Commits on Jun 20, 2023

1. treewide: expunge functions from platforms …

   This commit moves `canExecute`, `emulator`, and `emulatorAvailable`
   out of `{host,build,target}Platform` and lifts them into
   `lib.systems`.  Stubs have been left behind to assist with migration
   of out-of-tree code.
   
   Nix's function equality is unpredictable and error-prone; we should
   not rely on it.  Since we need to be able to test
   `{host,build,target}Platform` attrsets for equality, the most
   sustainable long-term solution is to forbid functions from these
   attrsets, much like we do for the `meta` attrset.
   
   The stubs which have been left behind are a narrowly-defined case
   where Nix's function equality *does* behave predictably.

   Adam Joseph committed Jun 20, 2023
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2. lib.systems.elaborate: make placeholder functions always identical …

   Comparing platform sets using `==` works for most cases since the in the
   native case, the platform sets would not only be equal, but the same
   identical value (in terms of memory location). This is, however,
   technically not always the case, e.g. when specifying crossSystem
   explicitly, cases can arise when we should use a native stdenv, but
   don't since the functions wouldn't compare as equal due to them being
   constructed in separate invocations of `lib.system.elaborate`. This
   problem is described in #237427 and motivated #237512 as an equality
   predicate that ignors the functions.
   
   Since the functions in the platform attribute set no longer relate to
   the platform set at all, we can use the same function value for every
   placeholder deprecation error function in the attribute set—consequently
   they will all compare as equal even for independently constructed
   platform sets.
   
   This is achieved by floating the funtions into a let binding in
   `lib/systems/default.nix`, ensuring that they are only constructed once
   per nixpkgs instance, i.e. when that file is imported. (Consequently,
   comparison of platform sets should be reliable as long as they come from
   the same instance of nixpkgs.)
   
       let
         inherit (
           import <nixpkgs> {
             localSystem = "x86_64-linux";
             crossSystem.system = "x86_64-linux";
           }
         ) buildPlatform
           hostPlatform
           ;
       in
   
       buildPlatform == hostPlatform
       # => true
   
   This property is also verified with new test cases.

   

   sternenseemann authored and Adam Joseph committed Jun 20, 2023
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3. gcc12: disable libsanitizer for mips64 …

       Without the change build on mips64-unknown-linux-gnu fails as:
   
           $ nix-build -A buildPackages.gcc12 --argstr crossSystem mips64-linux
   
           In file included from ...-glibc-mips64-unknown-linux-gnu-2.37-8-dev/include/bits/stat.h:25,
                            from ...-glibc-mips64-unknown-linux-gnu-2.37-8-dev/include/fcntl.h:78,
                            from ../../../../gcc-12.3.0/libsanitizer/sanitizer_common/sanitizer_linux.cpp:55:
           ...-glibc-mips64-unknown-linux-gnu-2.37-8-dev/include/bits/struct_stat.h:190:8: error: redefinition of 'struct stat64'
             190 | struct stat64
                 |        ^~~~~~

   

   trofi authored and Adam Joseph committed Jun 20, 2023
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