Alexander,

Thanks for the review, updated commit message as you suggested.

>Четверг,  5 декабря 2019, 4:49 +03:00 от Alexander Turenko <alexander.turenko@tarantool.org>:
>
>LGTM.
>
>I'm okay with the approach I proposed, of course :) My review would be
>insufficient.
>
>Serge, can you do the second review?
>
>WBR, Alexander Turenko.
>
>> build: fix unit tests build with lrt
>
>Nit: librt or -ltr
>
>Or just 'on CentOS 6'. All those details about librt are described in
>the commit message below, while the header would be better if it will
>give us an idea why the commit was made.
Corrected commit message added 'on CentOS 6' add '-lrt', (use of 'librt' exceeded the limit of the commit message length)
>
>> After the commit 77fa45bd05f8cdd4c0f9bad85185ef5b61528d49
>> ('lua: add fiber.top() listing fiber cpu consumption')
>> the unit tests builds failed like:
>> 
>> /opt/rh/devtoolset-6/root/usr/libexec/gcc/x86_64-redhat-linux/6.3.1/ld:
>>   ../../src/lib/core/libcore.a(fiber.c.o): undefined reference to symbol
>>   'clock_gettime@@GLIBC_2.2.5'
>> //lib64/librt.so.1: error adding symbols: DSO missing from command line
>> collect2: error: ld returned 1 exit status
>> test/unit/CMakeFiles/cbus.test.dir/build.make:108: recipe for target
>>   'test/unit/cbus.test' failed
>> make[2]: *** [test/unit/cbus.test] Error 1
>> 
>> Found that fiber.cc is using now clock_gettime(), which requires -lrt
>> with glibc. To fix it added librt dependency for core library for glibc.
>> Due to glibc requires for -lrt for clock_gettime() only for some
>> versions, check 'man clock_gettime.2':
>>   'Link with -lrt (only for glibc versions before 2.17).'
>> the check whether is able to use clock_gettime() w/o librt library is
>> added.
>> 
>> Close #4639
>> ---
>> 
>> Github:  https://github.com/tarantool/tarantool/tree/avtikhon/gh-4639-lrt-suggested-full-ci
>> Issue:  https://github.com/tarantool/tarantool/issues/4639
>> 
>>  CMakeLists.txt              | 6 ++++++
>>  src/lib/core/CMakeLists.txt | 8 ++++++++
>>  2 files changed, 14 insertions(+)
>> 
>> diff --git a/CMakeLists.txt b/CMakeLists.txt
>> index 7d6c0846e..ca968eb8d 100644
>> --- a/CMakeLists.txt
>> +++ b/CMakeLists.txt
>> @@ -116,6 +116,12 @@ else ()
>>      set(HAVE_CLOCK_GETTIME ${HAVE_CLOCK_GETTIME_DECL})
>>  endif ()
>>  set(CMAKE_REQUIRED_LIBRARIES "")
>> +# According to `man 2 clockgettime` the glibc wrapper requires
>> +# -lrt on glibc versions before 2.17. We need to check whether
>> +# the function is available without -lrt to set this linker option
>> +# conditionally.
>> +check_function_exists(clock_gettime HAVE_CLOCK_GETTIME_WITHOUT_RT)
>> +
>>  check_symbol_exists(__get_cpuid cpuid.h HAVE_CPUID)
>> 
>>  # Checks for libev
>> diff --git a/src/lib/core/CMakeLists.txt b/src/lib/core/CMakeLists.txt
>> index e60b5199e..8623aa0de 100644
>> --- a/src/lib/core/CMakeLists.txt
>> +++ b/src/lib/core/CMakeLists.txt
>> @@ -46,3 +46,11 @@ target_link_libraries(core salad small uri decNumber ${LIBEV_LIBRARIES}
>>  if (ENABLE_BACKTRACE AND NOT TARGET_OS_DARWIN)
>>      target_link_libraries(core gcc_s ${UNWIND_LIBRARIES})
>>  endif()
>> +
>> +# Since fiber.top() introduction, fiber.cc, which is part of core
>> +# library, depends on clock_gettime() syscall, so we should set
>> +# -lrt when it is appropriate. See a comment for
>> +# HAVE_CLOCK_GETTIME_WITHOUT_RT in ${REPO}/CMakeLists.txt.
>> +if ("${HAVE_CLOCK_GETTIME}" AND NOT "${HAVE_CLOCK_GETTIME_WITHOUT_RT}")
>> +    target_link_libraries(core rt)
>> +endif()
>> -- 
>> 2.17.1
>> 


-- 
Alexander Tikhonov