[llvm] r319069 - [cmake] Pass -Wl, -z, nodelete on Linux to prevent unloading

[Michal Gorny via llvm-commits]

Author: mgorny
Date: Mon Nov 27 10:34:52 2017
New Revision: 319069

URL: http://llvm.org/viewvc/llvm-project?rev=319069&view=rev
Log:
[cmake] Pass -Wl,-z,nodelete on Linux to prevent unloading

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

Modified:
    llvm/trunk/cmake/modules/HandleLLVMOptions.cmake

Modified: llvm/trunk/cmake/modules/HandleLLVMOptions.cmake
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/cmake/modules/HandleLLVMOptions.cmake?rev=319069&r1=319068&r2=319069&view=diff
==============================================================================
--- llvm/trunk/cmake/modules/HandleLLVMOptions.cmake (original)
+++ llvm/trunk/cmake/modules/HandleLLVMOptions.cmake Mon Nov 27 10:34:52 2017
@@ -151,6 +151,14 @@ if(NOT (${CMAKE_SYSTEM_NAME} MATCHES "Da
   set(CMAKE_SHARED_LINKER_FLAGS "${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})