return（i = 1，NULL） [英] return (i = 1, NULL)
问题描述
这是合法的：
FILE * func（无效）{
extern int errno;
return（errno = EINVAL，NULL）;
}
我的编译器（openbsd上的gcc 2.9.x）抱怨我回来了
来自int w / oa cast的指针。然而，linux上的gcc 3.x从来没有对它进行窥视
，所以可能2.9.x只是脾气暴躁。
i假设相关的问题是，可以分一组不同的类型，比如
那个？
tia，
比尔
Ben Pfaff< bl*@cs.stanford.edu>写道：William Ahern< wi ***** @ wilbur.25thandClement.com>写道：
这是合法的：
FILE * func（void）{
extern int errno;
返回（errno = EINVAL，NULL）;
}
编号你不能自己声明`errno''那样的（它不一定是变量）而你忘了#include< stdio.h>。
如果你解决了这两个问题，那么是的。
是的。是的。*
如果你解决了这两个问题，那么是的。
这就是我的想法。比如。
- 比尔
* - http://www.ebaumsworld.com/arnolds3.html
William Ahern <无线***** @ wilbur.25thandClement.com>在消息新闻中写道：36 ************ @ wilbur.25thandClement.com ...这是合法的：
FILE * func （void）{
extern int errno;
返回（errno = EINVAL，NULL）;
}
我的编译器（gcc 2.9.x on openbsd）抱怨说我正在从int w / oa cast返回一个
指针。然而，linux上的gcc 3.x从来没有对它有过窥视，所以2.9.x可能只是脾气暴躁。
为了避免讨论名称空间污染，让我改写
你的代码：
FILE * func（无效）
{
extern int my_errno;
return（my_errno = SOME_VALUE，NULL）;
}
并且给return语句赋予的表达式不是常量
表达式，因为它包含逗号运算符。因此，在返回的
* full *表达式中，NULL不符合null
指针常量。如果你的实现#defines NULL只是为0（或
类似的类型与FILE *不兼容的那些），
你的程序是非法的，这就是gcc抱怨。
-
Jun，Woong（my******@hanmail.net）
< blockquote> William Ahern< wi ***** @ wilbur.25thandClement.com>在消息新闻中写道：< 36 ************ @ wilbur.25thandClement.com> ...
这是合法的：
FILE * func（void）{
extern int errno;
返回（errno = EINVAL，NULL）;
}
我的编译器（gcc 2.9 .x on openbsd）抱怨我从int w / oa cast返回了一个
指针。然而，Linux上的gcc 3.x从来没有对它进行过深入了解，所以可能2.9.x只是脾气暴躁。
编译器错误。顺便说一下，return语句不需要（）。
Sam
is this legal:
FILE *func(void) {
extern int errno;
return (errno = EINVAL, NULL);
}
my compiler (gcc 2.9.x on openbsd) is complaining that i''m returning a
pointer from int w/o a cast. gcc 3.x on linux, however, never made a peep
about it, so possibly 2.9.x is just grumpy.
i suppose the relevent question is, can one group different types like
that?
tia,
Bill
Ben Pfaff <bl*@cs.stanford.edu> wrote:William Ahern <wi*****@wilbur.25thandClement.com> writes:is this legal:
FILE *func(void) {
extern int errno;
return (errno = EINVAL, NULL);
}
No. You can''t declare `errno'' yourself like that (it''s not
necessarily a variable) and you forgot to #include <stdio.h>. If you fix those two problems, then yes.
yes. yeah.*
If you fix those two problems, then yes.
that''s what i thought. thanx.
- Bill
* - http://www.ebaumsworld.com/arnolds3.html
"William Ahern" <wi*****@wilbur.25thandClement.com> wrote in message news:36************@wilbur.25thandClement.com...is this legal:
FILE *func(void) {
extern int errno;
return (errno = EINVAL, NULL);
}
my compiler (gcc 2.9.x on openbsd) is complaining that i''m returning a
pointer from int w/o a cast. gcc 3.x on linux, however, never made a peep
about it, so possibly 2.9.x is just grumpy.
To avoid the discussion on the name space pollution, let me rewrite
your code:
FILE *func(void)
{
extern int my_errno;
return (my_errno = SOME_VALUE, NULL);
}
And the expression given to the return statement is not a constant
expression, becuase it contains the comma operator. Therefore, in the
*full* expression for the return, NULL doesn''t qualify as a null
pointer constant. If your implementation #defines NULL simply as 0 (or
similar ones whose types are not assignment-compatible with FILE *),
your program is illegal, which is what gcc complains about.
--
Jun, Woong (my******@hanmail.net)
William Ahern <wi*****@wilbur.25thandClement.com> wrote in message news:<36************@wilbur.25thandClement.com>...is this legal:
FILE *func(void) {
extern int errno;
return (errno = EINVAL, NULL);
}
my compiler (gcc 2.9.x on openbsd) is complaining that i''m returning a
pointer from int w/o a cast. gcc 3.x on linux, however, never made a peep
about it, so possibly 2.9.x is just grumpy.
Compiler bug. The return statement does not require ( ), incidentally.
Sam
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