mpgen: Work around c++20 / capnproto 0.8 incompatibility

.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 }}
 

CMakeLists.txt

@@ -12,8 +12,29 @@ endif()
 
 include("cmake/compat_find.cmake")
 
-find_package(CapnProto 0.7.0 REQUIRED)
 find_package(Threads REQUIRED)
+find_package(CapnProto 0.7 REQUIRED)
+
+# Check for list-of-pointers memory access bug from Nov 2022
+# https://nvd.nist.gov/vuln/detail/CVE-2022-46149
+# https://github.com/advisories/GHSA-qqff-4vw4-f6hx
+# https://github.com/capnproto/capnproto/security/advisories/GHSA-qqff-4vw4-f6hx
+# https://github.com/capnproto/capnproto/blob/master/security-advisories/2022-11-30-0-pointer-list-bounds.md
+# https://capnproto.org/news/2022-11-30-CVE-2022-46149-security-advisory.html
+# https://dwrensha.github.io/capnproto-rust/2022/11/30/out_of_bounds_memory_access_bug.html
+if(CapnProto_VERSION STREQUAL "0.7.0"
+   OR CapnProto_VERSION STREQUAL "0.8.0"
+   OR CapnProto_VERSION STREQUAL "0.9.0"
+   OR CapnProto_VERSION STREQUAL "0.9.1"
+   OR CapnProto_VERSION STREQUAL "0.10.0"
+   OR CapnProto_VERSION STREQUAL "0.10.1"
+   OR CapnProto_VERSION STREQUAL "0.10.2")
+  message(FATAL_ERROR
+    "Cap'n Proto ${CapnProto_VERSION} is affected by CVE-2022-46149.\n"
+    "Please install an updated package.\n"
+    "Details: https://github.com/advisories/GHSA-qqff-4vw4-f6hx
+  ")
+endif()
 
 set(MPGEN_EXECUTABLE "" CACHE FILEPATH "If specified, should be full path to an external mpgen binary to use rather than the one built internally.")
 

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); }

doc/install.md

@@ -1,6 +1,6 @@
 # libmultiprocess Installation
 
-Installation currently requires Cap'n Proto:
+Installation currently requires Cap'n Proto 0.7 or higher:
 
 ```sh
 apt install libcapnp-dev capnproto

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 {

src/mp/gen.cpp

@@ -146,7 +146,7 @@ static void Generate(kj::StringPtr src_prefix,
     const std::vector<kj::Own<const kj::ReadableDirectory>>& import_dirs)
 {
     std::string output_path;
-    if (src_prefix == ".") {
+    if (src_prefix == kj::StringPtr{"."}) {
         output_path = src_file;
     } else if (!src_file.startsWith(src_prefix) || src_file.size() <= src_prefix.size() ||
                src_file[src_prefix.size()] != '/') {
@@ -156,7 +156,7 @@ static void Generate(kj::StringPtr src_prefix,
     }
 
     std::string include_path;
-    if (include_prefix == ".") {
+    if (include_prefix == kj::StringPtr{"."}) {
         include_path = src_file;
     } else if (!src_file.startsWith(include_prefix) || src_file.size() <= include_prefix.size() ||
                src_file[include_prefix.size()] != '/') {
@@ -425,8 +425,8 @@ static void Generate(kj::StringPtr src_prefix,
 
                 const std::string method_prefix = Format() << message_namespace << "::" << method_interface.getShortDisplayName()
                                                            << "::" << Cap(method_name);
-                const bool is_construct = method_name == "construct";
-                const bool is_destroy = method_name == "destroy";
+                const bool is_construct = method_name == kj::StringPtr{"construct"};
+                const bool is_destroy = method_name == kj::StringPtr{"destroy"};
 
                 struct Field
                 {
@@ -465,7 +465,7 @@ static void Generate(kj::StringPtr src_prefix,
                         field.result_is_set = true;
                     }
 
-                    if (!param && field_name == "result") {
+                    if (!param && field_name == kj::StringPtr{"result"}) {
                         field.retval = true;
                         has_result = true;
                     }