Improvement: -latomic detection about fips HOT 13 CLOSED

if (FIPS_LINUX)
    check_function_exists(__atomic_fetch_add_4 HAVE___ATOMIC_FETCH_ADD_4)
    if (NOT HAVE___ATOMIC_FETCH_ADD_4)
        check_library_exists(atomic __atomic_fetch_add_4 "" HAVE_LIBATOMIC)
        if (HAVE_LIBATOMIC)
            fips_deps(atomic)
        endif()
    endif()
endif()

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Hmm interesting, didn't know that. What system(s) requires this?

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At least my system which is a ubuntu 14.10. I will check the relevant lib
versions once i am on the machine again - if needed.
Am 12.02.2015 17:40 schrieb "Andre Weissflog" [email protected]:

Hmm interesting, didn't know that. What system(s) requires this?

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Reply to this email directly or view it on GitHub
#54 (comment).

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Just digged a little bit deeper: They've moved atomics implementation since gcc 4.8 into libatomic.a - and this must be linked whenever you use atomics.

Do you think this patch can make it into fips? Or should I change something?

from fips.

Well, in fact gcc < 4.8 didn't support atomics at all... - just to clarify.

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I'd like to figure out first why Oryol is linking at all on Linux with gcc4.8 without explicitly linking libatomic... :) For instance I'm using std::atomic_exchange_explicit() and some operators (++, ...).

I'm on Linux Mint 17.1, based on Ubuntu 14.04.1 LTS
gcc -- version: gcc (Ubuntu 4.8.2-19ubuntu1) 4.8.2

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So... it looks like it worked in older Ubuntu and/or gcc versions but no longer in newer ones? What's your exact gcc version?

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gcc (Ubuntu 4.9.1-16ubuntu6) 4.9.1

lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 14.10
Release: 14.10
Codename: utopic

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btw. oryol links for me, too - which is very weird. Maybe not all symbols are put into the atomic lib.

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in simpleai this works:

cd /home/mgerhardy/dev/simpleai/src/run && /usr/bin/cmake -E cmake_link_script CMakeFiles/simpleai-run.dir/link.txt --verbose=1
/usr/bin/c++ -std=c++11 -Wall -Wextra -fno-exceptions CMakeFiles/simpleai-run.dir/GameEntity.cpp.o CMakeFiles/simpleai-run.dir/Main.cpp.o -o simpleai-run -L/home/mgerhardy/dev/simpleai/src/ai -rdynamic ../ai/libsimpleai.a -lpthread -latomic ../libs/lua/liblua.a -ldl -Wl,-rpath,/home/mgerhardy/dev/simpleai/src/ai

while this doesn't:

cd /home/mgerhardy/dev/simpleai/src/run && /usr/bin/cmake -E cmake_link_script CMakeFiles/simpleai-run.dir/link.txt --verbose=1
/usr/bin/c++ -std=c++11 -Wall -Wextra -fno-exceptions CMakeFiles/simpleai-run.dir/GameEntity.cpp.o CMakeFiles/simpleai-run.dir/Main.cpp.o -o simpleai-run -L/home/mgerhardy/dev/simpleai/src/ai -rdynamic ../ai/libsimpleai.a -lpthread -latomic ../libs/lua/liblua.a -ldl -Wl,-rpath,/home/mgerhardy/dev/simpleai/src/ai

the only difference is -latomic

CMakeFiles/simpleai-run.dir/GameEntity.cpp.o: In Funktion std::atomic<ai::Vector3f>::store(ai::Vector3f, std::memory_order)': GameEntity.cpp:(.text._ZNSt6atomicIN2ai8Vector3fEE5storeES1_St12memory_order[_ZNSt6atomicIN2ai8Vector3fEE5storeES1_St12memory_order]+0x27): Nicht definierter Verweis auf__atomic_store'
CMakeFiles/simpleai-run.dir/GameEntity.cpp.o: In Funktion std::atomic<ai::Vector3f>::load(std::memory_order) const': GameEntity.cpp:(.text._ZNKSt6atomicIN2ai8Vector3fEE4loadESt12memory_order[_ZNKSt6atomicIN2ai8Vector3fEE4loadESt12memory_order]+0x42): Nicht definierter Verweis auf__atomic_load'
collect2: error: ld returned 1 exit status

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Strange. Would you mind providing a pull request for fips? I think this should go into cmake-toolchains/linux.toolchain.cmake. There's already a couple of standard libs defined (-lpthread and -lrt),
additionally to your detection whether atomic exists, you could also limit this to gcc with an if (FIPS_GCC).

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created a pull request.

while we are on it - there are systems that don't have librt - they have clock_gettime somewhere else (afair in libc directly - but my memories might be wrong, fixed that for ufoai a felt decade ago)

I will try to fix it in a proper cmake way and provide another pull request.

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Cleaning up leftover tickets...

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