See https://github.com/thepowersgang/mrustc/archive/v0.8.0.tar.gz

--- rustc-1.19.0-src-orig/src/libcore/intrinsics.rs
+++ rustc-1.19.0-src/src/libcore/intrinsics.rs
@@ -678,5 +678,9 @@
     pub fn min_align_of_val<T: ?Sized>(_: &T) -> usize;
 
+    /// Obtain the length of a slice pointer
+    #[cfg(rust_compiler="mrustc")]
+    pub fn mrustc_slice_len<T>(pointer: *const [T]) -> usize;
+
     /// Gets a static string slice containing the name of a type.
     pub fn type_name<T: ?Sized>() -> &'static str;

--- rustc-1.19.0-src-orig/src/libcore/slice/mod.rs
+++ rustc-1.19.0-src/src/libcore/slice/mod.rs
@@ -413,6 +413,8 @@
     #[inline]
     fn len(&self) -> usize {
-        unsafe {
-            mem::transmute::<&[T], Repr<T>>(self).len
-        }
+        #[cfg(not(rust_compiler="mrustc"))]
+        let rv = unsafe { mem::transmute::<&[T], Repr<T>>(self).len };
+        #[cfg(rust_compiler="mrustc")]
+        let rv = unsafe { ::intrinsics::mrustc_slice_len(self) };
+        rv
     }
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<div class='path'>path: <a href='/guix/log/?id=080b8279be2fea11a21ac0400cb865268dd29620'>root</a>/<a href='/guix/log/etc?id=080b8279be2fea11a21ac0400cb865268dd29620'>etc</a>/<a href='/guix/log/etc/openrc?id=080b8279be2fea11a21ac0400cb865268dd29620'>openrc</a>/<a href='/guix/log/etc/openrc/guix-daemon.in?id=080b8279be2fea11a21ac0400cb865268dd29620'>guix-daemon.in</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/etc/openrc/guix-daemon.in?id=080b8279be2fea11a21ac0400cb865268dd29620&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2021-07-07 23:54:20 -0400'>2021-07-07</span></td><td><a href='/guix/commit/etc/openrc/guix-daemon.in?id=4cbe0127a668cbcc64087c5d311308b59d39b104'>guix-install.sh: Prompt for configuring substitutes discovery.</a><span class='msg-avail'>...<span class='msg-tooltip'>Also ensure prompt_yes_no always print the message with a trailing space,
which is more pleasing to the eye.

* etc/guix-daemon.conf.in &lt;--discover=no&gt;: New guix-daemon option.
* etc/guix-daemon.service.in: Likewise.
* etc/init.d/guix-daemon.in: Likewise.
* etc/openrc/guix-daemon.in: Likewise.
* etc/guix-install.sh (configure_substitute_discovery): New procedure.
(sys_enable_guix_daemon): Ask the user whether automatic substitute discovery
should be enabled.  Set the '--discover' argument accordingly.
(prompt_yes_no): Add a trailing space to the message.
(sys_authorize_build_farms): Remove trailing space from the message argument.
* NEWS (Distribution): Add news.
</span></span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2020-09-17 14:10:42 +0200'>2020-09-17</span></td><td><a href='/guix/commit/etc/openrc/guix-daemon.in?id=cabac732deffafc796537658a6c33c6c4aec821e'>guix-install.sh: Support OpenRC.</a><span class='msg-avail'>...<span class='msg-tooltip'>* etc/guix-install.sh (chk_init_sys): Detect OpenRC.
(sys_enable_guix_daemon): Install &amp; enable the Guix daemon on such
systems.
* etc/openrc/guix-daemon.in: New file.
* nix/local.mk: Add a rule for it.
(openrcservicedir, nodist_openrcservice_DATA): New variables.
(CLEANFILES, EXTRA_DIST): Add them.
* .gitignore: Ignore etc/openrc/guix-daemon.

Signed-off-by: Tobias Geerinckx-Rice &lt;me@tobias.gr&gt;
</span></span></td><td>Morgan Smith</td></tr>