David Scarlett写道：

以下代码是否安全？


No.

SomeType * a，* b;

/ *部分代码.... * /

免费（a）;

if（a == b）b = NULL;

a = NULL;

SomeType * a，* b;


/ *有些代码...... * /


if（ a == b）b = NULL;


免费（a）;


a = NULL;


-

pete

On Sun，2004年5月16日03:25:21 GMT，pete< pf **** *@mindspring.com>写道：

David Scarlett写道：

以下代码是否安全？
否。

嗯。假设a在free（）之前有效且b仍然在比较的

点，我不明白为什么你认为这是不安全的。

个人在它之后测试指针的值似乎很奇怪

已被释放（并且你的版本在这个意义上更为传统），

但是因为我们是只测试/ pointer /而不是试图访问

它指向的内存，为什么OP的代码不是安全？

-leor

SomeType * a，* b;

/ *有些代码.... * /

免费（ a）;

if（a == b）b = NULL;

a = NULL;

SomeType * a， * b;

/ *有些代码.... * /

if（a == b）b = NULL;

免费（ a）;

a = NULL;

David Scarlett写道：

以下代码是否安全？


No.

SomeType * a，* b;

/ *部分代码.... * /

免费（a）;


该标准未规定是否更改了。它可能仍然

包含相同的值，它可能设置为NULL，或者它可能是一些

其他该死的值。


if（a == b）b = NULL;


相当无比的比较，对吧？

a = NULL;

谢谢。

Is the following code safe?

SomeType *a, *b;

/* Some code.... */

free(a);

if ( a == b ) b = NULL;

a = NULL;

Thanks.

--
David Scarlett

dscarlett@_ _ _ _ _ _ _ _
_ _ _ _ _ optusnet.com.au

David Scarlett wrote:

Is the following code safe?
No.
SomeType *a, *b;

/* Some code.... */

free(a);

if ( a == b ) b = NULL;

a = NULL;

SomeType *a, *b;

/* Some code.... */

if ( a == b ) b = NULL;

free(a);

a = NULL;

--
pete

On Sun, 16 May 2004 03:25:21 GMT, pete <pf*****@mindspring.com> wrote:

David Scarlett wrote:

Is the following code safe?
No.

Hmmm. Assuming a was valid before the free() and b still is at the
point of the comparison, I don''t get why you think this is unsafe.
Personally, it seems strange to test the value of a pointer after it
has been freed (and your version is more conventional in that sense),
but since we''re only testing the /pointer/ and not trying to access
the memory it is pointing to, why wouldn''t the OP''s code be "safe"?
-leor

SomeType *a, *b;

/* Some code.... */

free(a);

if ( a == b ) b = NULL;

a = NULL;

SomeType *a, *b;

/* Some code.... */

if ( a == b ) b = NULL;

free(a);

a = NULL;

David Scarlett wrote:

Is the following code safe?
No.
SomeType *a, *b;

/* Some code.... */

free(a);
The standard does not specify whether a is changed. It might still
contain the same value, it might be set to NULL, or it might be some
other damn value.

if ( a == b ) b = NULL;
Pretty pointless comparison, huh?

a = NULL;

Thanks.