Variable goes out of scope in the child thread when parent thread returns

[hanhao]

ok guys,
a quick newbie question:

how do i pass a variable into a thread when i still need that variable AFTER the parent thread returns. after hours of experimenting, i found the problem is when the parent thread returns, the variable in the child thread (formally passed by the parent thread) goes out of scope and disappears....

A few ideas i thought of

1) use static ?? i am now too sure on this

2) use a gobal variable?? i think it still goes out of scope too
anyway this is not very elegant method

3) anything???


in summary:
- a user interface thread starts a worker thread
- user interface thread returns so that the program doesnt freeze
- worker thread still needs to work around with the variable
<-- problem with the retaining of the variable when user interface thread goes out of scope


using
- visual c++ 6.0
- win98SE
- API, dont know much about MFC till i learn more on the basic APIs that make up MFC

[Yves M]

Use a pointer to memory dynamically allocated with new. Then you can destroy it whenever it's not needed anymore and you can keep it as long as you like.

[hanhao]

thnx for your valuable suggestion.
This is what i did:

char *thread_buffer;
thread_buffer = new char[];
thread_buffer = (*(start_thread_parm*)thread_parm).comd; // dynamically allocating the variable as suggested
SetEvent((*(start_thread_parm*)thread_parm).continue_broadcast_handle); // tells the parent thread that i have finished copying the parmeter to the child thread and it's ok to continue to return


This is the class of "start_thread_parm" summarized

class start_thread_parm{
public:
{
char *comd;
HANDLE continue_broadcast_handle;
}



is this the way to do it?
i keep getting the same problem when the parent thread returns, ie. the variable goes out of scope when the parent thread returns.
thread_buffer becomes empty after the line "SetEvent((*(start_thread_parm*)thread_parm).continue_broadcast_handle); "

I am doing something wrong here. any help plz?

[Andreas Masur]

[Moved thread]

[Andreas Masur]

Well...there are many information missing:

Where does 'thread_parm' gets allocated?
Where does 'thread_parm.comd' gets allocated?
How is the thread created?
How do you pass 'thread_parm'?
How do you cast them back inside the thread?
...

You need to dynamically allocate the data that you are passing to the thread...in other words, if 'start_thread_parm' is the class you want to pass to the thread, then you need to allocate one instance of that class dynamically...