feat: Use mold linker on Linux (#2304)

Fix: https://github.com/XRPLF/clio/issues/1242

Depends on: https://github.com/XRPLF/clio/pull/2329

.github/actions/generate/action.yml

@@ -29,6 +29,10 @@ inputs:
     description: Whether to enable compiler trace reports
     required: true
     default: "false"
+  use_mold:
+    description: Whether to use mold linker
+    required: true
+    default: "false"
 
 runs:
   using: composite
@@ -45,6 +49,7 @@ runs:
         STATIC_OPTION: "${{ inputs.static == 'true' && 'True' || 'False' }}"
         INTEGRATION_TESTS_OPTION: "${{ inputs.build_integration_tests == 'true' && 'True' || 'False' }}"
         TIME_TRACE: "${{ inputs.time_trace == 'true' && 'True' || 'False' }}"
+        USE_MOLD: "${{ inputs.use_mold == 'true' && 'True' || 'False' }}"
       run: |
         cd build
         conan \
@@ -58,6 +63,7 @@ runs:
           -o "&:lint=False" \
           -o "&:coverage=${CODE_COVERAGE}" \
           -o "&:time_trace=${TIME_TRACE}" \
+          -o "&:use_mold=${USE_MOLD}" \
           --profile:all "${{ inputs.conan_profile }}"
 
     - name: Run cmake
@@ -69,11 +75,13 @@ runs:
               endsWith(inputs.conan_profile, '.tsan') && '-Dsan=thread' ||
               endsWith(inputs.conan_profile, '.ubsan') && '-Dsan=undefined' ||
               '' }}
+        USE_MOLD_OPTION: "${{ inputs.use_mold == 'true' && '-DUSE_MOLD=ON' || '' }}"
       run: |
         cd build
         cmake \
           -DCMAKE_TOOLCHAIN_FILE:FILEPATH=build/generators/conan_toolchain.cmake \
           -DCMAKE_BUILD_TYPE="${BUILD_TYPE}" \
+          "${USE_MOLD_OPTION}" \
           "${SANITIZER_OPTION}" \
           .. \
           -G Ninja

.github/workflows/build_impl.yml

@@ -110,6 +110,7 @@ jobs:
           code_coverage: ${{ inputs.code_coverage }}
           static: ${{ inputs.static }}
           time_trace: ${{ inputs.analyze_build_time }}
+          use_mold: ${{ runner.os != 'macOS' }}
 
       - name: Build Clio
         uses: ./.github/actions/build_clio

CMakeLists.txt

@@ -16,6 +16,7 @@ option(lint "Run clang-tidy checks during compilation" FALSE)
 option(static "Statically linked Clio" FALSE)
 option(snapshot "Build snapshot tool" FALSE)
 option(time_trace "Build using -ftime-trace to create compiler trace reports" FALSE)
+option(use_mold "Use mold linker" FALSE)
 
 # ========================================================================== #
 set(san "" CACHE STRING "Add sanitizer instrumentation")
@@ -29,6 +30,7 @@ set(CMAKE_MODULE_PATH "${PROJECT_SOURCE_DIR}/cmake" ${CMAKE_MODULE_PATH})
 include(Ccache)
 include(CheckCXXCompilerFlag)
 include(ClangTidy)
+include(Linker)
 
 add_library(clio_options INTERFACE)
 target_compile_features(clio_options INTERFACE cxx_std_23) # Clio needs c++23 but deps can remain c++20 for now

cmake/Linker.cmake

@@ -0,0 +1,8 @@
+if (use_mold)
+  if (CMAKE_SYSTEM_NAME STREQUAL "Linux")
+    message(STATUS "Using Mold linker")
+    set(CMAKE_LINKER_TYPE MOLD)
+  else ()
+    message(FATAL_ERROR "Mold linker is only supported on Linux.")
+  endif ()
+endif ()

conanfile.py

@@ -20,7 +20,8 @@ class ClioConan(ConanFile):
         'coverage': [True, False],            # build for test coverage report; create custom target `clio_tests-ccov`
         'lint': [True, False],                # run clang-tidy checks during compilation
         'snapshot': [True, False],            # build export/import snapshot tool
-        'time_trace': [True, False]           # build using -ftime-trace to create compiler trace reports
+        'time_trace': [True, False],          # build using -ftime-trace to create compiler trace reports
+        'use_mold': [True, False],            # use mold linker for faster linking
     }
 
     requires = [
@@ -47,6 +48,7 @@ class ClioConan(ConanFile):
         'docs': False,
         'snapshot': False,
         'time_trace': False,
+        'use_mold': False,
 
         'xrpl/*:tests': False,
         'xrpl/*:rocksdb': False,