我所知，它不应该影响生成的二进制文件（尽管它可能会影响编译的速度。）

Answer 3

complile-time assert（） - a.k.a。静态断言 - 可能会有所帮助。这是我的，主要来自http://www.pixelbeat.org/programming/gcc/static_assert.html：

/*-----------------------------------------------------------------------------
 *  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)}

但我纠正了我对C ++ 0x中“无用”消息的看法：

/*-----------------------------------------------------------------------------
 *  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)]

Answer 4

您可以做的另一个有趣的事情是操纵构建脚本的输出。如果您在构建过程中使用自定义构建脚本，则可以执行以下操作：

echo "error: this build step failed!"

或者：

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

这些将产生错误或警告（分别），这些错误或警告将显示在构建结果窗口中。我已经使用了几次，而且真的很有用。

如何在GCC和Xcode中手动抛出编译器错误

4 个答案: