Add a linker script to version LLVM symbols

Summary:
This patch adds a very simple linker script to version the lib's symbols
and thus trying to avoid crashes if an application loads two different
LLVM versions (as long as they do not share data between them).

Note that we deliberately *don't* make LLVM_5.0 depend on LLVM_4.0:
they're incompatible and the whole point of this patch is
to tell the linker that.


Avoid unexpected crashes when two LLVM versions are used in the same process.

Author: Rebecca N. Palmer <[email protected]>
Author: Lisandro Damían Nicanor Pérez Meyer <[email protected]>
Author: Sylvestre Ledru <[email protected]>
Bug-Debian:  https://bugs.debian.org/848368


Reviewers: beanz, rnk

Reviewed By: rnk

Subscribers: mgorny, llvm-commits

Differential Revision: https://reviews.llvm.org/D31524

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@300496 91177308-0d34-0410-b5e6-96231b3b80d8

cmake/modules/AddLLVM.cmake

@@ -81,8 +81,9 @@ function(add_llvm_symbol_exports target_name export_file)
     # Gold and BFD ld require a version script rather than a plain list.
     set(native_export_file "${target_name}.exports")
     # FIXME: Don't write the "local:" line on OpenBSD.
+    # in the export file, also add a linker script to version LLVM symbols (form: LLVM_N.M)
     add_custom_command(OUTPUT ${native_export_file}
-      COMMAND echo "{" > ${native_export_file}
+      COMMAND echo "LLVM_${LLVM_VERSION_MAJOR}.${LLVM_VERSION_MINOR} {" > ${native_export_file}
       COMMAND grep -q "[[:alnum:]]" ${export_file} && echo "  global:" >> ${native_export_file} || :
       COMMAND sed -e "s/$/;/" -e "s/^/    /" < ${export_file} >> ${native_export_file}
       COMMAND echo "  local: *;" >> ${native_export_file}

tools/llvm-shlib/CMakeLists.txt

@@ -38,8 +38,12 @@ add_llvm_library(LLVM SHARED DISABLE_LLVM_LINK_LLVM_DYLIB SONAME ${SOURCES})
 
 list(REMOVE_DUPLICATES LIB_NAMES)
 if(("${CMAKE_SYSTEM_NAME}" STREQUAL "Linux") OR (MINGW) OR ("${CMAKE_SYSTEM_NAME}" STREQUAL "FreeBSD") OR ("${CMAKE_SYSTEM_NAME}" STREQUAL "DragonFly")) # FIXME: It should be "GNU ld for elf"
+  configure_file(
+  ${CMAKE_CURRENT_SOURCE_DIR}/simple_version_script.map.in
+  ${LLVM_LIBRARY_DIR}/tools/llvm-shlib/simple_version_script.map)
+
   # GNU ld doesn't resolve symbols in the version script.
-  set(LIB_NAMES -Wl,--whole-archive ${LIB_NAMES} -Wl,--no-whole-archive)
+  set(LIB_NAMES -Wl,--version-script,${LLVM_LIBRARY_DIR}/tools/llvm-shlib/simple_version_script.map -Wl,--whole-archive ${LIB_NAMES} -Wl,--no-whole-archive)
 elseif("${CMAKE_SYSTEM_NAME}" STREQUAL "Darwin")
   set(LIB_NAMES -Wl,-all_load ${LIB_NAMES})
 endif()

tools/llvm-shlib/simple_version_script.map.in

@@ -0,0 +1 @@
+LLVM_@LLVM_VERSION_MAJOR@.@LLVM_VERSION_MINOR@ { global: *; };