Fix building against libc++ (#12)

When building for libc++, the C++ runtime is still necessary for std::mutex.
By default explicitly build against libstdc++ to avoid the dependency with
an option to explicitly choose libc++.

CMakeLists.txt

@@ -74,25 +74,41 @@ set(OTFCPT_OMP_SOURCES
 )
 
 
+set(STDCPLUS_COMPILE_FLAGS -fno-rtti -fno-exceptions -ffunction-sections -fdata-sections)
+set(STDCPLUS_LINK_FLAGS -fno-rtti -fno-exceptions -fno-rtti -fno-exceptions -nostdlib++ -Wl,--gc-sections)
+
+if (CMAKE_C_COMPILER_ID STREQUAL "Clang")
+  option(OTFCPT_USE_LLVM_LIBCPP "Use LLVM libc++, which might reduce portability." OFF)
+  if(OTFCPT_USE_LLVM_LIBCPP)
+    message(STATUS "Building with LLVM libc++ was requested, which might limit portability and compatibility with application/library code compiled with gcc.")
+    set(STDCPLUS_COMPILE_FLAGS -stdlib=libc++)
+    set(STDCPLUS_LINK_FLAGS -stdlib=libc++)
+  else()
+    message(STATUS "For portability, OTF-CPT is built without dependency to a C++ runtime library")
+    set(STDCPLUS_COMPILE_FLAGS ${STDCPLUS_COMPILE_FLAGS} -stdlib=libstdc++)
+    set(STDCPLUS_LINK_FLAGS ${STDCPLUS_LINK_FLAGS} -stdlib=libstdc++)
+  endif()
+endif ()
+
 set(WRAP_FLAGS -s -n)
 add_wrapped_file(gen-nb-wrappers.cpp gen-nb-wrappers.w)
 add_wrapped_file(gen-wrappers.cpp gen-wrappers.w)
 
 add_library(OTFCPT SHARED ${OTFCPT_SOURCES})
 target_link_libraries(OTFCPT ${MPI_C_LIBRARIES})
 target_compile_definitions(OTFCPT PUBLIC -DUSE_MPI=1)
-target_link_options(OTFCPT PUBLIC -fno-rtti -fno-exceptions -nostdlib++ -Wl,--gc-sections)
-target_compile_options(OTFCPT PUBLIC -fno-rtti -fno-exceptions -ffunction-sections -fdata-sections)
+target_link_options(OTFCPT PUBLIC ${STDCPLUS_LINK_FLAGS})
+target_compile_options(OTFCPT PUBLIC ${STDCPLUS_COMPILE_FLAGS})
 
 add_library(OTFCPT_omp SHARED ${OTFCPT_OMP_SOURCES})
-target_link_options(OTFCPT_omp PUBLIC -fno-rtti -fno-exceptions -nostdlib++ -Wl,--gc-sections)
-target_compile_options(OTFCPT_omp PUBLIC -fno-rtti -fno-exceptions -ffunction-sections -fdata-sections)
+target_link_options(OTFCPT_omp PUBLIC ${STDCPLUS_LINK_FLAGS})
+target_compile_options(OTFCPT_omp PUBLIC ${STDCPLUS_COMPILE_FLAGS})
 
 add_library(OTFCPT_static STATIC ${OTFCPT_SOURCES})
 target_link_libraries(OTFCPT_static ${MPI_C_LIBRARIES})
 target_compile_definitions(OTFCPT_static PUBLIC -DUSE_MPI=1)
-target_link_options(OTFCPT_static PUBLIC -fno-rtti -fno-exceptions -nostdlib++ -Wl,--gc-sections)
-target_compile_options(OTFCPT_static PUBLIC -fno-rtti -fno-exceptions -ffunction-sections -fdata-sections)
+target_link_options(OTFCPT_static PUBLIC ${STDCPLUS_LINK_FLAGS})
+target_compile_options(OTFCPT_static PUBLIC ${STDCPLUS_COMPILE_FLAGS})
 
 if (EXISTS ${CMAKE_CURRENT_LIST_DIR}/external/FileCheck/CMakeLists.txt)
     add_subdirectory(${CMAKE_CURRENT_LIST_DIR}/external/FileCheck EXCLUDE_FROM_ALL)

README.md

@@ -3,7 +3,7 @@
 
 Tool to collect and report model factors (aka. fundamental performance factors) for hybrid MPI + OpenMP applications on-the-fly.
 
-## Build with CMake
+## Building with CMake
 The C/C++ compiler needs to support OMPT (which is provided by icc/clang and others, but not gcc)
 ### Basic Cmake
 ```
@@ -13,7 +13,7 @@ cmake ../
 make -j8
 ```
 
-### Cmake with Clang
+### Building with Clang
 To use clang with IntelMPI/OpenMPI/MPICH, export the following env variables first:
 ```
 export MPICH_CC=clang; export MPICH_CXX=clang++;
@@ -24,7 +24,17 @@ cmake ../
 make -j8
 ```
 
-### Cmake with MPICH + Clang on Ubuntu
+### Using libc++ with Clang-based compilers
+For broad compatibility with applications and libraries built with mixed
+compiler setups (e.g. gfortran + clang++), OTF-CPT tries to avoid dependency 
+to a C++ runtime library. If GNU C++ headers are available, they are 
+preferred for building OTF-CPT (which is also the default). 
+
+If no GNU C++ headers are available, OTF-CPT can be built by explicitly using
+LLVM's C++ runtime library (libc++) by configuring OTF-CPT with the cmake
+flag `-DOTFCPT_USE_LLVM_LIBCPP=ON`.
+
+### Building with MPICH + Clang on Ubuntu
 The MPICH compiler wrapper on Ubuntu bricks MPI detection in cmake, work-around as following:
 ```
 export MPICH_CC=clang; export MPICH_CXX=clang++;
@@ -34,7 +44,7 @@ CC=mpicc.mpich CXX=mpicxx.mpich LDFLAGS=-flto=auto cmake ../
 make -j8
 ```
 
-### Cmake with OpenMPI + Clang on Ubuntu
+### Building with OpenMPI + Clang on Ubuntu
 ```
 export OMPI_CC=clang; export OMPI_CXX=clang++;
 mkdir BUILD