Re: static int prob ...
On Tue, 3 Feb 2009 20:01:24 -0500, "Tom" <johnthompson1@hotmail.com> wrote:
I have the following .h file:
static int x = 0;
class CMyClass
{
public:
static BOOL Test()
{
... code ...
x++;
... more code ...
}
static PUCHAR GetBuffer()
{
... code ...
for (int i = 0; i < x; i++)
{ ... do stuff ... }
}
}
So here's my problem,
I have an MFC app that I see come in and call the Test function first, and x
is incremented to 1. Later, another thread comes in and calls GetBuffer(),
and x is now equal to 0. Why?!
It's a static variable, and it is never decremented anywhere in any of my
code. Why is it different in the 2 different threads? Doesn't the static
mean that there is only 1 instance of it?
You have a copy of x in every source file that directly or indirectly
#includes the .h file that defines it. For this reason, it is almost always
an error to define a static variable in a header file. You may also have
synchronization errors due to multithreading. Also, to improve the design,
you should consider making x a static member of CMyClass.
--
Doug Harrison
Visual C++ MVP
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