This morning I spent a few hours tracking down a bug in wlroots' X11 backend. Importing a DMA-BUF via the X11 DRI3 extension failed, and I couldn't understand why.
Went from X.Org server core to Xwayland to GBM to Gallium to radeonsi to libdrm to the kernel. The FD seemed valid, since stat() didn't return an error, but drmPrimeFDToHandle failed.
So, yeah, *&%*($ to silently ignoring errors, XCB.
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