lib/systems/parse.nix: add, use removeAbiSuffix

gnu-config will ignore the portion of a triple matching the regex
`e?abi.*$` when determining the validity of a triple.  In other
words, `i386-linuxabichickenlips` is a valid triple.

This commit updates our parsing routines to match gnu-config.

I was recently surprised to discover that it is in fact possible to
shoehorn ABI flavors into nix doubles in a way which preserves their
property of being a (non-canonical) subset of the valid gnu-config
triples.  This commit is required in order to exploit that discovery
to add automatic detection of ILP32 platforms (64-bit void*, 32-bit
int, like the Apple Watch and MIPS n32) to Nix.

1 files changed, 10 insertions, 1 deletions

diff --git a/lib/systems/parse.nix b/lib/systems/parse.nix
index 34bfd94b3ce50..b69ad669e1874 100644
--- a/lib/systems/parse.nix
+++ b/lib/systems/parse.nix
@@ -29,6 +29,15 @@ let
       assert type.check value;
       setType type.name ({ inherit name; } // value));
 
+  # gnu-config will ignore the portion of a triple matching the
+  # regex `e?abi.*$` when determining the validity of a triple.  In
+  # other words, `i386-linuxabichickenlips` is a valid triple.
+  removeAbiSuffix = x:
+    let match = builtins.match "(.*)e?abi.*" x;
+    in if match==null
+       then x
+       else lib.elemAt match 0;
+
 in
 
 rec {
@@ -466,7 +475,7 @@ rec {
         else                     vendors.unknown;
       kernel = if hasPrefix "darwin" args.kernel      then getKernel "darwin"
                else if hasPrefix "netbsd" args.kernel then getKernel "netbsd"
-               else                                   getKernel args.kernel;
+               else                                   getKernel (removeAbiSuffix args.kernel);
       abi =
         /**/ if args ? abi       then getAbi args.abi
         else if isLinux parsed || isWindows parsed then