build failures on some architectures

[alexanderkjall]

Is this crate only meant to be used on some architectures?

Example of error output (from here: https://ci.debian.net/packages/r/rust-capctl/testing/i386/66184398/ ):

 83s error[E0433]: failed to resolve: could not find `syscall` in `sc`
 83s   --> src/caps/capstate.rs:61:25
 83s    |
 83s 61 |                     sc::syscall!(CAPGET, &mut header as *mut _, raw_dat.as_mut_ptr())
 83s    |                         ^^^^^^^ could not find `syscall` in `sc`
 83s 
 83s error[E0433]: failed to resolve: could not find `syscall` in `sc`
 83s    --> src/caps/capstate.rs:104:25
 83s     |
 83s 104 |                     sc::syscall!(CAPSET, &mut header as *mut _, raw_dat.as_ptr())
 83s     |                         ^^^^^^^ could not find `syscall` in `sc`
 83s 
 83s error[E0433]: failed to resolve: could not find `syscall` in `sc`
 83s   --> src/caps/helpers.rs:67:46
 83s    |
 83s 67 |                     crate::sc_res_decode(sc::syscall!(SETRESUID32, ruid, euid, suid))?;
 83s    |                                              ^^^^^^^ could not find `syscall` in `sc`
 83s 
 83s error[E0433]: failed to resolve: could not find `syscall` in `sc`
 83s   --> src/caps/helpers.rs:82:46
 83s    |
 83s 82 |                     crate::sc_res_decode(sc::syscall!(SETRESGID32, rgid, egid, sgid))?;
 83s    |                                              ^^^^^^^ could not find `syscall` in `sc`
 83s 
 83s error[E0433]: failed to resolve: could not find `syscall` in `sc`
 83s   --> src/caps/helpers.rs:97:46
 83s    |
 83s 97 |                     crate::sc_res_decode(sc::syscall!(SETGROUPS32, size, list))?;
 83s    |                                              ^^^^^^^ could not find `syscall` in `sc`
 83s 
 83s error[E0433]: failed to resolve: could not find `syscall` in `sc`
 83s    --> src/prctl.rs:343:21
 83s     |
 83s 343 |                 sc::syscall!(PRCTL, libc::PR_GET_TIMERSLACK, 0, 0, 0)
 83s     |                     ^^^^^^^ could not find `syscall` in `sc`
 83s 
 83s error[E0433]: failed to resolve: could not find `syscall` in `sc`
 83s   --> src/lib.rs:75:38
 83s    |
 83s 75 |             return sc_res_decode(sc::syscall!(PRCTL, option, arg2, arg3, arg4, arg5))
 83s    |                                      ^^^^^^^ could not find `syscall` in `sc`
 83s 
 83s error[E0433]: failed to resolve: could not find `syscall` in `sc`
 83s   --> src/lib.rs:99:27
 83s    |
 83s 99 |             let res = sc::syscall!(PRCTL, option, arg2, arg3, arg4, arg5);
 83s    |                           ^^^^^^^ could not find `syscall` in `sc`

it seems to fail on:
i386, ppc64el and s390x

as can be seen here: https://qa.debian.org/excuses.php?package=rust-capctl

[cptpcrd]

The build job you linked to is failing because it enables the optional sc feature, which uses the sc crate to make raw syscalls with inline assembly. The sc crate has limited architecture support, which this crate inherits when the sc feature is specified.

I'll probably do something about this for the next release (perhaps only have the feature take effect on common architectures)? In the meantime, if you want this crate to compile on architectures not supported by sc, simply don't enable the sc feasture.