I found the root cause of this problem.
I statically linked libusb-1.0 to my main program.
And I also statically linked libusb-1.0 into a DLL library.
In my main program, I opened a device and in the DLL library, I used
libusb_control_transfer to work on the device.
Because of static link, there are some static variables in windows_usb.c has
different copies in both main program and DLL library.
In main program I called libusb_init, this call only initialize the
libusb_context structure in main program, but in the DLL library, libusb_init
is not called, therefore, the FD inside the libusb_context of the DLL library
remains un-initialized.
Solution: dynamically link the program, everything is fixed.
Second solution: windows_usb.c should put the static global variable into
libusb_context, in this case, only one libusb_context instance will be used
between different library.
---
Reply to this email directly or view it on GitHub:
https://github.com/libusbx/libusbx/issues/165#issuecomment-30866375
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