可以定义__STDC_VERSION__吗？ [英] Is it ok to define __STDC_VERSION__?
问题描述
我目前使用的编译器会在以下语句中发出警告：
#if defined（__ STDC_VERSION__）|| __STDC_VERSION__< 19990601L
....
#endif
编译器抱怨__STDC_VERSION__没有定义。很明显
并没有使表达式短路，而是评估
||的两边。作为解决方法，我将语句改为：
#if！defined（__ STDC_VERSION__）
#define __STDC_VERSION__ 0
#endif
#if __STDC_VERSION__< 19990601L
....
#endif
除了任何拼写错误，在用户代码中定义__STDC_VERSION__是否合法？
-
boa
libclc home： http://libclc.sourceforge.net
< blockquote> Bj？Augestad写道：
我目前使用的编译器会在以下语句中发出警告：
#if已定义（__ STDC_VERSION__）|| __STDC_VERSION__< 19990601L
...
#endif
编译器抱怨__STDC_VERSION__没有定义。它显然不会使表达式短路，而是评估
||的两个方面。 [...]
如果没有定义__STDC_VERSION__那么应该如此。
你确定你在
测试表达式的开头没有错过`！''吗？
#if！defined（__ STDC_VERSION__）|| ...
^
-
Er ********* @ sun.com
2003年7月11日星期五，[ISO-8859-1] Bj？Augestad写道：
我目前使用的编译器会在以下语句中发出警告：
#if defined（__ STDC_VERSION__） || __STDC_VERSION__< 19990601L
...
#endif
编译器抱怨__STDC_VERSION__没有定义。它显然不会使表达式短路，而是评估
||的两个方面。作为一种解决方法，我将语句改为：
#if！defined（__ STDC_VERSION__）
#define __STDC_VERSION__ 0
#endif
#if __STDC_VERSION__< 19990601L
...
#endif
除了任何拼写错误，在用户代码中定义__STDC_VERSION__是否合法？
Hallvard亲切地追踪了使这个
无效的标准。但是，一个等价但合法的解决方法是
#ifndef __STDC_VERSION__
#define C_VERSION_NUMBER 0
#else
#define C_VERSION_NUMBER __STDC_VERSION__
#endif
#if C_VERSION_NUMBER< 19990601L
....
#endif
或其他任何行。
请注意，您的编译器可能会抱怨__STDC_VERSION __'不是
被定义，但如果它实际上拒绝编译您的程序，因为
这个，它'这不符合标准的不止一种方式。
我自己也赞同尽可能摆脱最无害的b $ b无害警告的想法。 />
-Arthur
Eric Sosman写道：
Bj？rn Augestad写道：
我目前使用的编译器会在以下语句中发出警告：
#if defined（__ STDC_VERSION__）|| __STDC_VERSION__< 19990601L
...
#endif
编译器抱怨__STDC_VERSION__没有定义。它显然不会使表达式短路，而是评估
||的两个方面。 [...]
如果没有定义__STDC_VERSION__那么应该如此。你确定在测试表达式的开头你没有错过`！''吗？
#if！defined（__ STDC_VERSION__）|| ...
^
我向所有已经回复原帖的人道歉，其中有一个
非常草率和不正确问题的插图。对于一些愚蠢的原因我决定编写代码而不是从源代码复制它
文件，我甚至混合了来自_POSIX_C_SOURCE的元素。 Duh。
这是造成问题的确切代码。它来自libclc文件
clc_settings.h并导致os20嵌入式操作系统的st20cc交叉编译器v.1.9.6
（windows版本）出现问题：
/ *处理C89和C99之间的差异* /
#if！defined __STDC_VERSION__ || __STDC_VERSION__< 199901L
#define CLC_RESTRICT
#else
#define CLC_RESTRICT restrict
#endif
再次感谢所有人。我将在星期一试用更多的编译器
并尝试提供一个便携且可行的解决方案。
-
boa
libclc home： http：// libclc .sourceforge.net
Hi,
I currently use a compiler which emits a warning on the following statement:
#if defined(__STDC_VERSION__) || __STDC_VERSION__ < 19990601L
....
#endif
The compiler complains that __STDC_VERSION__ isn''t defined. It obviously
doesn''t short circuit the expression, but evaluates both sides of the
||. I have, as a workaround, changed the statements into this:
#if !defined(__STDC_VERSION__)
#define __STDC_VERSION__ 0
#endif
#if __STDC_VERSION__ < 19990601L
....
#endif
Apart from any typos, is it legal to define __STDC_VERSION__ in user code?
--
boa
libclc home: http://libclc.sourceforge.net
Bj?rn Augestad wrote:
Hi,
I currently use a compiler which emits a warning on the following statement:
#if defined(__STDC_VERSION__) || __STDC_VERSION__ < 19990601L
...
#endif
The compiler complains that __STDC_VERSION__ isn''t defined. It obviously
doesn''t short circuit the expression, but evaluates both sides of the
||. [...]
As it should, if __STDC_VERSION__ isn''t defined. Are
you sure you''re not missing a `!'' at the beginning of the
test expression?
#if !defined(__STDC_VERSION__) || ...
^
--
Er*********@sun.com
On Fri, 11 Jul 2003, [ISO-8859-1] Bj?rn Augestad wrote:
I currently use a compiler which emits a warning on the following statement:
#if defined(__STDC_VERSION__) || __STDC_VERSION__ < 19990601L
...
#endif
The compiler complains that __STDC_VERSION__ isn''t defined. It obviously
doesn''t short circuit the expression, but evaluates both sides of the
||. I have, as a workaround, changed the statements into this:
#if !defined(__STDC_VERSION__)
#define __STDC_VERSION__ 0
#endif
#if __STDC_VERSION__ < 19990601L
...
#endif
Apart from any typos, is it legal to define __STDC_VERSION__ in user code?
Hallvard has kindly tracked down the bit of the standard that makes this
invalid. However, an equivalent but legal workaround would be
#ifndef __STDC_VERSION__
#define C_VERSION_NUMBER 0
#else
#define C_VERSION_NUMBER __STDC_VERSION__
#endif
#if C_VERSION_NUMBER < 19990601L
....
#endif
or anything along those lines.
Note that your compiler may be complaining about __STDC_VERSION__''s not
being defined, but if it actually refuses to compile your program because
of this, it''s not conforming to the Standard in more than one way.
I myself also subscribe to the idea of getting rid of even the most
harmless warnings, though.
-Arthur
Eric Sosman wrote:
Bj?rn Augestad wrote:Hi,
I currently use a compiler which emits a warning on the following statement:
#if defined(__STDC_VERSION__) || __STDC_VERSION__ < 19990601L
...
#endif
The compiler complains that __STDC_VERSION__ isn''t defined. It obviously
doesn''t short circuit the expression, but evaluates both sides of the
||. [...]
As it should, if __STDC_VERSION__ isn''t defined. Are
you sure you''re not missing a `!'' at the beginning of the
test expression?
#if !defined(__STDC_VERSION__) || ...
^
My apologies to all that has answered the original post, which had a
very sloppy and incorrect illustration of the problem. For some stupid
reason I decided to write the code instead of copying it from the source
file, and I even mixed in elements from _POSIX_C_SOURCE. Duh.
Here is the exact code causing problems. It''s from the libclc file
clc_settings.h and causes problems on the st20cc cross compiler v. 1.9.6
(windows version) for the os20 embedded os:
/* Handle differences between C89 and C99 */
#if !defined __STDC_VERSION__ || __STDC_VERSION__ < 199901L
# define CLC_RESTRICT
#else
# define CLC_RESTRICT restrict
#endif
Thanks again to all. I''ll experiment more with the compiler on monday
and try to come up with a portable and working solution.
--
boa
libclc home: http://libclc.sourceforge.net
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