Hello everyone,
From MSDN, http://msdn2.microsoft.com/en-us/library/ms682583.aspx
parameter fdwReason of DllMain has four values,
DLL_PROCESS_ATT ACH
DLL_PROCESS_DET ACH
DLL_THREAD_ATTA CH
DLL_THREAD_DETA CH
I think we could simply understand what MSDN described about the four values
in the following way after some experiment (I have read the big table and
want to extract some brief and simple information to understand to remember),
DLL_PROCESS_ATT ACH: will be called only once when the process loads the DLL
for the 1st time
DLL_PROCESS_DET ACH: will be called only once when the process unloads the
DLL (when process stops)
DLL_THREAD_ATTA CH: will be called every time when a thread inside the
current process loads the DLL
DLL_THREAD_DETA CH: will be called every time when a thread inside the
current process unloads the DLL
Is that correct understanding?
thanks in advance,
George 10  2351 
>Is that correct understanding?
Yes that's essentially it - to the best of my understanding of course.
Dave
George,
DLL_THREAD_ATTA CH will be called for every already loaded DLL when a new
thread is created. (This allows the DLL to setup things like thread local
storage). There is no requirement for the thread to load the DLL. Similarly
for DLL_THREAD_DETA CH - every loaded DLL is called when the thread exits.
Bob
"George" <Ge****@discuss ions.microsoft. comwrote in message
news:92******** *************** ***********@mic rosoft.com...
Hello everyone,
From MSDN,
http://msdn2.microsoft.com/en-us/library/ms682583.aspx
parameter fdwReason of DllMain has four values,
DLL_PROCESS_ATT ACH
DLL_PROCESS_DET ACH
DLL_THREAD_ATTA CH
DLL_THREAD_DETA CH
I think we could simply understand what MSDN described about the four
values
in the following way after some experiment (I have read the big table and
want to extract some brief and simple information to understand to
remember),
DLL_PROCESS_ATT ACH: will be called only once when the process loads the
DLL
for the 1st time
DLL_PROCESS_DET ACH: will be called only once when the process unloads the
DLL (when process stops)
DLL_THREAD_ATTA CH: will be called every time when a thread inside the
current process loads the DLL
DLL_THREAD_DETA CH: will be called every time when a thread inside the
current process unloads the DLL
Is that correct understanding?
thanks in advance,
George
"George" <Ge****@discuss ions.microsoft. comwrote in message
news:92******** *************** ***********@mic rosoft.com...
Hello everyone,
From MSDN,
http://msdn2.microsoft.com/en-us/library/ms682583.aspx
parameter fdwReason of DllMain has four values,
DLL_PROCESS_ATT ACH
DLL_PROCESS_DET ACH
DLL_THREAD_ATTA CH
DLL_THREAD_DETA CH
I think we could simply understand what MSDN described about the four
values
in the following way after some experiment (I have read the big table and
want to extract some brief and simple information to understand to
remember),
DLL_PROCESS_ATT ACH: will be called only once when the process loads the
DLL
for the 1st time
DLL_PROCESS_DET ACH: will be called only once when the process unloads the
DLL (when process stops)
No, these are wrong (others have explained the THREAD messages).
If LoadLibrary and FreeLibrary are used, then DLL_PROCESS_ATT ACH is called
each time the use count changes from 0 to 1 and DLL_PROCESS_DET ACH is called
each time the use count changes from 1 to 0. This could happen multiple
times in a single run.
Thanks Bob,
It is interesting and after reading MSDN reference, I think each time a new
thread is created, DllMain will be invoked (as callback function) with
DLL_THREAD_ATTA CH value (support DLL is loaded before creating thread) --
even if the thread does not use the DLL at all, right?
regards,
George
"Bob Milton" wrote:
George,
DLL_THREAD_ATTA CH will be called for every already loaded DLL when a new
thread is created. (This allows the DLL to setup things like thread local
storage). There is no requirement for the thread to load the DLL. Similarly
for DLL_THREAD_DETA CH - every loaded DLL is called when the thread exits.
Bob
"George" <Ge****@discuss ions.microsoft. comwrote in message
news:92******** *************** ***********@mic rosoft.com...
Hello everyone,
From MSDN,
http://msdn2.microsoft.com/en-us/library/ms682583.aspx
parameter fdwReason of DllMain has four values,
DLL_PROCESS_ATT ACH
DLL_PROCESS_DET ACH
DLL_THREAD_ATTA CH
DLL_THREAD_DETA CH
I think we could simply understand what MSDN described about the four
values
in the following way after some experiment (I have read the big table and
want to extract some brief and simple information to understand to
remember),
DLL_PROCESS_ATT ACH: will be called only once when the process loads the
DLL
for the 1st time
DLL_PROCESS_DET ACH: will be called only once when the process unloads the
DLL (when process stops)
DLL_THREAD_ATTA CH: will be called every time when a thread inside the
current process loads the DLL
DLL_THREAD_DETA CH: will be called every time when a thread inside the
current process unloads the DLL
Is that correct understanding?
thanks in advance,
George
Hi David,
I think my previous understanding has some mistakes. I think if a process
calls LoadLibrary again for the DLL after the DLL is already loaded, DllMain
will be invoked again with DLL_PROCESS_ATT ACH value, right?
regards,
George
"David Lowndes" wrote:
Is that correct understanding?
Yes that's essentially it - to the best of my understanding of course.
Dave
Thanks Ben,
I think you mean if we have already load the library, if we call LoadLibrary
again and again, the DllMain will not be called again and again since the
reference counter is already >1, right?
But if the process unloads the DLL (make reference counter to 0), then
LoadLibrary again, the DllMain will be called again with DLL_PROCESS_ATT ACH
value, right?
regards,
George
"Ben Voigt [C++ MVP]" wrote:
>
"George" <Ge****@discuss ions.microsoft. comwrote in message
news:92******** *************** ***********@mic rosoft.com...
Hello everyone,
From MSDN,
http://msdn2.microsoft.com/en-us/library/ms682583.aspx
parameter fdwReason of DllMain has four values,
DLL_PROCESS_ATT ACH
DLL_PROCESS_DET ACH
DLL_THREAD_ATTA CH
DLL_THREAD_DETA CH
I think we could simply understand what MSDN described about the four
values
in the following way after some experiment (I have read the big table and
want to extract some brief and simple information to understand to
remember),
DLL_PROCESS_ATT ACH: will be called only once when the process loads the
DLL
for the 1st time
DLL_PROCESS_DET ACH: will be called only once when the process unloads the
DLL (when process stops)
No, these are wrong (others have explained the THREAD messages).
If LoadLibrary and FreeLibrary are used, then DLL_PROCESS_ATT ACH is called
each time the use count changes from 0 to 1 and DLL_PROCESS_DET ACH is called
each time the use count changes from 1 to 0. This could happen multiple
times in a single run.
>I have such questions after reading Ben's answer,
>
>If LoadLibrary and FreeLibrary are used, then DLL_PROCESS_ATT ACH is called
each time the use count changes from 0 to 1 and DLL_PROCESS_DET ACH is
called each time the use count changes from 1 to 0. This could happen multiple
times in a single run.
Yes it's reasonable that if a process unloads a DLL and then re-loads
it, it's not really different to the initial load situation, so you
would expect the process attach notification.
Dave
I agree, thanks Dave.
regards,
George
"David Lowndes" wrote:
I have such questions after reading Ben's answer,
If LoadLibrary and FreeLibrary are used, then DLL_PROCESS_ATT ACH is called
each time the use count changes from 0 to 1 and DLL_PROCESS_DET ACH is
called each time the use count changes from 1 to 0. This could happen multiple
times in a single run.
Yes it's reasonable that if a process unloads a DLL and then re-loads
it, it's not really different to the initial load situation, so you
would expect the process attach notification.
Dave
"George" <Ge****@discuss ions.microsoft. comwrote in message
news:E3******** *************** ***********@mic rosoft.com...
Thanks Ben,
I think you mean if we have already load the library, if we call
LoadLibrary
again and again, the DllMain will not be called again and again since the
reference counter is already >1, right?
But if the process unloads the DLL (make reference counter to 0), then
LoadLibrary again, the DllMain will be called again with
DLL_PROCESS_ATT ACH
value, right?
I think that is correct, yes.
>
regards,
George
"Ben Voigt [C++ MVP]" wrote:
>>
"George" <Ge****@discuss ions.microsoft. comwrote in message
news:92******* *************** ************@mi crosoft.com...
Hello everyone,
From MSDN,
http://msdn2.microsoft.com/en-us/library/ms682583.aspx
parameter fdwReason of DllMain has four values,
DLL_PROCESS_ATT ACH
DLL_PROCESS_DET ACH
DLL_THREAD_ATTA CH
DLL_THREAD_DETA CH
I think we could simply understand what MSDN described about the four
values
in the following way after some experiment (I have read the big table
and
want to extract some brief and simple information to understand to
remember),
DLL_PROCESS_ATT ACH: will be called only once when the process loads the
DLL
for the 1st time
DLL_PROCESS_DET ACH: will be called only once when the process unloads
the
DLL (when process stops)
No, these are wrong (others have explained the THREAD messages).
If LoadLibrary and FreeLibrary are used, then DLL_PROCESS_ATT ACH is
called
each time the use count changes from 0 to 1 and DLL_PROCESS_DET ACH is
called
each time the use count changes from 1 to 0. This could happen multiple
times in a single run.
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