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[cmake] Pass -Wl,-z,nodelete on Linux to prevent unloading

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Prevent unloading shared libraries on Linux when dlclose() is called.
This is necessary since command-line option parsing API relies on
registering the global option instances in the option parser instance
which can be loaded in a different shared library.

Given that we can't reliably remove those options when a library is
unloaded, the parser ends up containing dangling references. Since glibc
has relatively complex library unloading rules, some of the LLVM
libraries can be unloaded while others (including the Support library)
stay loaded causing quite a mayhem. To reliably prevent that, just
forbid unloading all libraries -- it's a very bad idea anyway.

While the issue arguably happens only with BUILD_SHARED_LIBS, it may
affect any library reusing llvm::cl interface.

Based on patch provided Ross Hayward on https://bugs.gentoo.org/617154.
Previously hit by Fedora back in Feb 2016:
https://lists.freedesktop.org/archives/mesa-dev/2016-February/107242.html

Differential Revision: https://reviews.llvm.org/D40459

llvm-svn: 319105
This commit is contained in:
Michal Gorny 2017-11-27 22:23:09 +00:00
parent 125dd76f1e
commit 6d3f09db6e
2 changed files with 15 additions and 0 deletions
cmake/modules
HandleLLVMOptions.cmake
unittests/Support/DynamicLibrary
CMakeLists.txt

8
cmake/modules/HandleLLVMOptions.cmake

@ -151,6 +151,14 @@ if(NOT (${CMAKE_SYSTEM_NAME} MATCHES "Darwin" OR WIN32 OR CYGWIN OR
set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -Wl,-z,defs")
endif()
# Pass -Wl,-z,nodelete. This makes sure our shared libraries are not unloaded
# by dlclose(). We need that since the CLI API relies on cross-references
# between global objects which became horribly broken when one of the libraries
# is unloaded.
if(${CMAKE_SYSTEM_NAME} MATCHES "Linux")
set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -Wl,-z,nodelete")
endif()
function(append value)
foreach(variable ${ARGN})

7
unittests/Support/DynamicLibrary/CMakeLists.txt

@ -24,5 +24,12 @@ function(dynlib_add_module NAME)
add_dependencies(DynamicLibraryTests ${NAME})
endfunction(dynlib_add_module)
# Revert -Wl,-z,nodelete on this test since it relies on the file
# being unloaded.
if(${CMAKE_SYSTEM_NAME} MATCHES "Linux")
string(REPLACE "-Wl,-z,nodelete" "" CMAKE_SHARED_LINKER_FLAGS
${CMAKE_SHARED_LINKER_FLAGS})
endif()
dynlib_add_module(PipSqueak)
dynlib_add_module(SecondLib)