From ba497e62f29b10ad83cb4467fbbaff155ec89c99 Mon Sep 17 00:00:00 2001
From: anrp <anrp@tri.global>
Date: Fri, 2 Jun 2023 05:53:05 -0400
Subject: [PATCH] Force Unreal toolchain to use Unreal sysroot

Not doing this can lead to the Unreal toolchain examining the host system,
which can cause it to attempt to use glibc features newer than the Unreal
target of 2.17 provides (specifically, rpclib can accidentaly pick up the
symbol pthread_cond_clockwait, which is provided by Ubuntu 20.04 glibc 2.31
but *not* by Unreal glibc 2.17, which then causes a missing symbol linker
error when trying to build CARLA. The reason is that libc++ attempts to
detect glibc version in its headers and conditionally uses that symbol.)
---
 Util/BuildTools/Setup.sh | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/Util/BuildTools/Setup.sh b/Util/BuildTools/Setup.sh
index 42147adbc..2859edd3c 100755
--- a/Util/BuildTools/Setup.sh
+++ b/Util/BuildTools/Setup.sh
@@ -57,6 +57,7 @@ pushd ${CARLA_BUILD_FOLDER} >/dev/null
 
 LLVM_INCLUDE="$UE4_ROOT/Engine/Source/ThirdParty/Linux/LibCxx/include/c++/v1"
 LLVM_LIBPATH="$UE4_ROOT/Engine/Source/ThirdParty/Linux/LibCxx/lib/Linux/x86_64-unknown-linux-gnu"
+UNREAL_HOSTED_CFLAGS="--sysroot=$UE4_ROOT/Engine/Extras/ThirdPartyNotUE/SDKs/HostLinux/Linux_x64/v17_clang-10.0.1-centos7/x86_64-unknown-linux-gnu/"
 
 # ==============================================================================
 # -- Get boost includes --------------------------------------------------------
@@ -173,7 +174,7 @@ else
   pushd ${RPCLIB_BASENAME}-libcxx-build >/dev/null
 
   cmake -G "Ninja" \
-      -DCMAKE_CXX_FLAGS="-fPIC -std=c++14 -stdlib=libc++ -I${LLVM_INCLUDE} -Wl,-L${LLVM_LIBPATH} -DBOOST_NO_EXCEPTIONS -DASIO_NO_EXCEPTIONS" \
+      -DCMAKE_CXX_FLAGS="-fPIC -std=c++14 -stdlib=libc++ -I${LLVM_INCLUDE} -Wl,-L${LLVM_LIBPATH} -DBOOST_NO_EXCEPTIONS -DASIO_NO_EXCEPTIONS ${UNREAL_HOSTED_CFLAGS}" \
       -DCMAKE_INSTALL_PREFIX="../${RPCLIB_BASENAME}-libcxx-install" \
       ../${RPCLIB_BASENAME}-source
 
@@ -237,7 +238,7 @@ else
   pushd ${GTEST_BASENAME}-libcxx-build >/dev/null
 
   cmake -G "Ninja" \
-      -DCMAKE_CXX_FLAGS="-std=c++14 -stdlib=libc++ -I${LLVM_INCLUDE} -Wl,-L${LLVM_LIBPATH} -DBOOST_NO_EXCEPTIONS -fno-exceptions" \
+      -DCMAKE_CXX_FLAGS="-std=c++14 -stdlib=libc++ -I${LLVM_INCLUDE} -Wl,-L${LLVM_LIBPATH} -DBOOST_NO_EXCEPTIONS -fno-exceptions ${UNREAL_HOSTED_CFLAGS}" \
       -DCMAKE_INSTALL_PREFIX="../${GTEST_BASENAME}-libcxx-install" \
       ../${GTEST_BASENAME}-source
 
@@ -530,7 +531,7 @@ if ${USE_CHRONO} ; then
     pushd ${CHRONO_SRC_DIR}/build >/dev/null
 
     cmake -G "Ninja" \
-        -DCMAKE_CXX_FLAGS="-fPIC -std=c++14 -stdlib=libc++ -I${LLVM_INCLUDE} -L${LLVM_LIBPATH} -Wno-unused-command-line-argument" \
+        -DCMAKE_CXX_FLAGS="-fPIC -std=c++14 -stdlib=libc++ -I${LLVM_INCLUDE} -L${LLVM_LIBPATH} -Wno-unused-command-line-argument ${UNREAL_HOSTED_CFLAGS}" \
         -DEIGEN3_INCLUDE_DIR="../../${EIGEN_INCLUDE}" \
         -DCMAKE_INSTALL_PREFIX="../../${CHRONO_INSTALL_DIR}" \
         -DCMAKE_BUILD_TYPE=Release \
@@ -840,9 +841,9 @@ cp ${LIBSTDCPP_TOOLCHAIN_FILE}.gen ${LIBCPP_TOOLCHAIN_FILE}.gen
 cat >>${LIBCPP_TOOLCHAIN_FILE}.gen <<EOL
 
 set(CMAKE_CXX_FLAGS "\${CMAKE_CXX_FLAGS} -stdlib=libc++" CACHE STRING "" FORCE)
-set(CMAKE_CXX_FLAGS "\${CMAKE_CXX_FLAGS} -isystem ${LLVM_INCLUDE}" CACHE STRING "" FORCE)
+set(CMAKE_CXX_FLAGS "\${CMAKE_CXX_FLAGS} -isystem ${LLVM_INCLUDE} ${UNREAL_HOSTED_CFLAGS}" CACHE STRING "" FORCE)
 set(CMAKE_CXX_FLAGS "\${CMAKE_CXX_FLAGS} -fno-exceptions" CACHE STRING "" FORCE)
-set(CMAKE_CXX_LINK_FLAGS "\${CMAKE_CXX_LINK_FLAGS} -L${LLVM_LIBPATH}" CACHE STRING "" FORCE)
+set(CMAKE_CXX_LINK_FLAGS "\${CMAKE_CXX_LINK_FLAGS} -L${LLVM_LIBPATH} ${UNREAL_HOSTED_CFLAGS}" CACHE STRING "" FORCE)
 set(CMAKE_CXX_LINK_FLAGS "\${CMAKE_CXX_LINK_FLAGS} -lc++ -lc++abi" CACHE STRING "" FORCE)
 EOL