build_linux.sh: add option to choose toolchain

This adds a --toolchain CLI option to the script that can be either
  * gnu
  * llvm
  * chromium-llvm

The gnu and llvm options use the system's toolchain. chromium-llvm
uses Chromium's prebuilt LLVM toolchain.

Previously, the script tried to combine the system's gcc with
libstdc++ from Chromium's Debian sysroot, which failed to find
glibc headers:

[1/4184] CXX obj/third_party/abseil-cpp/absl/base/base/cycleclock.o
FAILED: obj/third_party/abseil-cpp/absl/base/base/cycleclock.o
g++ -MMD -MF obj/third_party/abseil-cpp/absl/base/base/cycleclock.o.d -DUSE_UDEV -DUSE_AURA=1 -DUSE_GLIB=1 -DUSE_OZONE=1 -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_LIBCPP_HARDENING_MODE=_LIBCPP_HARDENING_MODE_NONE -D_GLIBCXX_ASSERTIONS=1 -DCR_SYSROOT_KEY=20250129T203412Z-1 -DNDEBUG -DNVALGRIND -DDYNAMIC_ANNOTATIONS_ENABLED=0 -DABSL_ALLOCATOR_NOTHROW=1 -I.. -Igen -I../third_party/abseil-cpp -fno-strict-overflow -fno-ident -fno-strict-aliasing -fstack-protector -funwind-tables -fPIC -pipe -pthread -m64 -msse3 -Wno-builtin-macro-redefined -D__DATE__= -D__TIME__= -D__TIMESTAMP__= -O2 -fdata-sections -ffunction-sections -fno-math-errno -fno-omit-frame-pointer -g0 -fvisibility=hidden -Wno-unused-local-typedefs -Wno-maybe-uninitialized -Wno-deprecated-declarations -Wno-comments -Wno-packed-not-aligned -Wno-missing-field-initializers -Wno-unused-parameter -Wno-psabi -std=gnu++2a -Wno-changes-meaning -fno-exceptions --sysroot=../build/linux/debian_bullseye_amd64-sysroot -fvisibility-inlines-hidden -Wno-narrowing -Wno-class-memaccess -Wno-invalid-offsetof  -c ../third_party/abseil-cpp/absl/base/internal/cycleclock.cc -o obj/third_party/abseil-cpp/absl/base/base/cycleclock.o
In file included from /usr/include/c++/15/bits/version.h:51,
                 from /usr/include/c++/15/atomic:50,
                 from ../third_party/abseil-cpp/absl/base/internal/cycleclock.h:45,
                 from ../third_party/abseil-cpp/absl/base/internal/cycleclock.cc:23:
/usr/include/c++/15/x86_64-redhat-linux/bits/c++config.h:3:10: fatal error: bits/wordsize.h: No such file or directory
    3 | #include <bits/wordsize.h>
      |          ^~~~~~~~~~~~~~~~~

Author: Be-ing

.github/workflows/webrtc-builds.yml

@@ -47,12 +47,12 @@ jobs:
 
           - name: linux
             os: ubuntu-latest
-            cmd: ./build_linux.sh
+            cmd: ./build_linux.sh --toolchain chromium-llvm
             arch: x64
 
           - name: linux
             os: ubuntu-latest
-            cmd: ./build_linux.sh
+            cmd: ./build_linux.sh --toolchain chromium-llvm
             arch: arm64
 
           - name: android
@@ -112,36 +112,16 @@ jobs:
         run: |
          pip3 install setuptools # pkg_resources is sometimes not found?
 
-      - name: Add GCC PPA and install GCC 14
-        if: ${{ matrix.target.os == 'ubuntu-latest' }}
-        run: |
-          sudo add-apt-repository ppa:ubuntu-toolchain-r/test -y
-          sudo apt update
-          sudo apt install gcc-14 g++-14 g++-14-aarch64-linux-gnu -y
-
-      - name: Verify GCC 14 installation
-        if: ${{ matrix.target.os == 'ubuntu-latest' }}
-        run: |
-          gcc-14 --version
-          g++-14 --version
-          aarch64-linux-gnu-g++-14 --version
-
-      - name: Set GCC 14 as default (optional)
-        if: ${{ matrix.target.os == 'ubuntu-latest' }}
-        run: |
-          sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-14 140 --slave /usr/bin/g++ g++ /usr/bin/g++-14
-          sudo update-alternatives --config gcc
-          gcc --version
-          sudo update-alternatives --install /usr/bin/aarch64-linux-gnu-gcc aarch64-linux-gnu-gcc /usr/bin/aarch64-linux-gnu-gcc-14 140 --slave /usr/bin/aarch64-linux-gnu-g++ aarch64-linux-gnu-g++ /usr/bin/aarch64-linux-gnu-g++-14
-          sudo update-alternatives --config aarch64-linux-gnu-gcc
-          aarch64-linux-gnu-gcc --version
-      
       - name: Install linux dependencies
         if: ${{ matrix.target.os == 'ubuntu-latest' }}
         run: |
           sudo apt update -y
           sudo apt install -y ninja-build pkg-config openjdk-11-jdk
 
+      - name: Disable __GLIBC_USE_ISOC2X macro
+        if: ${{ matrix.target.name == 'linux' && matrix.target.arch == 'arm64' }}
+        run: sudo sed -i 's/__GLIBC_USE_ISOC2X[[:space:]]*1/__GLIBC_USE_ISOC2X\t0/' /usr/include/features.h
+
       - name: Install macos dependencies
         if: ${{ matrix.target.os == 'macos-latest' }}
         run: brew install ninja

webrtc-sys/Cargo.toml

@@ -11,12 +11,15 @@ repository = "https://github.com/livekit/client-sdk-rust"
 default = []
 
 [dependencies]
-cxx = "1.0"
+# Copy an updated version of the cxx.cc file from cxx's repository
+# into the src directory when updating to a new version of cxx
+# and change the include path for cxx.h to "rust/cxx.h"
+cxx = "=1.0.186"
 log = "0.4"
 
 [build-dependencies]
 webrtc-sys-build = { workspace = true }
-cxx-build = "1.0"
+cxx-build = "=1.0.186"
 glob = "0.3"
 cc = "1.0"
 pkg-config = "0.3.22"

webrtc-sys/build.rs

@@ -150,6 +150,23 @@ fn main() {
                 .flag("/EHsc");
         }
         "linux" => {
+            // If libwebrtc was built with Chromium's libc++, the C++ in this crate needs to be built with it too.
+            let buildtools = webrtc_include.join("buildtools/third_party/libc++");
+            if buildtools.exists() {
+                // Chromium's libc++ doesn't build with GCC
+                if env::var("CC").is_err() {
+                    builder.compiler("clang++");
+                }
+                builder.include(buildtools);
+                builder.flag("-nostdinc++");
+                let webrtc_include = webrtc_include.to_string_lossy();
+                builder.flag(format!("-isystem{webrtc_include}/third_party/libc++/src/include"));
+                builder.flag(format!("-isystem{webrtc_include}/third_party/libc++abi/src/include"));
+                // The cxx crate builds this C++ file. However, this crate needs to rebuild it when using a
+                // different C++ standard library or linking will fail with unresolved symbol errors.
+                builder.file("src/cxx.cc");
+            }
+
             println!("cargo:rustc-link-lib=dylib=rt");
             println!("cargo:rustc-link-lib=dylib=dl");
             println!("cargo:rustc-link-lib=dylib=pthread");

webrtc-sys/libwebrtc/build_linux.sh

@@ -16,6 +16,7 @@
 
 arch=""
 profile="release"
+toolchain="gnu"
 
 while [ "$#" -gt 0 ]; do
   case "$1" in
@@ -35,6 +36,14 @@ while [ "$#" -gt 0 ]; do
       fi
       shift 2
       ;;
+    --toolchain)
+      toolchain="$2"
+      if [ "$toolchain" != "gnu" ] && [ "$toolchain" != "llvm" ] && [ "$toolchain" != "chromium-llvm" ]; then
+        echo "Error: Invalid value for --toolchain. Must be 'gnu', 'llvm', or 'chromium-llvm' (Chromium's bundled Clang with Debian sysroot)"
+        exit 1
+      fi
+      shift 2
+      ;;
     *)
       echo "Error: Unknown argument '$1'"
       exit 1
@@ -50,46 +59,70 @@ fi
 echo "Building LiveKit WebRTC - Linux"
 echo "Arch: $arch"
 echo "Profile: $profile"
+echo "Toolchain: $toolchain"
+
+export COMMAND_DIR=$(cd $(dirname $0); pwd)
+export OUTPUT_DIR="$(pwd)/build-$arch-$profile"
+export ARTIFACTS_DIR="$(pwd)/linux-$arch-$profile"
+
+if [ "$toolchain" == "gnu" ]; then
+  [ -n "$CC" ] || export CC="$(which gcc)"
+  [ -n "$CXX" ] || export CXX="$(which g++)"
+  [ -n "$AR" ] || export AR="$(which ar)"
+  [ -n "$NM" ] || export NM="$(which nm)"
+  export CXXFLAGS="${CXXFLAGS} -Wno-changes-meaning -Wno-unknown-pragmas -D_DEFAULT_SOURCE"
+  OBJCOPY="$(which objcopy)"
+  chromium_libcxx=false
+  toolchain_gn_args="is_clang=false \
+  custom_toolchain=\"//build/toolchain/linux/unbundle:default\" \
+  host_toolchain=\"//build/toolchain/linux/unbundle:default\""
+elif [ "$toolchain" == "llvm" ]; then
+  [ -n "$CC" ] || export CC="$(which clang)"
+  [ -n "$CXX" ] || export CXX="$(which clang++)"
+  [ -n "$AR" ] || export AR="$(which llvm-ar)"
+  [ -n "$NM" ] || export NM="$(which llvm-nm)"
+  OBJCOPY="$(which llvm-objcopy)"
+  # Using system libc++ stumbles over
+  # https://github.com/llvm/llvm-project/issues/50248
+  # so use Chromium's libc++
+  chromium_libcxx=true
+  toolchain_gn_args="is_clang=true \
+  clang_use_chrome_plugins=false \
+  custom_toolchain=\"//build/toolchain/linux/unbundle:default\" \
+  host_toolchain=\"//build/toolchain/linux/unbundle:default\""
+elif [ "$toolchain" == "chromium-llvm" ]; then
+  AR="$COMMAND_DIR/src/third_party/llvm-build/Release+Asserts/bin/llvm-ar"
+  OBJCOPY="$COMMAND_DIR/src/third_party/llvm-build/Release+Asserts/bin/llvm-objcopy"
+  chromium_libcxx=true
+  toolchain_gn_args="is_clang=true use_custom_libcxx=true"
+fi
+
+set -x
 
 if [ ! -e "$(pwd)/depot_tools" ]
 then
   git clone --depth 1 https://chromium.googlesource.com/chromium/tools/depot_tools.git
 fi
 
-export COMMAND_DIR=$(cd $(dirname $0); pwd)
+# must be done after runing `which` to find toolchain's executables above
 export PATH="$(pwd)/depot_tools:$PATH"
-export OUTPUT_DIR="$(pwd)/src/out-$arch-$profile"
-export ARTIFACTS_DIR="$(pwd)/linux-$arch-$profile"
 
-if [ ! -e "$(pwd)/src" ]
-then
-  gclient sync -D --no-history
+if [ ! -e "$(pwd)/src" ]; then
+  # use --nohooks to avoid the download_from_google_storage hook that takes > 6 minutes
+  # then manually run the other hooks
+  gclient sync -D --no-history --nohooks
+  python3 src/tools/rust/update_rust.py
+  if [ "$toolchain" == "chromium-llvm" ] || [ "$toolchain" == "llvm" ]; then
+    python3 src/tools/clang/scripts/update.py
+  fi
 fi
 
 cd src
 git apply "$COMMAND_DIR/patches/add_licenses.patch" -v --ignore-space-change --ignore-whitespace --whitespace=nowarn
 git apply "$COMMAND_DIR/patches/ssl_verify_callback_with_native_handle.patch" -v --ignore-space-change --ignore-whitespace --whitespace=nowarn
 git apply "$COMMAND_DIR/patches/add_deps.patch" -v --ignore-space-change --ignore-whitespace --whitespace=nowarn
-
-cd build
-
-git apply "$COMMAND_DIR/patches/force_gcc.patch" -v --ignore-space-change --ignore-whitespace --whitespace=nowarn
-
-cd ..
-
-cd third_party
-
 git apply "$COMMAND_DIR/patches/david_disable_gun_source_macro.patch" -v --ignore-space-change --ignore-whitespace --whitespace=nowarn
-
-cd ../..
-
-mkdir -p "$ARTIFACTS_DIR/lib"
-
-python3 "./src/build/linux/sysroot_scripts/install-sysroot.py" --arch="$arch"
-
-if [ "$arch" = "arm64" ]; then
-  sudo sed -i 's/__GLIBC_USE_ISOC2X[[:space:]]*1/__GLIBC_USE_ISOC2X\t0/' /usr/aarch64-linux-gnu/include/features.h
-fi
+cd ..
 
 debug="false"
 if [ "$profile" = "debug" ]; then
@@ -101,10 +134,11 @@ args="is_debug=$debug  \
   target_cpu=\"$arch\" \
   rtc_enable_protobuf=false \
   treat_warnings_as_errors=false \
-  use_custom_libcxx=false \
+  use_custom_libcxx=${chromium_libcxx}
   use_llvm_libatomic=false \
   use_libcxx_modules=false \
   use_custom_libcxx_for_host=false \
+  use_sysroot=false \
   rtc_include_tests=false \
   rtc_build_tools=false \
   rtc_build_examples=false \
@@ -119,19 +153,23 @@ args="is_debug=$debug  \
   symbol_level=0 \
   enable_iterator_debugging=false \
   use_rtti=true \
-  is_clang=false \
-  rtc_use_x11=true"
+  rtc_use_x11=true \
+  $toolchain_gn_args"
+
+set -e
 
 # generate ninja files
 gn gen "$OUTPUT_DIR" --root="src" --args="${args}"
 
 # build static library
 ninja -C "$OUTPUT_DIR" :default
 
+mkdir -p "$ARTIFACTS_DIR/lib"
+
 # make libwebrtc.a
 # don't include nasm
-ar -rc "$ARTIFACTS_DIR/lib/libwebrtc.a" `find "$OUTPUT_DIR/obj" -name '*.o' -not -path "*/third_party/nasm/*"`
-objcopy --redefine-syms="$COMMAND_DIR/boringssl_prefix_symbols.txt" "$ARTIFACTS_DIR/lib/libwebrtc.a"
+"$AR" -rc "$ARTIFACTS_DIR/lib/libwebrtc.a" `find "$OUTPUT_DIR/obj" -name '*.o' -not -path "*/third_party/nasm/*"`
+"$OBJCOPY" --redefine-syms="$COMMAND_DIR/boringssl_prefix_symbols.txt" "$ARTIFACTS_DIR/lib/libwebrtc.a"
 
 python3 "./src/tools_webrtc/libs/generate_licenses.py" \
   --target :default "$OUTPUT_DIR" "$OUTPUT_DIR"
@@ -142,5 +180,11 @@ cp "$OUTPUT_DIR/args.gn" "$ARTIFACTS_DIR"
 cp "$OUTPUT_DIR/LICENSE.md" "$ARTIFACTS_DIR"
 
 cd src
+if [ $chromium_libcxx == "true" ]; then
+  mkdir -p "$ARTIFACTS_DIR/include/buildtools/third_party"
+  cp -R buildtools/third_party/libc++ "$ARTIFACTS_DIR/include/buildtools/third_party"
+  mkdir -p "$ARTIFACTS_DIR/include/third_party/libc++/src"
+  cp -R third_party/libc++/src/include "$ARTIFACTS_DIR/include/third_party/libc++/src"
+fi
 find . -name "*.h" -print | cpio -pd "$ARTIFACTS_DIR/include"
 find . -name "*.inc" -print | cpio -pd "$ARTIFACTS_DIR/include"