Merge pull request #22387 from Ericson2314/cross-3-platforms

cross stdenv: let build package's build deps resolve to native packages

1 files changed, 6 insertions, 5 deletions

diff --git a/doc/cross-compilation.xml b/doc/cross-compilation.xml
index e93d1a98f7f..32cf198449b 100644
--- a/doc/cross-compilation.xml
+++ b/doc/cross-compilation.xml
@@ -105,14 +105,15 @@
       This is the most important guiding principle behind cross-compilation with Nixpkgs, and will be called the <wordasword>sliding window principle</wordasword>.
       In this manner, given the 3 platforms for one package, we can determine the three platforms for all its transitive dependencies.
     </para>
+    <para>
+      Some examples will probably make this clearer.
+      If a package is being built with a <literal>(build, host, target)</literal> platform triple of <literal>(foo, bar, bar)</literal>, then its build-time dependencies would have a triple of <literal>(foo, foo, bar)</literal>, and <emphasis>those packages'</emphasis> build-time dependencies would have triple of <literal>(foo, foo, foo)</literal>.
+      In other words, it should take two "rounds" of following build-time dependency edges before one reaches a fixed point where, by the sliding window principle, the platform triple no longer changes.
+      Indeed, this happens with cross compilation, where only rounds of native dependencies starting with the second necessarily coincide with native packages.
+    </para>
     <note><para>
       The depending package's target platform is unconstrained by the sliding window principle, which makes sense in that one can in principle build cross compilers targeting arbitrary platforms.
     </para></note>
-    <warning><para>
-      From the above, one would surmise that if a package is being built with a <literal>(build, host, target)</literal> platform triple of <literal>(foo, bar, bar)</literal>, then its build-time dependencies would have a triple of <literal>(foo, foo, bar)</literal>, and <emphasis>those packages'</emphasis> build-time dependencies would have triple of <literal>(foo, foo, foo)</literal>.
-      In other words, it should take two "rounds" of following build-time dependency edges before one reaches a fixed point where, by the sliding window principle, the platform triple no longer changes.
-      Unfortunately, at the moment, we do <emphasis>not</emphasis> implement this correctly, and after only one round of following build-time dependencies is the fixed point reached, with target incorrectly kept different than the others.
-    </para></warning>
     <para>
       How does this work in practice? Nixpkgs is now structured so that build-time dependencies are taken from from <varname>buildPackages</varname>, whereas run-time dependencies are taken from the top level attribute set.
       For example, <varname>buildPackages.gcc</varname> should be used at build time, while <varname>gcc</varname> should be used at run time.