Add libc_bitflags convenience macro

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

1 files changed, 2 insertions, 0 deletions

diff --git a/src/lib.rs b/src/lib.rs
index f3724ec3..fc35aac3 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -19,6 +19,8 @@ extern crate cfg_if;
 #[cfg(test)]
 extern crate nix_test as nixtest;
 
+#[macro_use] mod macros;
+
 // In rust 1.8+ this should be `pub extern crate libc` but prior
 // to https://github.com/rust-lang/rust/issues/26775 being resolved
 // it is necessary to get a little creative.