From 21c24ae9029a1fcd1c76b61b1c48b81b5c66c606 Mon Sep 17 00:00:00 2001
From: Louis Dionne <ldionne.2@gmail.com>
Date: Tue, 15 Jun 2021 18:47:38 -0400
Subject: [PATCH] [runtimes] Always build libc++, libc++abi and libunwind with
 -fPIC

Building the libraries with -fPIC ensures that we can link an executable
against the static libraries with -fPIE. Furthermore, there is apparently
basically no downside to building the libraries with position independent
code, since modern toolchains are sufficiently clever.

This commit enforces that we always build the runtime libraries with -fPIC.
This is another take on D104327, which instead makes the decision of whether
to build with -fPIC or not to the build script that drives the runtimes'
build.

Fixes http://llvm.org/PR43604.

Differential Revision: https://reviews.llvm.org/D104328
---
 libcxx/src/CMakeLists.txt    | 2 ++
 libcxxabi/src/CMakeLists.txt | 2 ++
 libunwind/src/CMakeLists.txt | 2 ++
 3 files changed, 6 insertions(+)

diff --git a/libcxx/src/CMakeLists.txt b/libcxx/src/CMakeLists.txt
index 87b71f7..f8c4d3e 100644
--- a/libcxx/src/CMakeLists.txt
+++ b/libcxx/src/CMakeLists.txt
@@ -198,6 +198,7 @@ if (LIBCXX_ENABLE_SHARED)
       VERSION       "${LIBCXX_ABI_VERSION}.0"
       SOVERSION     "${LIBCXX_ABI_VERSION}"
       DEFINE_SYMBOL ""
+      POSITION_INDEPENDENT_CODE ON
   )
   cxx_add_common_build_flags(cxx_shared)
   cxx_set_common_defines(cxx_shared)
@@ -272,6 +273,7 @@ if (LIBCXX_ENABLE_STATIC)
       COMPILE_FLAGS "${LIBCXX_COMPILE_FLAGS}"
       LINK_FLAGS    "${LIBCXX_LINK_FLAGS}"
       OUTPUT_NAME   "c++"
+      POSITION_INDEPENDENT_CODE ON
   )
   cxx_add_common_build_flags(cxx_static)
   cxx_set_common_defines(cxx_static)
diff --git a/libcxxabi/src/CMakeLists.txt b/libcxxabi/src/CMakeLists.txt
index 889d751..f07d433 100644
--- a/libcxxabi/src/CMakeLists.txt
+++ b/libcxxabi/src/CMakeLists.txt
@@ -191,6 +191,7 @@ if (LIBCXXABI_ENABLE_SHARED)
       SOVERSION "1"
       VERSION "${LIBCXXABI_LIBRARY_VERSION}"
       DEFINE_SYMBOL ""
+      POSITION_INDEPENDENT_CODE ON
   )
 
   list(APPEND LIBCXXABI_BUILD_TARGETS "cxxabi_shared")
@@ -243,6 +244,7 @@ if (LIBCXXABI_ENABLE_STATIC)
       COMPILE_FLAGS "${LIBCXXABI_COMPILE_FLAGS}"
       LINK_FLAGS "${LIBCXXABI_LINK_FLAGS}"
       OUTPUT_NAME "c++abi"
+      POSITION_INDEPENDENT_CODE ON
     )
 
   if(LIBCXXABI_HERMETIC_STATIC_LIBRARY)
diff --git a/libunwind/src/CMakeLists.txt b/libunwind/src/CMakeLists.txt
index 05d3e59..093804f 100644
--- a/libunwind/src/CMakeLists.txt
+++ b/libunwind/src/CMakeLists.txt
@@ -141,6 +141,7 @@ if (LIBUNWIND_ENABLE_SHARED)
       OUTPUT_NAME "unwind"
       VERSION "1.0"
       SOVERSION "1"
+      POSITION_INDEPENDENT_CODE ON
   )
   list(APPEND LIBUNWIND_BUILD_TARGETS "unwind_shared")
   if (LIBUNWIND_INSTALL_SHARED_LIBRARY)
@@ -166,6 +167,7 @@ if (LIBUNWIND_ENABLE_STATIC)
       LINK_FLAGS "${LIBUNWIND_LINK_FLAGS}"
       LINKER_LANGUAGE C
       OUTPUT_NAME "unwind"
+      POSITION_INDEPENDENT_CODE ON
   )
 
   if(LIBUNWIND_HIDE_SYMBOLS)
-- 
2.7.4