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<== Date ==> | <== Thread ==> |
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Subject: | Re: BASE 7.0.x@Windows_64 - Channel Access Context in shared library - "ca_context_destroy bug" |
From: | Carsten Winkler via Tech-talk <tech-talk at aps.anl.gov> |
To: | "Johnson, Andrew N." <anj at anl.gov> |
Cc: | EPICS tech-talk <tech-talk at aps.anl.gov> |
Date: | Mon, 18 May 2020 20:24:53 +0200 |
Hi Andrew,
I am afraid that I have unknowingly used a glitch in the past. My simple example don't work for any EPICS Base version. But up to EPICS Base 3.14.12.8 I could unload the library by using the destructor function of a static object in my interface library.
After compiling CA Lab with EPICS Base 7, LabVIEW now freezes completely when you close a VI with CA Lab modules. This problem is new and very critical.
Hi Carsten,
I’m not aware of anything that has actually been added to libCom or libca recently to prevent a completely shutdown; are you saying that you used to be able to unload the CA library and you can’t now? I don’t believe this has ever been possible (which is probably what Michael is also going by), but I might be wrong – please let us know what version of Base you were using if and when you could do that.
If it’s your requirement that has changed we would be happy to advise someone how to work out what needs to be modified to allow the complete unloading that you’re looking for, but I can’t promise that we’ll have core developer effort available to do the actual investigation and any development needed (we all manage our own time and have our own priorities controlled by our employers, so I can’t speak for the others).
- Andrew
On May 18, 2020, at 12:21 PM, Carsten Winkler via Tech-talk <tech-talk at aps.anl.gov> wrote:
thank you for your answer. This are bad news for our community. Many users are waiting for an EPICS Base upgrade for the Open Source software CaLab (interface beween LabVIEW and EPICS).
Best reganrds
Carsten
Am 18.05.2020 um 18:27 schrieb Michael Davidsaver:
libca and especially libCom can't be completely shutdown, and therefore can't be safely unloaded. On 5/18/20 8:34 AM, Carsten Winkler via Tech-talk wrote:Hi, for a project I need to load and unload the Channel Access context in a shared library. Loading is no problem but unloading. It always fails during ca_context_destroy() function. Here is my demo code: main.cpp (most simple case for a bigger project where it's necessary to load and unload different shared libraries at runtime without terminating main application) ---------------------------------------------------------- #include <windows.h> #include <iostream> int main() { HINSTANCE hinstLib; BOOL fFreeResult; hinstLib = LoadLibrary(TEXT("myCaLib.dll")); if (hinstLib == NULL) { std::cout << "myCaLib.dll not found" << std::endl; return 1; } std::cout << "library loaded; hit ENTER to unload" << std::endl; getchar(); fFreeResult = FreeLibrary(hinstLib); std::cout << "bye" << std::endl; return 0; } _______________________________________________________________________ myCaLib.cpp (most simple shared library with no functions except creating and releasing the Channel Access context) -------------------------------------------------------------- #include <iostream> #include <cadef.h> #include <windows.h> BOOLEAN WINAPI DllMain(HINSTANCE hDllHandle, DWORD nReason, LPVOID Reserved) { switch (nReason) { case DLL_PROCESS_ATTACH: { int32_t iResult = ca_context_create(ca_enable_preemptive_callback); if (iResult != ECA_NORMAL) { std::cout << "Error: Could not create any instance of Channel Access." << std::endl; return 0; } std::cout << "New instance of Channel Access context." << std::endl; std::cout << ca_context_status(ca_current_context(), 1) << std::endl; break; } case DLL_PROCESS_DETACH: { std::cout << "detach process ... " << std::endl; ca_context_destroy(); break; } } return 1; } _______________________________________________________________________ build at command line at Windows 7 64 bit -------------------------------------------------------------- %comspec% /k "C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Auxiliary\Build\vcvars64.bat" set base=C:\base-7.0.x <== directory of nightly build or stable EPICS BASE 7.0 (built with "EPICS_HOST_ARCH=windows-x64") cd C:\test_case\ <== directory of our test sources main.cpp and myCaLib.cpp cl -nologo -FC -D__STDC__=0 -D_CRT_SECURE_NO_DEPRECATE -D_CRT_NONSTDC_NO_DEPRECATE -Ox -GL -Oy- -W3 -MD -EHsc -DEPICS_BUILD_DLL -DEPICS_CALL_DLL -I%base%/include/compiler/msvc -I%base%/include/os/WIN32 -I%base%/include -c main.cpp myCaLib.cpp link -nologo -subsystem:windows -dll -LTCG -incremental:no -opt:ref -release -version:7.0 -MACHINE:X64 -libpath:%base%\lib\windows-x64 -out:myCaLib.dll -implib:myCaLib.lib myCaLib.obj ca.lib Com.lib link -nologo -LTCG -incremental:no -opt:ref -release -version:7.0 -MACHINE:X64 -out:test.exe main.obj set path=%base%\bin\windows-x64;%path% test.exe _______________________________________________________________________ test.exe will freeze because it hangs on ca_context_destroy() I need any solution for this case, please. Best regards Carsten ________________________________ Helmholtz-Zentrum Berlin für Materialien und Energie GmbH Mitglied der Hermann von Helmholtz-Gemeinschaft Deutscher Forschungszentren e.V. Aufsichtsrat: Vorsitzender Dr. Volkmar Dietz, stv. Vorsitzende Dr. Jutta Koch-Unterseher Geschäftsführung: Prof. Dr. Bernd Rech (Sprecher), Prof. Dr. Jan Lüning, Thomas Frederking Sitz Berlin, AG Charlottenburg, 89 HRB 5583 Postadresse: Hahn-Meitner-Platz 1 D-14109 Berlin
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH
Mitglied der Hermann von Helmholtz-Gemeinschaft Deutscher Forschungszentren e.V.
Aufsichtsrat: Vorsitzender Dr. Volkmar Dietz, stv. Vorsitzende Dr. Jutta Koch-Unterseher
Geschäftsführung: Prof. Dr. Bernd Rech (Sprecher), Prof. Dr. Jan Lüning, Thomas Frederking
Sitz Berlin, AG Charlottenburg, 89 HRB 5583
Postadresse:
Hahn-Meitner-Platz 1
D-14109 Berlin
--Complexity comes for free, simplicity you have to work for.