逻辑或行为 [英] Behavior of logical or
问题描述
您好！
我在linux debian上运行gcc 2.95，并且遇到了一些奇怪的
行为。
我有这样一个表达式：
if（
* charVariable ==" \0"
||
strncmp（charVariable，anotherCharVariable，2）== 0
）
{
//做某事
}
当charVariable为null时，我希望构造不要尝试评估下一个子表达式的
。在我看来它确实如此，
导致分段错误。
是否可以控制这种行为？
Michael
" michaelp" < mi ****** @ hio.nowrote in message
news：eh ********** @ dolly.uninett.no ...
< blockquote class =post_quotes>
你好！
我在linux debian上运行gcc 2.95，并且遇到了一些奇怪的
行为。
我有这样一个表达式：
if（
* charVariable ==" \0" ;
||
strncmp（charVariable，anotherCharVariable，2）== 0
）
{
//做点什么
}
当charVariable为null时，我希望构造不要尝试
评估下一个子表达式。在我看来它确实如此，在分段错误中产生了
。
是否可以控制这种行为？
您是否尝试测试charVariable是否指向空字符''\0''或
如果它是空引用？你的代码暗示你正在尝试
前者，你的解释暗示你正在尝试后者。
michaelp写道：
你好！
我在linux debian上运行gcc 2.95，并且遇到了一些奇怪的
行为。
我有这样一个表达式：
if（
* charVariable ==" ; \0"
这可能是错误的。" \0"评估为指针。比较字符串
和strcmp。
如果你想要chech，那么charVariable是一个NULL指针，你会这样做b $ b $
charVariable == NULL
如果你想检查它是一个空字符串，你会这样做
* charVariable ==''\ 0''
或者charVariable [0] == 0
||
strncmp（charVariable，an otherCharVariable，2）== 0
）
{
//做点什么
}
当charVariable为null时，我希望构造不要尝试评估下一个子表达式的
。在我看来它确实如此，
导致分段错误。
是否可以控制这种行为？
Michael
On 25.10.2006 08:47，Nils O. Sel？sdal写道：
* charVariable ==''\'''
这就是我实际在做的事情。我在
消息中笨拙地表达了自己。 * charVariable ==" \0"当然是垃圾。
M.
Hello!
I am running gcc 2.95 on linux debian, and have come across some strange
behavior.
I have an expression like this:
if (
*charVariable == "\0"
||
strncmp(charVariable, anotherCharVariable, 2) == 0
)
{
//do something
}
When charVariable is null, I expect the construct not to attempt at
evaluating the next sub-expression. It seems to me that it does,
resulting in a segmentation fault.
Is it possible to control this behavior?
Michael
"michaelp" <mi******@hio.nowrote in message
news:eh**********@dolly.uninett.no...Hello!
I am running gcc 2.95 on linux debian, and have come across some strange
behavior.
I have an expression like this:
if (
*charVariable == "\0"
||
strncmp(charVariable, anotherCharVariable, 2) == 0
)
{
//do something
}
When charVariable is null, I expect the construct not to attempt at
evaluating the next sub-expression. It seems to me that it does, resulting
in a segmentation fault.
Is it possible to control this behavior?Are you trying to test if charVariable points to the null character ''\0'' or
if it is a null reference? Your code insinuates that you''re trying the
former, your explanation insinuates you''re trying the latter.
michaelp wrote:Hello!
I am running gcc 2.95 on linux debian, and have come across some strange
behavior.
I have an expression like this:
if (
*charVariable == "\0"This is likely wrong. "\0" evaluates to a pointer. Compare strings
with strcmp.
If you want to chech wether charVariable is a NULL pointer you''d
do
charVariable == NULL
if you want to check wether it is an empty string, you''d do
*charVariable == ''\0''
or perhaps charVariable[0] == 0
||
strncmp(charVariable, anotherCharVariable, 2) == 0
)
{
//do something
}
When charVariable is null, I expect the construct not to attempt at
evaluating the next sub-expression. It seems to me that it does,
resulting in a segmentation fault.
Is it possible to control this behavior?
Michael
On 25.10.2006 08:47, Nils O. Sel?sdal wrote:
*charVariable == ''\0''This is what I am actually doing. I expressed myself clumsily in the
message. *charVariable == "\0" is rubbish, of course.
M.
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