ci: Add olddeps job to test old dependencies versions

The CI job currently just tests old Cap'n Proto versions, but it might be nice
to extend in the future to test old compilers & build tools too.

Support for versions of Cap'n Proto before 0.7.0 was dropped in
#88 in order to avoid
compiler warnings and simplify code. Before that, versions back to 0.5 were
supported and are basically still compatible since the Cap'n Proto API hasn't
changed and libmultiprocess does not rely on newer features.

Author: ryanofsky

.github/workflows/ci.yml

@@ -11,7 +11,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        config: [default, llvm, gnu32, sanitize]
+        config: [default, llvm, gnu32, sanitize, olddeps]
 
     name: build • ${{ matrix.config }}
 

ci/README.md

@@ -20,6 +20,7 @@ CI_CONFIG=ci/configs/default.bash  ci/scripts/run.sh
 CI_CONFIG=ci/configs/llvm.bash     ci/scripts/run.sh
 CI_CONFIG=ci/configs/gnu32.bash    ci/scripts/run.sh
 CI_CONFIG=ci/configs/sanitize.bash ci/scripts/run.sh
+CI_CONFIG=ci/configs/olddeps.bash  ci/scripts/run.sh
 ```
 
 By default CI jobs will reuse their build directories. `CI_CLEAN=1` can be specified to delete them before running instead.

ci/configs/olddeps.bash

@@ -0,0 +1,5 @@
+CI_DESC="CI job using old Cap'n Proto version"
+CI_DIR=build-olddeps
+export CXXFLAGS="-Werror -Wall -Wextra -Wpedantic -Wno-unused-parameter -Wno-error=array-bounds"
+NIX_ARGS=(--argstr capnprotoVersion "0.7.1")
+BUILD_ARGS=(-k)

ci/patches/spaceship.patch

@@ -0,0 +1,29 @@
+commit e3da7da967b94f373c29a198ce45f30fb9f0e517
+Author: Ed Catmur <[email protected]>
+Date:   Tue Jan 31 16:27:04 2023 +0000
+
+    Remove operator!= synthesized by spaceship
+    
+    An operator!= suppresses the reversed equality comparison candidate generation.
+    
+    This is visible in clang 16 (rc0 just released) and in gcc trunk (so probably gcc 13).
+
+diff --git a/c++/src/kj/string.h b/c++/src/kj/string.h
+index 193442aa..17835892 100644
+--- a/c++/src/kj/string.h
++++ b/c++/src/kj/string.h
+@@ -122,10 +122,14 @@ public:
+   inline constexpr const char* end() const { return content.end() - 1; }
+ 
+   inline constexpr bool operator==(decltype(nullptr)) const { return content.size() <= 1; }
++#if !__cpp_impl_three_way_comparison
+   inline constexpr bool operator!=(decltype(nullptr)) const { return content.size() > 1; }
++#endif
+ 
+   inline bool operator==(const StringPtr& other) const;
++#if !__cpp_impl_three_way_comparison
+   inline bool operator!=(const StringPtr& other) const { return !(*this == other); }
++#endif
+   inline bool operator< (const StringPtr& other) const;
+   inline bool operator> (const StringPtr& other) const { return other < *this; }
+   inline bool operator<=(const StringPtr& other) const { return !(other < *this); }

shell.nix

@@ -2,12 +2,39 @@
 , crossPkgs ? import <nixpkgs> {}
 , enableLibcxx ? false # Whether to use libc++ toolchain and libraries instead of libstdc++
 , minimal ? false # Whether to create minimal shell without extra tools (faster when cross compiling)
+, capnprotoVersion ? null
 }:
 
 let
   lib  = pkgs.lib;
   llvm = crossPkgs.llvmPackages_20;
-  capnproto = crossPkgs.capnproto.override (lib.optionalAttrs enableLibcxx { clangStdenv = llvm.libcxxStdenv; });
+  capnprotoHashes = {
+    "0.7.0" = "sha256-Y/7dUOQPDHjniuKNRw3j8dG1NI9f/aRWpf8V0WzV9k8=";
+    "0.7.1" = "sha256-3cBpVmpvCXyqPUXDp12vCFCk32ZXWpkdOliNH37UwWE=";
+    "0.8.0" = "sha256-rfiqN83begjJ9eYjtr21/tk1GJBjmeVfa3C3dZBJ93w=";
+    "0.8.1" = "sha256-OZqNVYdyszro5rIe+w6YN00g6y8U/1b8dKYc214q/2o=";
+    "0.9.0" = "sha256-yhbDcWUe6jp5PbIXzn5EoKabXiWN8lnS08hyfxUgEQ0=";
+    "0.9.2" = "sha256-BspWOPZcP5nCTvmsDE62Zutox+aY5pw42d6hpH3v4cM=";
+    "0.10.0" = "sha256-++F4l54OMTDnJ+FO3kV/Y/VLobKVRk461dopanuU3IQ=";
+    "0.10.4" = "sha256-45sxnVyyYIw9i3sbFZ1naBMoUzkpP21WarzR5crg4X8=";
+    "1.0.0" = "sha256-NLTFJdeOzqhk4ATvkc17Sh6g/junzqYBBEoXYGH/czo=";
+    "1.0.2" = "sha256-LVdkqVBTeh8JZ1McdVNtRcnFVwEJRNjt0JV2l7RkuO8=";
+    "1.1.0" = "sha256-gxkko7LFyJNlxpTS+CWOd/p9x/778/kNIXfpDGiKM2A=";
+    "1.2.0" = "sha256-aDcn4bLZGq8915/NPPQsN5Jv8FRWd8cAspkG3078psc=";
+  };
+  capnprotoBase = if capnprotoVersion == null then crossPkgs.capnproto else crossPkgs.capnproto.overrideAttrs (old: {
+    version = capnprotoVersion;
+    src = crossPkgs.fetchFromGitHub {
+      owner = "capnproto";
+      repo  = "capnproto";
+      rev   = "v${capnprotoVersion}";
+      hash  = lib.attrByPath [capnprotoVersion] "" capnprotoHashes;
+    };
+    patches = lib.optionals (lib.versionAtLeast capnprotoVersion "0.9.0" && lib.versionOlder capnprotoVersion "0.10.4") [ ./ci/patches/spaceship.patch ];
+  } // (lib.optionalAttrs (lib.versionOlder capnprotoVersion "0.10") {
+    env = { }; # Drop -std=c++20 flag forced by nixpkgs
+  }));
+  capnproto = capnprotoBase.override (lib.optionalAttrs enableLibcxx { clangStdenv = llvm.libcxxStdenv; });
   clang = if enableLibcxx then llvm.libcxxClang else llvm.clang;
   clang-tools = llvm.clang-tools.override { inherit enableLibcxx; };
 in crossPkgs.mkShell {