[CMake] Support alternative C++ ABI library

[phosek]

Summary

Do not assume that every platform has libsupc++.

[smeenai]

CMakeLists.txt

162 ↗

(On Diff #188096)

What's the purpose of the leading semicolon?

165 ↗

(On Diff #188096)

Why c++ instead of c++abi?

167 ↗

(On Diff #188096)

Why stdc++ instead of supc++?

[phosek]

CMakeLists.txt

162 ↗

(On Diff #188096)

TBH I don't really know, this is being used in compiler-rt CMake. AFAIK this is only needed for CMake GUI which I don't have any experience with, I'm fine omitting it.

165 ↗

(On Diff #188096)

Not every platform ships separate C++ ABI library, e.g. in our toolchain we combine libc++abi and libc++ into a single library.

167 ↗

(On Diff #188096)

The same as above, I'm fine keeping it as supc++ to match the current behavior, although stdc++ seems safer to me.

[smeenai]

CMakeLists.txt

162 ↗

(On Diff #188096)

I would think it's allowing an empty string as one of the values, but I'm not sure why you'd want that? It's a GUI-only thing though and CMake doesn't enforce it, so I don't think it matters either way.

165 ↗

(On Diff #188096)

Fair enough. Last I checked you'd run into issues if libc++ and libc++abi were separate static libraries, since you wouldn't get the linker script that links libc++abi as well as libc++ in that case, but I don't think many people use that setup.

167 ↗

(On Diff #188096)

Yeah, I think I'd prefer to keep it as supc++ to match the existing behavior. I'm worried about the case where stdc++ is a static library and you need to link against supc++ separately, for example. (I'm not actually sure if that's a concern with libstdc++ or if they use a linker script even for their static libraries, but I know it's been an issue with libc++ in the past.)

[smeenai]

CMakeLists.txt

165 ↗

(On Diff #188096)

Sorry if I was unclear ... I was okay with this one being c++ for the reasons you stated (although the inconsistency with supc++ would be a bit strange). Is this still going to work for you, given you don't ship c++abi?

[phosek]

CMakeLists.txt

162 ↗

(On Diff #188096)

It should work for us, we ship c++abi on Fuchsia, we don't ship c++abi in our Linux host runtime, but for that one I'll have to use TEST_SUITE_CXX_ABI in any case.

[phosek]

CMakeLists.txt

162 ↗

(On Diff #188096)

More generally, I'm fine going with this, and re-evaluate it if it turns out we need c++.

[smeenai]

LGTM, thanks!

test-suite/trunk/CMakeLists.txt

set(TEST_SUITE_EXTRA_EXE_LINKER_FLAGS CACHE STRING
     "Extra flags for CMAKE_EXE_LINKER_FLAGS")
 mark_as_advanced(TEST_SUITE_EXTRA_C_FLAGS, TEST_SUITE_EXTRA_CXX_FLAGS,
                  TEST_SUITE_EXTRA_EXE_LINKER_FLAGS)
 set(CMAKE_C_CFLAGS "${CMAKE_C_CFLAGS} ${TEST_SUITE_EXTRA_C_FLAGS}")
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${TEST_SUITE_EXTRA_CXX_FLAGS}")
 set(CMAKE_EXE_LINKER_FLAGS
     "${CMAKE_EXE_LINKER_FLAGS} ${TEST_SUITE_EXTRA_EXE_LINKER_FLAGS}")
 
+# This is either directly the C++ ABI library or the full C++ library
+# which pulls in the ABI transitively.
+set(TEST_SUITE_CXX_ABI "default" CACHE STRING "Specify C++ ABI library to use.")
+set(CXXABIS "none default libstdc++ libsupc++ libc++ libc++abi")
+set_property(CACHE TEST_SUITE_CXX_ABI PROPERTY STRINGS "${CXXABIS}")
+if (TEST_SUITE_CXX_ABI STREQUAL "default")
+  if (APPLE OR CMAKE_SYSTEM_NAME MATCHES "FreeBSD|Fuchsia")
+    set(TEST_SUITE_CXX_ABI_LIBNAME "c++abi")
+  else()
+    set(TEST_SUITE_CXX_ABI_LIBNAME "supc++")
+  endif()
+else()
+  STRING(REGEX REPLACE "^lib" "" TEST_SUITE_CXX_ABI_LIBNAME ${TEST_SUITE_CXX_ABI})
+endif()
+
 include(TestSuite)
 include(SingleMultiSource)
 find_package(TCL)
 
 if(NOT DEFINED TARGET_OS)
   message(STATUS "Check target operating system - ${CMAKE_SYSTEM_NAME}")
   set(TARGET_OS ${CMAKE_SYSTEM_NAME})
 endif()

test-suite/trunk/MultiSource/Applications/obsequi/CMakeLists.txt

 list(APPEND CPPFLAGS -DCOUNTBITS16 -DLASTBIT16 -DCOUNTMOVES_TABLE)
 list(APPEND CPPFLAGS -DTWO_STAGE_GENERATION)
 if(SMALL_PROBLEM_SIZE)
   list(APPEND CPPFLAGS -DHASHCODEBITS=15)
 else()
   list(APPEND CPPFLAGS -DHASHCODEBITS=23)
 endif()
 if(NOT "${ARCH}" STREQUAL "PowerPC")
-  list(APPEND LDFLAGS -lsupc++)
+  list(APPEND LDFLAGS -l${TEST_SUITE_CXX_ABI_LIBNAME})
 endif()
 set(RUN_OPTIONS < input)
 llvm_multisource(Obsequi)
 llvm_test_data(Obsequi input)