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gphoto / libgphoto2

The libgphoto2 camera access and control library.
GNU Lesser General Public License v2.1
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Cannot open session to Canon with v2.5.28 (Windows build) #814

Closed manongjohn closed 2 years ago

manongjohn commented 2 years ago

Describe the bug

I know Windows builds aren't really supported but I have built a Win64 version of libgphoto2 using MSVC 2019 and integrated into my application. I can normally connect and control my camera with v2.5.27, but cannot connect to the camera when I use v2.5.28 or later.

I've narrowed the issue to commit b6fae4fcceb3d3352bf24728045293d694a3e835. I verified I could still connect/control my camera with the commit just before this one, but breaks when this commit is present.

Here are excerpts of my application logs with GP_LOG_ALL enabled as it tries to open sessions: v2.5.27-working.txt v2.5.28-broken.txt

Doesn't appear to be writing the correct amount of bytes to the camera after this change? Was working when it was writing 16 bytes but with this commit it appears to only be writing 12 bytes to the camera.

I can provide more information if desired. Hopefully someone can help with this problem.

Name the camera Camera recognized as Canon EOS 1500D. I had to change it's normal USB driver to libusbK (v3.1.0.0) in order to be able to control my camera with libgphoto2.

libgphoto2 and gphoto2 version libgphoto2 v.2.5.28 and later

manongjohn commented 2 years ago

Nevermind. After some research, I found out I was a missing option when compiling in MSCV so it was not handling __VA_ARGS__ correctly. I had to make sure I had /Zc:preprocessor compiler switch enabled.

ndim commented 2 years ago

Hmm. I would prefer if the compile failed instead of producing buggy executable code. Let me keep this open to see what I have broken here.

https://docs.microsoft.com/en-us/cpp/build/reference/zc-preprocessor?view=msvc-170 might be helpful.