How can I know dll file path in C++ API Control Extension

[kiducduc]

Hello.

When I make API Control Extension (dll) ref. with another dll (c++),

put them in same folder (WinCC_OA_Proj\\bin\\) and call API function in API Control Extension, then dll can't find referenced dll.

But, put referenced dll in system32 folder, then API Control Extension works well.

That is,
WinCC OA Project -> WinCC_OA_Proj
API Control Extension -> MyCtrlExt.dll
referenced dll -> ref.dll
file location -> D:\\WinCC_OA_Proj\\bin\\
message -> missing ref.dll

So, my question is:

1. how can get actual file path of API Control Extension path (in above case, I want get "D:\\WinCC_OA_Proj\\bin\\MyCtrlExt.dll")

2. or how can use API Control Extension with another dll in same folder.

[Gertjan van Schijndel]

1a) In CTRL: getPath(BIN_REL_PATH, "MyCtrlExt.dll")
1b) In C++ API: PVSSFileSys::fileExists(Resources::getProjBinDir, "MyCtrlExt.dll")
1) How does knowing the actual path of the control extension help you?

2) The system32 directory is included in the 'PATH' environment variable, that is why it works if the referenced dll is there. So adding the drectory containing the referenced dll to the 'PATH' variable, before the control extension is loaded, should work.
In case the referenced dll is delay-loaded or dynamically loaded also the control extension itself could modify the 'PATH' variable before the referenced dll is actually loaded.

[kiducduc]

Gertjan van Schijndel wrote:

1a) In CTRL: getPath(BIN_REL_PATH, "MyCtrlExt.dll")
1b) In C++ API: PVSSFileSys::fileExists(Resources::getProjBinDir, "MyCtrlExt.dll")
1) How does knowing the actual path of the control extension help you?

With actual path, I was trying to use "LoadLibrary" function to import dll or register environment variable.

So, the way of 1b) works perfect in my dll.

Thank you.

[mberdich]

Hi Gertjan, Hi Jon Gyun
we need help:
- how could we add the dll path to the PATH variable via ctrl ext?
- do you have an example for us?

thanks a lot!

[Gertjan van Schijndel]

In C++ API an environment variable can be set with 'NoPosix::setenv'. Setting the PATH environment variable only helps if the control extension is actually loaded, so it does not help to resolve finding statically linked libraries.

[mberdich]

Hi Gertjan,
I tried following:
1) Add /DELAYLOAD:"test.dll" to the compiler.
2) In the ctrl extension execute function i add the absolute path of the dll
tot he PATH variable
3) Now the ui does not crash while starting the ui manager but if i execute
the function where the external dll is used the ui manager crashes without a
message

What do i wrong?

best regards,
mario

[Gertjan van Schijndel]

Perhaps the path must be set before the control extension (dll) is loaded also in case of delayed loading.

But normally if a control extension is tried to load, which is missing dependencies, the UI does not crash. Only a 'version is not compatible' error is thrown. Maybe there is something else wrong in your control extension, causing the crash.

[CyaNn]

Personnaly, I use some good old C++ windows tools to find my linkage errors :
- sysinternal dependency walker
- sysinternals listdlls

all are available here :
https://docs.microsoft.com/en-us/sysint ... downloads/

also another usefull tool : WinDbg

I hope it help