内存中的程序布局（是否覆盖了我的静态指针？） [英] Program layout in memory (is anything overwriting my static pointer?)
问题描述
我已经完成了在我们的产品中整理崩溃的工作
我们有崩溃信息和事件的avi（
不可能匹配，但稍后更多......）（顺便说一下这是一个单独的
线程VC9 / win32应用程序）
错误的调用堆栈有效进行
void * myBuf;
void myFunc（ ）
{
if（myBuf）
{
（这里可能会发生一些事情）
用myBuf做一些事情..除了调试中的'NULL'
我有b $ b信息
}
我的问题是..堆中的任何东西都可以覆盖myBuf
NULL？
另一个可能性是另一个静态变量，比如一个固定大小的数组
我们在界外写作。
我的老板刚刚告诉我，我们正在使用名为Smartheap的内存管理器，
垃圾知道那是什么正在做..
有何评论？
Hi,
I''ve been given the job of sorting out a crash in our product for
which we have the crash information and an avi of the event (which
can''t possibly match but more of that later...) (btw this is a single
threaded VC9 / win32 app)
The call stack for the bug effectively goes
void* myBuf;
void myFunc()
{
if( myBuf )
{
(maybe some stuff happens here)
do something with myBuf.. except it''s NULL in the debug
information I have
}
My question is.. can anything in the heap have overwritten myBuf with
NULL?
Another possibilty is another static variable, say a fixed size array
where we''re writing outside the bounds.
My boss just told me we''re using a memory manager called Smartheap,
crap knows what that''s doing..
Any comments?
推荐答案
simonl写道：
simonl wrote:
我已经完成了整理产品崩溃的工作
我们有崩溃信息和事件的avi（
不可能匹配，但后来更多......）（顺便说一下这是一个单一的
线程VC9 / win32应用程序）
错误的调用堆栈有效地进行了
void * myBuf;
void myFunc（）
{
if（myBuf）
{
Hi,
I''ve been given the job of sorting out a crash in our product for
which we have the crash information and an avi of the event (which
can''t possibly match but more of that later...) (btw this is a single
threaded VC9 / win32 app)
The call stack for the bug effectively goes
void* myBuf;
void myFunc()
{
if( myBuf )
{
}
我的问题是..堆中的任何东西都可以用
$ b覆盖myBuf $ b NULL？
}
My question is.. can anything in the heap have overwritten myBuf with
NULL?
一堆？如果您的应用程序是线程化的并且对myBuf的写入是无保护的，那么任何事情都可能发生。 myBuf不是静态的，它是全球的。
-
Ian Collins。
One the heap? If your application is threaded and writes to myBuf are
unguarded, anything might happen. myBuf isn''t static, its global.
--
Ian Collins.
simonl写道：
simonl wrote:
我已经完成了整理产品崩溃的工作
我们有崩溃信息和事件的avi
（这不可能匹配但后来更多......）（btw
这是一个单线程VC9 / win32应用程序）
错误的调用堆栈有效地进行了
void * myBuf ;
void myFunc（）
{
if（myBuf）
{
（也许这里发生了一些事情）
用myBuf做一些事情..除了它在调试中是NULL
我有的信息
}
我的问题是..堆中的任何东西都可以被覆盖
myBuf是否为NULL？
另一个可能性是另一个静态变量，比如说修复ed size
数组我们在界外写作。
我的老板刚刚告诉我我们正在使用一个名为
Smartheap，废话知道那是做什么的。
有何评论？
Hi,
I''ve been given the job of sorting out a crash in our product
for which we have the crash information and an avi of the event
(which can''t possibly match but more of that later...) (btw
this is a single threaded VC9 / win32 app)
The call stack for the bug effectively goes
void* myBuf;
void myFunc()
{
if( myBuf )
{
(maybe some stuff happens here)
do something with myBuf.. except it''s NULL in the debug
information I have
}
My question is.. can anything in the heap have overwritten
myBuf with NULL?
Another possibilty is another static variable, say a fixed size
array where we''re writing outside the bounds.
My boss just told me we''re using a memory manager called
Smartheap, crap knows what that''s doing..
Any comments?
测试NULL！= myBuf（注意在C中你应该总是测试
明确地反对NULL宏，它可能被定义为不
在所有系统上的值为0，0xffffffff可能是常见的，
只是告诉你指针是否已被标记为无效/ NIL
明确地说。然而它并没有告诉你它是否有效。
你可能有一个完美的非NULL指针，它仍然没有
指向有效的内存。
最终你希望myBuf在没有初始化时为NULL。
（大）惊喜：变量不是初始化
明确可以获得任何值，直到获得一个值。
所以将这两个更改添加到您的程序中，看看它是否有效
然后：
- 无效* myBuf;
+ void * myBuf = NULL;
- if（myBuf）
+ if（NULL！= myBuf）
您可以尝试用调试器测试程序，设置一个手表
myBuf上的
，看看它何时发生变化。
Wolfgang Draxinger
-
电子邮件地址作品，Jabber： he******@jabber.org ，ICQ：134682867
Testing for NULL != myBuf (note in C you should always test
against the NULL macro explicitly, it may be defined as not
being of value 0 on all systems, 0xffffffff may be as common),
just tells you if the pointer has been marked invalid/NIL
explicitly. It doesn''t tell you however if it''s valid.
You may have a perfectly non-NULL pointer, that''s still not
pointing into valid memory.
Eventually you expect myBuf to be NULL if it''s not initialized.
(Big) surprise though: Variables not being initialized
explicitly can have any value until getting a value assigned.
So add these two changes to your program, and see if it works
then:
- void* myBuf;
+ void *myBuf = NULL;
- if( myBuf )
+ if( NULL != myBuf )
And you might try test your program with a debugger, set a watch
on myBuf, to see when it changes.
Wolfgang Draxinger
--
E-Mail address works, Jabber: he******@jabber.org, ICQ: 134682867
Wolfgang Draxinger< wd * *******@darkstargames.dewrote：
Wolfgang Draxinger <wd********@darkstargames.dewrote:
测试NULL！= myBuf（在C中注意你应该总是测试
明确地反对NULL宏，它可能被定义为不是所有系统上的值为0的b $ b，0xffffffff可能是常见的，
Testing for NULL != myBuf (note in C you should always test
against the NULL macro explicitly, it may be defined as not
being of value 0 on all systems, 0xffffffff may be as common),
这是胡说八道。值为零的常量整数表达式
（例如，ooh，可能为0）将_always_ compare等于空指针，
，无论该空指针如何表示在记忆中;和一个布尔值
对任何标量的测试，包括指针，_always_就好像它被写为包含！= 0。
Richard
This is nonsense. A constant integer expression with the value zero
(such as, ooh, perhaps 0) will _always_ compare equal to a null pointer,
no matter how that null pointer is represented in memory; and a boolean
test against any scalar, including pointers, _always_ happens as if it
was written to include !=0.
Richard
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