CI: Add RISC-V 64 cross-build & qemu-user tests

.github/workflows/main.yml

@@ -119,18 +119,28 @@ jobs:
             system-processor: arm
             triple: arm-linux-gnueabihf
             rtld: ld-linux-armhf.so.3
+            ld-flavour: lld
           - name: arm64
             system-processor: aarch64
             triple: aarch64-linux-gnu
             rtld: ld-linux-aarch64.so.1
+            ld-flavour: lld
           - name: ppc64el
             system-processor: powerpc64le
             triple: powerpc64le-linux-gnu
             rtld: ld64.so.2
+            ld-flavour: lld
+          - name: riscv64
+            system-processor: riscv64
+            triple: riscv64-linux-gnu
+            rtld: ld-linux-riscv64-lp64d.so.1
+            extra-packages: binutils-riscv64-linux-gnu
+            ld-flavour: bfd
+            ld: /usr/bin/riscv64-linux-gnu-ld.bfd
       # Don't abort runners if a single one fails
       fail-fast: false
     runs-on: ubuntu-latest
-    name: Cross-build for ${{ matrix.arch.triple }}
+    name: ${{matrix.build-type}} cross-build for ${{ matrix.arch.triple }}
     steps:
     - uses: actions/checkout@v2
     - name: Install cross-compile toolchain and QEMU
@@ -141,6 +151,7 @@ jobs:
         sudo add-apt-repository "deb http://apt.llvm.org/focal/     llvm-toolchain-focal-13  main"
         sudo apt update
         sudo apt install libstdc++-9-dev-${{ matrix.arch.name }}-cross qemu-user ninja-build clang-13 lld-13
+        sudo apt install ${{matrix.arch.extra-packages}}
         # The default PowerPC qemu configuration uses the wrong page size.
         # Wrap it in a script that fixes this.
         sudo update-binfmts --disable qemu-ppc64le
@@ -161,6 +172,8 @@ jobs:
         -DSNMALLOC_QEMU_WORKAROUND=ON
         -DSNMALLOC_STATIC_LIBRARY=OFF
         -DCMAKE_TOOLCHAIN_FILE=ci/Toolchain.cmake
+        -DSNMALLOC_LINKER=${{matrix.arch.ld}}
+        -DSNMALLOC_LINKER_FLAVOUR=${{matrix.arch.ld-flavour}}
     - name: Build
       working-directory: ${{github.workspace}}/build
       run: NINJA_STATUS="%p [%f:%s/%t] %o/s, %es" ninja

CMakeLists.txt

@@ -245,10 +245,21 @@ if(NOT SNMALLOC_HEADER_ONLY_LIBRARY)
     set(${result} ${dirlist} PARENT_SCOPE)
   endfunction()
 
-  set(CMAKE_REQUIRED_LINK_OPTIONS -fuse-ld=lld)
-  check_cxx_source_compiles("int main() { return 1; }" LLD_WORKS)
-  if (LLD_WORKS)
-    message(STATUS "Using LLD to link snmalloc shims")
+  if(NOT (DEFINED SNMALLOC_LINKER_FLAVOUR) OR ("${SNMALLOC_LINKER_FLAVOUR}" MATCHES "^$"))
+    # Linker not specified externally; probe to see if we can make lld work
+    set(CMAKE_REQUIRED_LINK_OPTIONS -fuse-ld=lld)
+    check_cxx_source_compiles("int main() { return 1; }" LLD_WORKS)
+    if (LLD_WORKS)
+      message(STATUS "Using LLD to link snmalloc shims")
+    endif()
+  elseif(SNMALLOC_LINKER_FLAVOUR STREQUAL "lld")
+    # Linker specified externally to be lld; assume it works and that the flags
+    # have also been set for us
+    set(LLD_WORKS TRUE)
+  else()
+    # Linker specified externally as something other than lld; presume it
+    # doesn't work and don't add its flags, below
+    set(LLD_WORKS FALSE)
   endif()
 
   function(add_shim name type)

ci/Toolchain.cmake

@@ -7,7 +7,11 @@ set(CMAKE_C_COMPILER clang-13)
 set(CMAKE_C_COMPILER_TARGET ${triple})
 set(CMAKE_CXX_COMPILER clang++-13)
 set(CMAKE_CXX_COMPILER_TARGET ${triple})
-set(CROSS_LINKER_FLAGS "-fuse-ld=lld -Wl,--dynamic-linker=/usr/${triple}/lib/$ENV{RTLD_NAME},-rpath,/usr/${triple}/lib")
+
+set(CROSS_LINKER_FLAGS "-fuse-ld=${SNMALLOC_LINKER_FLAVOUR} -Wl,--dynamic-linker=/usr/${triple}/lib/$ENV{RTLD_NAME},-rpath,/usr/${triple}/lib")
+if((DEFINED SNMALLOC_LINKER) AND NOT ("${SNMALLOC_LINKER}" MATCHES "^$"))
+  string(APPEND CROSS_LINKER_FLAGS " --ld-path=${SNMALLOC_LINKER}")
+endif()
 set(CMAKE_EXE_LINKER_FLAGS ${CROSS_LINKER_FLAGS})
 set(CMAKE_SHARED_LINKER_FLAGS ${CROSS_LINKER_FLAGS})
 set(CMAKE_MODULE_LINKER_FLAGS ${CROSS_LINKER_FLAGS})