[DynInst_API:] [PATCH 1/1] cmake: make the c++11 abi configurable, default unset

[Josh Stone <jistone@xxxxxxxxxx>]

GCC 5 made several ABI changes for C++11 support, but they also kept
support for the older ABI.  The macro _GLIBCXX_USE_CXX11_ABI can force
which mode you compile against.

Fedora 22 shipped with GCC 5 configured to use the old ABI by default,
as if -D_GLIBCXX_USE_CXX11_ABI=0, and Fedora 23 moved to the new ABI.
In either case you could make a different choice with that macro, but
any APIs you expose will be ABI-tagged, and programs you link with must
use the same choice.  For working in a Linux distribution, it's usually
best to leave it at the default.

Commit dbd452640a57 forced the old ABI unconditionally.  This patch adds
a cmake USE_CXX11_ABI setting, left blank to use the compiler default,
or set to a cmake boolean to force the new ABI on or off.

References:
  http://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/
  http://developers.redhat.com/blog/2015/02/10/gcc-5-in-fedora/
---
 cmake/shared.cmake | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/cmake/shared.cmake b/cmake/shared.cmake
index 88b0b6aa86fe..699c5b489796 100644
--- a/cmake/shared.cmake
+++ b/cmake/shared.cmake
@@ -112,7 +112,14 @@ if(PLATFORM MATCHES nt OR PLATFORM MATCHES windows)
   endif()
 endif()
 
-add_definitions(-D_GLIBCXX_USE_CXX11_ABI=0)
+set (USE_CXX11_ABI "" CACHE STRING "Override the default GNU C++11 ABI setting")
+if (NOT ("${USE_CXX11_ABI}" STREQUAL ""))
+  if (${USE_CXX11_ABI})
+    add_definitions(-D_GLIBCXX_USE_CXX11_ABI=1)
+  else()
+    add_definitions(-D_GLIBCXX_USE_CXX11_ABI=0)
+  endif()
+endif()
 
 #
 # DyninstConfig.cmake
-- 
2.5.5