createMutex

[NewsArchive]

Hi Friedrich,

what are the correct Parameter Types for the Windows function
CreateMutex (
http://msdn.microsoft.com/en-us/library/ms682411(VS.85).aspx )?

I tried *LONG,INT,*STRING (and a few other combinations) with the
Function Parameters 0,0,%MUTEX_NAME%, but I get WinLastError 87 (
http://msdn.microsoft.com/en-us/library/windows/desktop/ms681382(v=vs.85).aspx
) very often (but not every time) on WinXP x86 SP2.

Thanks for your help.

Markus

[NewsArchive]

Markus,

Is there a problem with the "Create Named Mutex..." script function?

Friedrich

[NewsArchive]

Hi Friedrich,

a) I was not aware of it.

b) It returns every time "504" or "508" as Errorcode and in the given
variable, no matter, how many instances I run.

Screenshot attached.

Markus

[NewsArchive]

Hi Markus,

See: http://www.lindersoft.com/projects/createcheckmutex.zip

1. Compile and start CreateMutex.sb7

2. Compile and start CheckMutex.sb7

If CreateMutex.exe is active, CheckMutex.exe displays "Application active
(my_mutex_01)".

Otherwise, it displays "Application NOT active (my_mutex_01)".

Friedrich

[NewsArchive]

Hi Friedrich,

thanks for your suggestion. But your implementation is not atomic.

If I first "detect active application" and then "create named mutex", it
is possible, that between this twi statements an other instance does the
detect activ check and so I have two running instances. It is a race
condition.

If i use createmutex in kernel32.dll directly, I have an atomic
check-and-create operation.

Markus

[NewsArchive]

Hi Markus,

> If i use createmutex in kernel32.dll directly, I have an atomic
> check-and-create operation.

The "Create Named Mutex..." script function is a direct call to the
CreateMutex KERNEL32 API with the 2nd "bInitialOwner" parameter set to
FALSE.

Friedrich

[NewsArchive]

> b) It returns every time "504" or "508" as Errorcode and in the
> given variable, no matter, how many instances I run.

BTW, if it does not return 0 here then this is the expected behavior for the
CreateMutex Windows API call.

Friedrich

[NewsArchive]

Hi Friedrich,

ok, so I can use your create-mutex-function and additional check for
getlasterror?

Set Variable %MUTEX_NAME% to "AIDA SQL Client V11.21 Setup"

Call DLL "kernel32.dll" -- Function "SetLastError" (LONG) (0)

Set Variable %MUTEX% to FUNCTION:Create Named Mutex("%MUTEX_NAME%")

Call DLL "kernel32.dll" -- Function "GetLastError" () ()

Display Message Box "Ergebnis = «%_SB_RETURN%»" -- ""


Markus

[NewsArchive]

Hi Markus,

> ok, so I can use your create-mutex-function and additional check for
> getlasterror?

In your case, the only possible solution is:

Call DLL "Kernel32.dll" -- Function "CreateMutex" (*LONG,INT,STRING)
(0,0,"my_mutex_01")
Set Variable %CREATEMUTEX_ERRORCODE% to "%_SB_ERRORCODE%"
Set Variable %CREATEMUTEX_RETURN% to "%_SB_RETURN%"

Call DLL "Kernel32.dll" -- Function "GetLastError" () ()

Friedrich

[NewsArchive]

> I tried *LONG,INT,*STRING (and a few other combinations) with the

I would suggest to use: *LONG,INT,STRING

Friedrich

[NewsArchive]

Thanks, I will give it a try.

Markus