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We define many bitflags types with values from the libc crate. Currently
these look like this:
bitflags!{
flags ProtFlags: libc::c_int {
const PROT_NONE = libc::PROT_NONE,
const PROT_READ = libc::PROT_READ,
const PROT_WRITE = libc::PROT_WRITE,
const PROT_EXEC = libc::PROT_EXEC,
#[cfg(any(target_os = "linux", target_os = "android"))]
const PROT_GROWSDOWN = libc::PROT_GROWSDOWN,
#[cfg(any(target_os = "linux", target_os = "android"))]
const PROT_GROWSUP = libc::PROT_GROWSUP,
}
}
There's some repetition which is tedious. With the new macro, the above
can instead be written
libc_bitflags!{
flags ProtFlags: libc::c_int {
PROT_NONE,
PROT_READ,
PROT_WRITE,
PROT_EXEC,
#[cfg(any(target_os = "linux", target_os = "android"))]
PROT_GROWSDOWN,
#[cfg(any(target_os = "linux", target_os = "android"))]
PROT_GROWSUP,
}
}
Thanks to Daniel Keep for the Little Book of Rust Macros, and for
helping with this macro.
Refs https://github.com/nix-rust/nix/issues/264
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