Re: Building cargo-c on netbsd-10/i386 fails

[Havard Eidnes <he%NetBSD.org@localhost>]

> Attempting to build "devel/cargo-c" from pkgsrc-HEAD on up-to-date
> NetBSD/i386-10.0_BETA fails with:
>
> [...]
> ===> Building for cargo-c-0.9.24
>    Compiling faster-hex v0.8.0
> error[E0425]: cannot find function `vectorization_support_no_cache_x86` in this scope
>   --> /tmp/pkgsrc/devel/cargo-c/work/vendor/faster-hex-0.8.0/src/lib.rs:63:28
>    |
> 63 |         let val = unsafe { vectorization_support_no_cache_x86() };
>    |                            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not found in this scope
>
> For more information about this error, try `rustc --explain E0425`.
> error: could not compile `faster-hex` (lib) due to previous error
> *** Error code 101

Hmm...  I suspect this has something to do with which particular
i386 CPU variant we build rust for, and that we've made an
"unusual" choice...

Looking at the code, in work/vendor/faster-hex-0.8.0/src/lib.rs
reveals that the use of vectorization_support_no_cache_x86() is
conditional on

    #[cfg(all(any(target_arch = "x86", target_arch = "x86_64")))]

whereas the function definition just below is conditional on

#[target_feature(enable = "xsave")]
#[cfg(all(
    any(target_arch = "x86", target_arch = "x86_64"),
    target_feature = "sse"
))]
#[cold]

Our rust is built for the i486--netbsdelf GNU target (for maximal
CPU support), and that might mean that our rust doesn't support
the "sse" target feature.  This means that for our i386 rust this
function ends up as "used but not defined".  Arguably this is a
bug in the faster-hex cargo crate.

I've locally added this patch:

$NetBSD$

Unify conditions for vectorization_support() use and definition.

--- ../vendor/faster-hex-0.8.0/src/lib.rs.orig  2006-07-24 01:21:28.000000000 +0000
+++ ../vendor/faster-hex-0.8.0/src/lib.rs
@@ -43,7 +43,8 @@ pub(crate) enum Vectorization {
 
 #[inline(always)]
 pub(crate) fn vectorization_support() -> Vectorization {
-    #[cfg(all(any(target_arch = "x86", target_arch = "x86_64")))]
+    #[cfg(all(any(target_arch = "x86", target_arch = "x86_64"),
+              target_feature = "sse"))]
     {
         use core::sync::atomic::{AtomicU8, Ordering};
         static FLAGS: AtomicU8 = AtomicU8::new(u8::MAX);

And with this in place the build at least got past the faster-hex
crate build:

...
   Compiling gix-url v0.19.0
   Compiling faster-hex v0.8.0
   Compiling regex v1.9.4
...

on NetBSD/i386 8.2 with rust 1.71.1 (from wip).

Luckily, it doesn't look like I need to patch any cargo
checksums, so I'll commit this patch shortly (I'll let the
cargo-c build complete first).

Regards,

- Håvard