fopen和fclose？ [英] fopen and fclose?
问题描述
如果fopen失败，是否需要调用fclose？
我看到这样的例子：
....
stream = fopen（...）;
if（stream == NULL）
{
....
}
其他
{
....
}
fclose（stream）;
....
根据我的理解，它应该是这样的：
....
stream = fopen（...）;
if（stream == NULL）
{
....
}
其他
{
....
fclose（stream）;
}
if fopen failed, does it necessary to call fclose?
I see an example like this:
....
stream = fopen(...);
if(stream == NULL)
{
....
}
else
{
....
}
fclose(stream);
....
By my understanding, it should like this:
....
stream = fopen(...);
if(stream == NULL)
{
....
}
else
{
....
fclose(stream);
}
推荐答案
它应该是这样的：
stream = fopen（...）;
if（stream == NULL）
{
...
}
其他
{
...
fclose（stream）;
}
fclose''ing NULL指针未定义，可能会导致问题。
fclose只有它是一个流一个有效的开放流。
It should be like this:
stream = fopen(...);
if (stream == NULL)
{
...
}
else
{
...
fclose(stream);
}
fclose''ing a NULL pointer is undefined and could cause problems.
fclose a stream ONLY iff it is a valid open stream.
kathy写道：
如果fopen失败，是否有必要调用fclose？
使用空指针调用fclose并不会造成任何损害，如果无法关闭提供的话，
函数将返回错误代码
档。
我看到一个这样的例子：
...
stream = fopen（...）;
if （stream == NULL）
{
...
}
{
...
}
fclose （流）;
...
根据我的理解，它应该是这样的：
...
stream = fopen（...）;
if（stream == NULL）
{
...
}
{
...
fclose（流）;
}
if fopen failed, does it necessary to call fclose?
It doesn''t hurt anything to call fclose with a null pointer, and the
function will return an error code if it fails to close the supplied
file.
I see an example like this:
...
stream = fopen(...);
if(stream == NULL)
{
...
}
else
{
...
}
fclose(stream);
...
By my understanding, it should like this:
...
stream = fopen(...);
if(stream == NULL)
{
...
}
else
{
...
fclose(stream);
}
你的方式更可取，恕我直言，但我认为要么是合法的。更好的是
可能会改为使用std :: fstream。 :-)
干杯！ --M
Your way is preferable, IMHO, but I think either is legal. Better still
might be to use std::fstream instead. :-)
Cheers! --M
kathy写道：
如果fopen失败，是否有必要调用fclose？
编号实际上我找不到任何关于将要发生什么的描述
如果你将空指针传递给''fclose ''。结论：它未定义
行为，应该避免。 IOW，你必须_not_调用''fclose''来获取从''fopen'获得的
a指针，如果打开失败（并且空指针是
返回）。
[..]
if fopen failed, does it necessary to call fclose?
No. And actually I can''t find any description of what''s going to happen
if you pass a null pointer to ''fclose''. Conclusion: it''s undefined
behaviour and should be avoided. IOW, you must _not_ call ''fclose'' for
a pointer obtained from ''fopen'' if opening failed (and null pointer is
returned).
[..]
V
V
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