struct addrinfo needs padding on Solaris/SPARC

[dhduvall]

On Solaris, struct addrinfo is defined like this:

struct addrinfo {
        int ai_flags;           /* AI_PASSIVE, AI_CANONNAME, ... */
        int ai_family;          /* PF_xxx */
        int ai_socktype;        /* SOCK_xxx */
        int ai_protocol;        /* 0 or IPPROTO_xxx for IPv4 and IPv6 */
#ifdef __sparcv9
        int _ai_pad;            /* for backwards compat with old size_t */
#endif /* __sparcv9 */
        socklen_t ai_addrlen;
        char *ai_canonname;     /* canonical name for hostname */
        struct sockaddr *ai_addr;       /* binary address */
        struct addrinfo *ai_next;       /* next structure in linked list */
};

That padding member needs to be represented in Rust's copy. This is pretty straightforward, if a bit ugly. The following patch against the 1.19.0 sources fixes all the networking related test failures on SPARC:

--- rustc-1.19.0-src/src/liblibc/src/unix/solaris/mod.rs
+++ rustc-1.19.0-src/src/liblibc/src/unix/solaris/mod.rs
@@ -204,6 +204,8 @@
         pub ai_family: ::c_int,
         pub ai_socktype: ::c_int,
         pub ai_protocol: ::c_int,
+        #[cfg(target_arch = "sparc64")]
+        pub __sparcv9_pad: ::c_int,
         pub ai_addrlen: ::socklen_t,
         pub ai_canonname: *mut ::c_char,
         pub ai_addr: *mut ::sockaddr,
--- rustc-1.19.0-src/src/libstd/sys_common/net.rs
+++ rustc-1.19.0-src/src/libstd/sys_common/net.rs
@@ -165,8 +165,21 @@
     init();
 
     let c_host = CString::new(host)?;
+    #[cfg(all(target_os = "solaris", target_arch = "sparc64"))]
     let hints = c::addrinfo {
         ai_flags: 0,
+        ai_family: 0,
+        ai_socktype: c::SOCK_STREAM,
+        ai_protocol: 0,
+        __sparcv9_pad: 0,
+        ai_addrlen: 0,
+        ai_addr: ptr::null_mut(),
+        ai_canonname: ptr::null_mut(),
+        ai_next: ptr::null_mut()
+    };
+    #[cfg(not(all(target_os = "solaris", target_arch = "sparc64")))]
+    let hints = c::addrinfo {
+        ai_flags: 0,
         ai_family: 0,
         ai_socktype: c::SOCK_STREAM,
         ai_protocol: 0,

Because this is against 1.19.0, so the #[cfg] directive isn't yet allowed inside the initializer, though presumably that could be used on master, or beta with struct_field_attributes.

But I'm struggling to find an idiomatic way to do this in such a way that it needn't be mentioned in net.rs at all, and just defaulted to 0 in solaris/mod.rs, as well as a way to make it non-pub. I haven't yet tried it, but I assume I could use the Default trait. But that would still require me to add ..Default::default() to the initializer, and I would need to make the change to all the struct addrinfo definitions in libc.

Is there a better way to fix this?

[nagisa]

It is fine to use any unstable features you need in the implementation of rustc and its standard libraries. Feel free to send in a PR and r? me.

That being said the change against the structure itself will have to be PRd against https://github.com/rust-lang/libc first and only then the libstd itself changed.

[nagisa]

Something like this can be used too for the same effect:

     let hints = c::addrinfo {
         ai_socktype: c::SOCK_STREAM,
         .. mem::zeroed()
    };

[dhduvall]

Thanks, that's great! I'm not wild about having the padding member be public, but I don't see a way around that, so I submitted rust-lang/libc#714 for the libc part, and will follow up with a PR on this side shortly.

[sfackler]

I don't think it needs to be public - there are private fields in other structs in libc.

[dhduvall]

There are, but (at least for the ones in the Solaris-specific module), none of those structs are ever initialized directly, AFAICT. At least, the compiler complained at me for it not being public. I can double-check, though.

[dhduvall]

Indeed; if I remove pub from the field declaration, this is what I get when I try to compile:

error[E0451]: field `__sparcv9_pad` of struct `libc::addrinfo` is private
   --> src/libstd/sys_common/net.rs:170:12
    |
170 |         .. unsafe { mem::zeroed() }
    |            ^^^^^^^^^^^^^^^^^^^^^^^^ field `__sparcv9_pad` is private

error: aborting due to previous error

error: Could not compile `std`.

[sfackler]

You can do let mut hints = mem::zeroed(); hints.ai_socktype: c::SOCK_STREAM; instead.