Type discrepancy for permissions

[sector-f]

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The chmod function passes the mode as a u32, but the perm field of FileAttr is a u16

[wfraser]

This is because FUSE passes the mode as a u32, which is because the mode_t in chmod(2) is actually a 32-bit integer on some platforms (Linux at least). Not all the bits have a well-defined meaning, which is why FileAttr only takes a u16, but I guess nothing stops you from doing chmod(path, 0x10000); on Linux.

[wfraser]

So I did some experiments, and found something interesting. On Linux, while you can pass any 32-bit value to chmod(), at some level it gets a mask applied and the maximum value fuse_mt sees is 0x8FFF. I'm not sure if this is the kernel or FUSE doing this.

So it might make sense to change the type after all.

[wfraser]

Looks like macOS does the same thing; even though it defines mode_t as unsigned short (16 bits), everything is masked to 0x8FFF.