CMake does not propagate flags to build

adek · July 18, 2015, 3:41am

'-DCMAKE_CXX_FLAGS=-fno-omit-frame-pointer -Wno-maybe-uninitialized
-fPIC -fPIE'
-- The C compiler identification is GNU 4.8.1
-- The CXX compiler identification is GNU 4.8.1
-- Check for working C compiler:
/home/engshare/third-party2/gcc/4.8.1/centos6-native/cc6c9dc/bin/gcc
-- Check for working C compiler:
/home/engshare/third-party2/gcc/4.8.1/centos6-native/cc6c9dc/bin/gcc --
works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler:
/home/engshare/third-party2/gcc/4.8.1/centos6-native/cc6c9dc/bin/g++
-- Check for working CXX compiler:
/home/engshare/third-party2/gcc/4.8.1/centos6-native/cc6c9dc/bin/g++ --
works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Found PythonInterp:
/home/engshare/third-party2/python/2.7.5/centos6-native/da39a3e/bin/python2.7
(found version "2.7.5")
-- Looking for unwind.h
-- Looking for unwind.h - found
-- Performing Test COMPILER_RT_HAS_FPIC_FLAG
-- Performing Test COMPILER_RT_HAS_FPIC_FLAG - Success
-- Performing Test COMPILER_RT_HAS_FPIE_FLAG
-- Performing Test COMPILER_RT_HAS_FPIE_FLAG - Success
-- Performing Test COMPILER_RT_HAS_FNO_BUILTIN_FLAG
-- Performing Test COMPILER_RT_HAS_FNO_BUILTIN_FLAG - Success
-- Performing Test COMPILER_RT_HAS_FNO_EXCEPTIONS_FLAG
-- Performing Test COMPILER_RT_HAS_FNO_EXCEPTIONS_FLAG - Success
-- Performing Test COMPILER_RT_HAS_FOMIT_FRAME_POINTER_FLAG
-- Performing Test COMPILER_RT_HAS_FOMIT_FRAME_POINTER_FLAG - Success

Is it still related to this:
http://lists.cs.uiuc.edu/pipermail/llvmdev/2014-March/071394.html

Adrian Zgorzałek

pete · July 20, 2015, 4:34pm

Hi Adrian

I’m not sure if the CMAKE_CXX_FLAGS is used in LLVM. We have our own flags for different configurations. I don’t remember if our ones inherit from CMAKE_CXX_FLAGS or override it completely. Anyway, they are:
- CMAKE_CXX_FLAGS_DEBUG
- CMAKE_CXX_FLAGS_MINSIZEREL
- CMAKE_CXX_FLAGS_RELEASE
- CMAKE_CXX_FLAGS_RELWITHDEBINFO

The one of those you get depends on what you set CMAKE_BUILD_TYPE to. Options are ‘Debug, Release, RelWithDebInfo, MinSizeRel’

Cheers,
Pete

adek · July 20, 2015, 4:36pm

Hey Pete,

I also tried CMAKE_CXX_FLAGS_RELEASE
with the same effect.

pete · July 20, 2015, 4:42pm

Hey Pete,

I also tried CMAKE_CXX_FLAGS_RELEASE
with the same effect.

Ah, thats me out of ideas

Can you post your full cmake invocation and maybe even the cmake log. I don’t know compiler-rt so i may not be any help, but other people who can help would find that useful too.

Cheers,
Pete

Chris_Bieneman · July 20, 2015, 6:23pm

Adrian,

What makes you think CMAKE_CXX_FLAGS isn’t being respected?

The tests will always occur regardless of whether or not you set the CXX_FLAGS explicitly.

-Chris

Martin_J_O_Riordan1 · July 20, 2015, 8:39pm

I regularly use '-DCMAKE_CXX_FLAGS' when configuring CLang/LLVM to distinguish my builds (Alpha/Beta/Final) or to build custom versions, usually by adding additional '-D' flags, but I discovered I had to add the ':STRING' qualifier to it when invoking 'cmake'. With 'gmake' this is equivalent to '--with-extra-options="whatever flags":

-DCMAKE_CXX_FLAGS:STRING="whatever flags"

This works regardless of whether it is a Debug or Release build.

All the best,

MartinO

adek · July 20, 2015, 9:23pm

Hey,

Thanks for ideas. I tried them on, but none of them succeeded.

If I remove this line:

github.com

llvm-mirror/compiler-rt/blob/c9d8d35a5c2bdd6a0dd41f1b6cf3afb822df6a6e/CMakeLists.txt#L207


      
          
          
# Emulate C99 and C++11's __func__ for MSVC prior to 2013 CTP.
          if(NOT COMPILER_RT_HAS_FUNC_SYMBOL)
            add_definitions(-D__func__=__FUNCTION__)
          endif()
          
          
# Provide some common commmandline flags for Sanitizer runtimes.
          append_list_if(COMPILER_RT_HAS_FPIC_FLAG -fPIC SANITIZER_COMMON_CFLAGS)
          append_list_if(COMPILER_RT_HAS_FNO_BUILTIN_FLAG -fno-builtin SANITIZER_COMMON_CFLAGS)
          append_list_if(COMPILER_RT_HAS_FNO_EXCEPTIONS_FLAG -fno-exceptions SANITIZER_COMMON_CFLAGS)
          append_list_if(COMPILER_RT_HAS_FOMIT_FRAME_POINTER_FLAG -fomit-frame-pointer SANITIZER_COMMON_CFLAGS)
          append_list_if(COMPILER_RT_HAS_FUNWIND_TABLES_FLAG -funwind-tables SANITIZER_COMMON_CFLAGS)
          append_list_if(COMPILER_RT_HAS_FNO_STACK_PROTECTOR_FLAG -fno-stack-protector SANITIZER_COMMON_CFLAGS)
          append_list_if(COMPILER_RT_HAS_FNO_SANITIZE_SAFE_STACK_FLAG -fno-sanitize=safe-stack SANITIZER_COMMON_CFLAGS)
          append_list_if(COMPILER_RT_HAS_FVISIBILITY_HIDDEN_FLAG -fvisibility=hidden SANITIZER_COMMON_CFLAGS)
          append_list_if(COMPILER_RT_HAS_FNO_FUNCTION_SECTIONS_FLAG -fno-function-sections SANITIZER_COMMON_CFLAGS)
          append_list_if(COMPILER_RT_HAS_FNO_LTO_FLAG -fno-lto SANITIZER_COMMON_CFLAGS)
          
          
if(MSVC)
            # Replace the /M[DT][d] flags with /MT, and strip any definitions of _DEBUG,
            # which cause definition mismatches at link time.

Everything is correctly built with -fno-omit-frame-pointer.

Any suggestion why it would be the case?

Thanks,
Adrian

Chris_Bieneman1 · July 20, 2015, 9:27pm

Wait… This is just for compiler-rt?

+Samsonov

I don’t know if we explicitly don’t support -fno-omit-frame-pointer for compiler-rt, but in general compiler-rt is generally built differently from LLVM & Clang for a reason.

Why do you need -fno-omit-frame-pointer for compiler-rt?

-Chris

adek · July 20, 2015, 10:00pm

This is just for compiler-rt. The reason for having
-fno-omit-frame-pointer is that tools like
Perf Wiki would work on ASAN
binaries.

Adrian

Chris_Bieneman1 · July 20, 2015, 10:25pm

At the moment I don’t believe we support building ASAN with -fno-omit-frame-pointer because doing so would likely have significant adverse impact on performance. Samsonov would know better, but especially if you’re looking to run profiling tools you really don’t want frame pointers for the runtime libraries.

-Chris

Alexey_Samsonov1 · July 21, 2015, 6:40pm

Sorry for the late response.

Yes, we explicitly add -fomit-frame-pointer when we build sanitizer
runtimes, and it may override what you set in CMAKE_CXX_FLAGS. It is indeed
related to performance overhead, which is especially critical for slower
tools like ThreadSanitizer, which inserts a call into runtime for *every*
load/store in the original problem.