Bru*_*ams 7 build-process build cmake meson-build
I have an issue with the generation of makefiles stage of CMake being slow which is similar to this unanswered question:
CMake is slow to generate makefiles
My project is made up of a top level CMakeLists.txt file which uses add_subdirectory() to add various subprojects for individual library and executable components.
For a given component, the CMakeLists.txt file contains something like:
add_library(mylib SHARED
sourceFile1.cpp
sourceFile2.cpp
...
)
I can build just the contents of that directory using:
make mylib
If I modify the CMakeLists.txt file in the sub-directory (which I've been doing a lot as part of a migration from pure Makefiles to CMake) then run make it correctly re-runs CMake to update the configuration as if I'd run make rebuild_cache.
However, I notice that it in fact reconfigures the entire project. I really want for CMake to be clever enough to know it only needs to regenerate the Makefile in the current directory and sub-directories.
Is there a better way to structure a CMake project to achieve this? I see some people use project() for each CMakeLists.txt in each sub-project. In general, is this a good idea?
Alternatively/additionally is there some way to speed up the generation step of CMake? (currently I have 60s+)
Bonus points if you want to discuss why CMake itself should or shouldn't be able to run in parallel (imagine a cmake -j).
我已经将meson-build标签添加为适度的赏金,但仅凭它还没有吸引足够的注意力以保证答案.正是这种问题可能导致人们切换到构建系统进行介子构建(假设它没有类似的问题)或类似的东西.
如果不将源修改为CMake,则可能无法正确回答.虽然我需要解释CMake的工作方式和/或存在缺陷,但要获得赏金.
澄清:在我的情况下,生成步骤很慢.配置本身足够快,但CMake在输出" - 配置完成"和" - 生成完成"之间相当长一段时间.
对于完整的缓存重建,我运行:
make -n rebuild_cache
Running CMake to regenerate build system... using Makefile generator -- FOOBAR_VERSION: 01.02.03 -- Configuring done -- Generating done -- Build files have been written to: /home/brucea/work/depot/emma/main/cmake real 74.87 user 1.74 sys 1.02
Under the hood this runs:
cmake -H<source dir> -B<build dir>
I presume -B is a synonym for --build. Neither option is described correctly in the documentation. -H is the root of the source directory (not the same as --help as the documentation would have you believe).
It's fast to get to the output of "Configuring done", but slow from there:
For example,
15:44:14 execve("/usr/local/bin/cmake",
>grep Generating cmake_strace.log
>grep "Configuring" cmake_strace.log
15:44:15 write(1, "-- Configuring done\n", 20-- Configuring done
15:45:01 write(1, "-- Generating done\n", 19-- Generating done
>grep "Build files" cmake_strace.log
15:45:22 write(1, "-- Build files have been written"..., 77-- Build files have been written to:
If editing a single CMakeLists.txt file in a subdirectory, and
then running make -n, it runs:
cd /home/project/cmake && /usr/local/bin/cmake -H/home/project/cmake -B/home/project/cmake --check-build-system CMakeFiles/Makefile.cmake 0
--check-build-system is another undocumented option.
The effect is the same - regenerate the whole build system, not just the current subtree. There is no difference in behaviour between an in-source and an out-of-source build.
If I run a trace, e.g.:
strace -r cmake --trace -H/home/project/cmake -B/home/project/cmake 2>&1 | tee cmake_rebuild_cache.log
sort -r cmake_rebuild_cache.log | uniq
The majority of time spent seems to be spent on (or between) open, access & unlink calls.
The length of each task is quite variable, but the huge number of them builds up. I have no idea what the Labels.json and Labels.txt files are about (something internal to CMake).
One run:
49.363537 open("/home/projectbar/main/test/foo2bar/CMakeFiles/test2.foo2bar.testViewingSource1.dir/build.make", O_RDONLY) = 5
1.324777 access("/home/projectbar/main/test/performance/CMakeFiles/performancetest.chvcthulhu.testChvcthulhuPerformance2.dir", R_OK) = 0
0.907807 access("/home/projectbar/main/test/foo2bar/CMakeFiles/test2.foo2bar.testPeripheralConnection2.dir", R_OK) = 0
0.670272 unlink("/home/projectbar/main/src/foo2bar/Foo2Bar/CMakeFiles/foo2bar_lib.dir/progress.make.tmp") = -1 ENOENT (No such file or directory)
0.600272 access("/home/projectbar/main/test/foo2bar/testFilesModel2.ok", R_OK) = 0
0.599010 access("/home/projectbar/main/test/hve2snafu/testInvalidByte2c.ok", R_OK) = 0
0.582466 read(5, "openjdk version \"1.8.0_71\"\nOpenJ"..., 1024) = 130
0.570540 writev(3, [{"# CMAKE generated file: DO NOT E"..., 8190}, {"M", 1}], 2) = 8191
0.553576 close(4) = 0
0.448811 unlink("/home/projectbar/main/test/snafu2hve/CMakeFiles/test2.snafu2hve.testNoProbes2.dir/progress.make.tmp") = -1 ENOENT (No such file or directory)
0.431559 access("/home/projectbar/main/src/foo2bar/Foo2Bar/CMakeFiles/foo2bar_lib.dir", R_OK) = 0
0.408003 unlink("/home/projectbar/main/test/lachesis/CMakeFiles/test2.lachesis.testBadSequenceNumber1.dir/progress.make.tmp") = -1 ENOENT (No such file or directory)
0.407120 write(4, "# The set of languages for which"..., 566) = 566
0.406674 write(3, "# CMAKE generated file: DO NOT E"..., 675) = 675
0.383892 read(3, "ewingPeriod.cpp.o -c /home/bruce"..., 8191) = 8191
0.358490 unlink("/home/projectbar/main/cmake/CMakeFiles/mklinks.chvdiff.dir/progress.make.tmp") = -1 ENOENT (No such file or directory)
Another run of the same command:
2.009451 unlink("/home/projectbar/main/cmake/CMakeFiles/mklinks.lachesis.dir/Labels.json") = -1 ENOENT (No such file or directory)
) = 20
) = 19
1.300387 access("/home/projectbar/main/test/chvedit/CMakeFiles/test2.chvedit.tefooultiMatchFactoringEdit2.dir", R_OK) = 0
1.067957 access("/home/projectbar/main/test/chvedit/CMakeFiles/test2.chvedit.tefooultiMatchFactoringEdit2.dir", R_OK) = 0
) = 1
0.885854 unlink("/home/projectbar/main/src/gorkyorks2bar/CMakeFiles/doxygen.correct.gorkyorks2bar.dir/Labels.json") = -1 ENOENT (No such file or directory)
0.854539 access("/home/projectbar/main/test/reportImpressions/ReportImpressions/CMakeFiles/testsuite1_reportImpressions.dir", R_OK) = 0
0.791741 unlink("/home/projectbar/main/cmake/CMakeFiles/mklinks.bar_models.dir/progress.make.tmp") = -1 ENOENT (No such file or directory)
0.659506 unlink("/home/projectbar/main/cmake/CMakeFiles/mklinks.dir/progress.make.tmp") = -1 ENOENT (No such file or directory)
0.647838 unlink("/home/projectbar/main/test/libyar/YarModels/CMakeFiles/testsuite1_yarmodels.dir/Labels.txt") = -1 ENOENT (No such file or directory)
0.620511 unlink("/home/projectbar/main/test/libyar/YarModels/CMakeFiles/testsuite1_yarmodels.dir/Labels.json") = -1 ENOENT (No such file or directory)
0.601942 unlink("/home/projectbar/main/cmake/CMakeFiles/mklinks.lachesis.dir/Labels.txt") = -1 ENOENT (No such file or directory)
0.591871 access("/home/projectbar/main/src/runbardemo/simple_demo/CMakeFiles", R_OK) = 0
0.582448 write(3, "CMAKE_PROGRESS_1 = \n\n", 21) = 21
0.536947 write(3, "CMAKE_PROGRESS_1 = \n\n", 21) = 21
0.499758 unlink("/home/projectbar/main/test/foo2bar/CMakeFiles/test2.foo2bar.testInputDirectory1.dir/progress.make.tmp") = -1 ENOENT (No such file or directory)
0.458120 unlink("/home/projectbar/main/test/yak2dcs/CMakeFiles/test2.yak2dcs.testsuite2.dir/progress.make.tmp") = -1 ENOENT (No such file or directory)
0.448104 unlink("/home/projectbar/main/test/reportImpressions/CMakeFiles/test2.reportImpressions.dir/progress.make.tmp") = -1 ENOENT (No such file or directory)
0.444344 access("/home/projectbar/main/src/bananas/CMakeFiles/bin.bananas.dir", R_OK) = 0
0.442685 unlink("/home/projectbar/main/test/rvedit/CMakeFiles/test2.rvedit.tefooissingOptionValue.dir/progress.make.tmp") = -1 ENOENT (No such file or directory)
0.425604 unlink("/home/projectbar/main/test/listdcs/CMakeFiles/test2.listdcs.testListCalls5.dir/progress.make.tmp") = -1 ENOENT (No such file or directory)
0.391163 access("/home/projectbar/main/src/siedit/CMakeFiles/siedit.dir", R_OK) = 0
0.362171 access("/home/projectbar/main/test/foo2bar/CMakeFiles/test2.foo2emma.testHowResults6.dir", R_OK) = 0
Note the Ninja generator is much faster (though still not brilliant). For example,
/usr/bin/time -p ninja rebuild_cache
ninja: warning: multiple rules generate ../src/ams2yar/ams2yar. builds involving this target will not be correct; continuing anyway [-w dupbuild=warn] ninja: warning: multiple rules generate ../src/vox/vox. builds involving this target will not be correct; continuing anyway [-w dupbuild=warn] ninja: warning: multiple rules generate ../src/bananas/bananas. builds involving this target will not be correct; continuing anyway [-w dupbuild=warn] ninja: warning: multiple rules generate ../src/fidlertypes2fidlerinfo/fidlertypes2fidlerinfo. builds involving this target will not be correct; continuing anyway [-w dupbuild=warn] ninja: warning: multiple rules generate ../src/mkrundir/mkrundir. builds involving this target will not be correct; continuing anyway [-w dupbuild=warn] ninja: warning: multiple rules generate ../src/runyar/runyar. builds involving this target will not be correct; continuing anyway [-w dupbuild=warn] ninja: warning: multiple rules generate ../src/runyardemo/runyardemo. builds involving this target will not be correct; continuing anyway [-w dupbuild=warn] [1/1] Running CMake to regenerate build system... Generator=Ninja -- FOO_VERSION: 01.02.03 -- Configuring done -- Generating done -- Build files have been written to: /home/project/cmake/build real 12.67 user 1.01 sys 0.31
Note that the project is not quite ready for Ninja yet as there are errors like:
ninja: warning: multiple rules generate ../src/runfoobardemo/runfoobardemo. builds involving this target will not be correct; continuing anyway [-w dupbuild=warn]
and
ninja: error: dependency cycle: ../src/foobar -> ../src/foobar/CMakeFiles/foobar -> ../src/ams2emma/foobar
to be resolved. This question is really about why the Makefile generator is slow. I'm not sure if the problems Ninja shows are useful hints here or red herrings.
Building CMake with more optimisations does not help.
Based on my trace output it and the output of time, it is unlikely that it would. The user time and therefore time spend within the CMake code itself is quite low. (see e.g. What do 'real', 'user' and 'sys' mean in the output of time(1)?).
Here's what I tried for completeness:
export CXX_FLAGS="-O3 -ftree-vectorise -msse2"
cmake -DCMAKE_BUILD_TYPE=RELEASE
Actually using a more optimised CMake does make the configure part faster, but in my case it is the generate part that is slow. It would appear from the timing that this step is somehow I/O bound.
I decided to investigate Florian's idea that using memory insteam of file stream for temporary files might make a difference.
I decided to try the easy route and hacked CMake to write .tmp files to a RAM disk instead.
I then went the whole hog and tried generating the build system on the RAM disk:
sudo mkdir /mnt/ramdisk
sudo mount -t tmpfs -o size=512m tmpfs /mnt/ramdisk
/usr/bin/time -p cmake -H/<source> -B/mnt/ramdisk/build
I was very surprised to find this makes no difference at all to the wall clock time:
real 59.61
user 1.55
sys 0.62
>du -sh /mnt/ramdisk/build/
4.4M /mnt/ramdisk/build/
Similarly with ramfs:
real 51.09
user 1.58
sys 0.50
What could be happening here? I was guessing sub-processes, but I can't work out which sub-processes are consuming the wall clock time if any of them are. They look to be very short lived.
For completeness, here is some output from perf (CMake built with -fno-omit-frame-pointer):
perf record -g --call-graph dwarf cmake -H<source> -B<build>
perf report -g graph
Samples: 17K of event 'cycles', Event count (approx.): 14363392067 Children Self Command Shared Object Symbol + 65.23% 0.00% cmake cmake [.] do_cmake + 65.02% 0.00% cmake cmake [.] cmake::Run + 60.32% 0.00% cmake cmake [.] main + 59.82% 0.00% cmake libc-2.17.so [.] __libc_start_main + 57.78% 0.00% cmake cmake [.] _start + 55.04% 0.00% cmake cmake [.] cmGlobalUnixMakefileGenerator3::Generate + 54.56% 0.00% cmake cmake [.] cmake::Generate + 49.90% 0.00% cmake cmake [.] cmGlobalGenerator::Generate + 38.87% 0.02% cmake cmake [.] cmLocalUnixMakefileGenerator3::Generate + 18.65% 0.01% cmake cmake [.] cmMakefileTargetGenerator::WriteTargetBuildRules + 17.05% 0.02% cmake cmake [.] cmMakefile::ExecuteCommand + 16.99% 0.01% cmake cmake [.] cmMakefile::ReadListFile + 16.84% 0.01% cmake cmake [.] cmCommand::InvokeInitialPass + 16.79% 0.00% cmake cmake [.] cmMakefile::Configure + 14.71% 0.00% cmake cmake [.] cmMakefile::ConfigureSubDirectory + 14.67% 0.05% cmake cmake [.] cmMacroHelperCommand::InvokeInitialPass + 14.27% 0.02% cmake cmake [.] cmMakefileUtilityTargetGenerator::WriteRuleFiles + 13.91% 0.00% cmake cmake [.] cmGlobalGenerator::Configure + 13.50% 0.05% cmake cmake [.] cmOutputConverter::Convert + 13.48% 0.00% cmake cmake [.] cmAddSubDirectoryCommand::InitialPass + 13.46% 0.00% cmake cmake [.] cmMakefile::AddSubDirectory + 12.91% 0.00% cmake cmake [.] cmGlobalUnixMakefileGenerator3::Configure + 12.82% 0.00% cmake cmake [.] cmake::ActualConfigure + 10.90% 0.00% cmake cmake [.] cmake::Configure + 10.55% 0.02% cmake cmake [.] cmMakefileTargetGenerator::WriteObjectRuleFiles + 10.35% 0.09% cmake cmake [.] cmLocalUnixMakefileGenerator3::WriteMakeRule + 9.76% 0.03% cmake cmake [.] cmMakefileTargetGenerator::WriteObjectBuildFile + 7.97% 0.00% cmake cmake [.] cmMakefileLibraryTargetGenerator::WriteRuleFiles + 7.93% 0.00% cmake cmake [.] cmMakefileExecutableTargetGenerator::WriteRuleFiles + 7.88% 0.00% cmake cmake [.] cmLocalUnixMakefileGenerator3::WriteLocalMakefile + 7.68% 0.02% cmake [kernel.kallsyms] [k] sysret_audit + 7.60% 0.05% cmake [kernel.kallsyms] [k] __audit_syscall_exit + 7.40% 0.08% cmake cmake [.] cmsys::SystemTools::CollapseFullPath
And perf report -g graph -no-children:
+ 2.86% cmake libc-2.17.so [.] _int_malloc + 2.15% cmake libc-2.17.so [.] __memcpy_ssse3_back + 2.11% cmake [kernel.kallsyms] [k] find_next_bit + 1.84% cmake libc-2.17.so [.] __memcmp_sse4_1 + 1.83% cmake libc-2.17.so [.] _int_free + 1.71% cmake libstdc++.so.6.0.20 [.] std::__ostream_insert > + 1.18% cmake libstdc++.so.6.0.20 [.] std::basic_string, std::allocator >::~basic_string + 1.13% cmake libc-2.17.so [.] malloc + 1.12% cmake cmake [.] cmOutputConverter::Shell__ArgumentNeedsQuotes + 1.11% cmake libstdc++.so.6.0.20 [.] std::string::compare + 1.08% cmake libc-2.17.so [.] __strlen_sse2_pminub + 1.05% cmake cmake [.] std::string::_S_construct + 1.04% cmake cmake [.] cmsys::SystemTools::ConvertToUnixSlashes + 0.97% cmake cmake [.] yy_get_previous_state + 0.87% cmake cmake [.] cmOutputConverter::Shell__GetArgument + 0.76% cmake libstdc++.so.6.0.20 [.] std::basic_filebuf >::xsputn + 0.75% cmake libstdc++.so.6.0.20 [.] std::string::size + 0.75% cmake cmake [.] cmOutputConverter::Shell__SkipMakeVariables + 0.74% cmake cmake [.] cmOutputConverter::Shell__CharNeedsQuotesOnUnix + 0.73% cmake [kernel.kallsyms] [k] mls_sid_to_context + 0.72% cmake libstdc++.so.6.0.20 [.] std::basic_string, std::allocator >::basic_string + 0.71% cmake cmake [.] cmOutputConverter::Shell__GetArgumentSize + 0.65% cmake libc-2.17.so [.] malloc_consolidate + 0.65% cmake [kernel.kallsyms] [k] mls_compute_context_len + 0.65% cmake cmake [.] cmOutputConverter::Shell__CharNeedsQuotes + 0.64% cmake cmake [.] cmSourceFileLocation::Matches + 0.58% cmake cmake [.] cmMakefile::ExpandVariablesInStringNew + 0.57% cmake cmake [.] std::__deque_buf_size + 0.56% cmake cmake [.] cmCommandArgument_yylex + 0.55% cmake cmake [.] std::vector >::size + 0.54% cmake cmake [.] cmsys::SystemTools::SplitPath + 0.51% cmake libstdc++.so.6.0.20 [.] std::basic_streambuf >::xsputn
有很多方面定义了CMake的配置和生成步骤的持续时间（除了您在CMakeLists.txt文件中实际执行的操作；例如，您的主机系统，您的工具链以及所使用的CMake版本/发行版）。
因此，我尝试着重于您的特定问题。
只是为子目录重建/重写makefile ？
首先：使用add_subdirectory()可以很好地构造CMake代码。但是必须记住，您始终可以在子目录中更改全局CMake属性，并且这些子目录中的目标可能具有交叉依赖性。
那么CMake的作用是什么（考虑到CMakeLists.txt这里讨论的“我触摸了子目录中的一个文件”的情况）：
CMakeLists.txt更改了文件，它将CMakeLists.txt再次遍历文件的完整层次结构，并再次在内存中重建构建环境。cmGeneratedFileStreamBase::Close()）。此行为是必需的，因为即使仅子目录的CMakeLists.txt文件已更改，任何makefile都可以更改，并且已对其进行了优化，以防止在实际make步骤中（通过触摸的makefile）进行不必要的重建。
有什么方法可以加快CMake的生成步骤吗？
因此，是的，它确实会临时重写所有makefile文件（这可能会很慢），并且不，您不能add_subdirectory()仅使用更改后的子目录来将其最小化。
对于CMake自己的代码，将来可能的性能优化之一可能是使用内存流代替临时文件的文件流。
@BruceAdams通过使用RAM磁盘对生成的Makefile环境进行了测试，没有任何效果。
是的，CMake的生成cmake_check_build_system规则做几乎一样的rebuild_cache规则，是用过的-B，-H并--check-build-system选择是CMake的内部命令行选项，因此无证（即使通常称为堆栈溢出，例如，在我的答案之一在这里）。
帮助我加快配置/生成速度的原因在于，它使用比正常发行版更多的优化选项来重建CMake本身，并使用64位工具链而不是当前仍在发行的32位版本。
这是我的Windows PC上始终使用相同的MSYS环境，但使用相同的CMake源代码进行不同的CMake编译的一些测试结果（使用下面的CMake测试脚本以及100个子目录/库）：
CMake 3.2.2官方版本：
$ time -p cmake -G "MSYS Makefiles" ..
[...]
real 43.93
user 0.00
sys 0.03
使用mingw32和GNU 4.8.1我重建CMake 3.2.2与
cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_CXX_FLAGS="-O3" -G "MSYS Makefiles" ..
并得到
$ time -p /c/temp/cmake-3.2.2/MSYS32/bin/cmake.exe -G "MSYS Makefiles" ..
[...]
real 41.37
user 0.01
sys 0.04
并关闭了我的防病毒软件：
$ time -p /c/temp/cmake-3.2.2/MSYS32/bin/cmake.exe -G "MSYS Makefiles" ..
[...]
real 20.98
user 0.00
sys 0.04
使用mingw-w64和GNU 5.3.0我重建CMake 3.2.2与
$ cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_CXX_FLAGS="-march=native -m64 -Ofast -flto" -G "MSYS Makefiles" ..
并得到
$ time -p /c/temp/cmake-3.2.2/MSYS64/bin/cmake.exe -G "MSYS Makefiles" ..
[...]
real 25.59
user 0.00
sys 0.04
并关闭了我的防病毒软件：
$ time -p /c/temp/cmake-3.2.2/MSYS64/bin/cmake.exe -G "MSYS Makefiles" ..
[...]
real 6.95
user 0.00
sys 0.03
总而言之，我看到两个主要影响：
第一个：可以通过选择64位版本并针对您的处理器平台进行优化来加快配置步骤（当然，您必须找到通用的基础-march=...或-mtune=...所有项目的构建PC）。
第二：生成步骤通常可以通过搜索CMake之外的文件I / O瓶颈来加快。就我而言，告诉防病毒软件每次我对它们进行读/写操作时都不要检查工具链并建立目录，这确实在加快速度。
备注：我确认@BruceAdams的测试结果表明，编译器的自动矢量化（默认为-O3或-Ofast）对于CMake源代码在多个进程/多个内核上运行的能力没有太大帮助。
有没有更好的方法来构建CMake项目来实现这一目标？
是的，例如，如果您知道CMake脚本代码的某个子树仅生成一个库且没有依赖性，则可以使用将该部分放入外部项目中ExternalProject_Add()。是的，对于大型CMake项目也有类似的担忧，这被视为良好的“现代CMake”实践（另请参见下面的参考资料）。
参考文献
我用什么来重现你的问题
仅出于完整性考虑，如果有人想对照自己的号码检查这些数字，这是我的测试代码：
cmake_minimum_required(VERSION 3.0)
project(CMakeTest CXX)
#set_property(GLOBAL PROPERTY GLOBAL_DEPENDS_DEBUG_MODE 1)
set(_idx 1)
while (_idx LESS 100)
math(EXPR _next_idx "${_idx} + 1")
if (NOT EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/lib${_idx}")
file(MAKE_DIRECTORY "lib${_idx}")
file(
WRITE "lib${_idx}/lib${_idx}.h"
"int lib${_idx}_func();"
)
file(
WRITE "lib${_idx}/lib${_idx}.cc"
"#include \"lib${_next_idx}.h\"\n"
"int lib${_idx}_func() { return lib${_next_idx}_func(); }"
)
file(
WRITE "lib${_idx}/CMakeLists.txt"
"add_library(lib${_idx} \"lib${_idx}.cc\")\n"
"target_link_libraries(lib${_idx} lib${_next_idx})\n"
"target_include_directories(lib${_idx} PUBLIC \".\")"
)
endif()
add_subdirectory("lib${_idx}")
set(_idx "${_next_idx}")
endwhile()
if (NOT EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/lib${_idx}")
file(MAKE_DIRECTORY "lib${_idx}")
file(
WRITE "lib${_idx}/lib${_idx}.h"
"int lib${_idx}_func();"
)
file(
WRITE "lib${_idx}/lib${_idx}.cc"
"int lib${_idx}_func() { return 0; }"
)
file(
WRITE "lib${_idx}/CMakeLists.txt"
"add_library(lib${_idx} \"lib${_idx}.cc\")\n"
"target_include_directories(lib${_idx} PUBLIC \".\")"
)
endif()
add_subdirectory("lib${_idx}")
if (NOT EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/main.cc")
file(
WRITE "main.cc"
"#include \"lib1.h\"\n"
"int main() { return lib1_func(); }"
)
endif()
add_executable(${PROJECT_NAME} "main.cc")
target_link_libraries(${PROJECT_NAME} lib1)
然后-之后的第一cmake ..和make电话-这样做：
$ touch ../lib100/CMakeLists.txt
$ time -p cmake ..
-- Configuring done
-- Generating done
-- Build files have been written to: [your path here]
real 28.89
user 0.01
sys 0.04
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