[CMake] getting compiler's include paths

Robert Maynard robert.maynard at kitware.com
Wed Jul 3 10:51:45 EDT 2019 

I completely forgot that the Makefiles based generators in CMake have
a separate heuristic for determining system headers.

If you use the Ninja generator I see the expected behavior:
~/W/t/nbuild $ sudo touch /usr/include/c++/7/array
~/W/t/nbuild $ ninja -d explain -v
ninja explain: output test/CMakeFiles/ProjTest.dir/test.cpp.o older
than most recent input /usr/include/c++/7/array (1562165327 vs
1562165329)
ninja explain: test/CMakeFiles/ProjTest.dir/test.cpp.o is dirty
ninja explain: test/ProjTest is dirty
[1/2] /usr/bin/c++   -I../my_lib/include -std=gnu++1z -MD -MT
test/CMakeFiles/ProjTest.dir/test.cpp.o -MF
test/CMakeFiles/ProjTest.dir/test.cpp.o.d -o
test/CMakeFiles/ProjTest.dir/test.cpp.o -c ../test/test.cpp
[2/2] : && /usr/bin/c++     test/CMakeFiles/ProjTest.dir/test.cpp.o
-o test/ProjTest   && :


I will need to spend some more time figuring out the extra include
caching logic for the Makefile based generators, and will report back.

On Thu, Jun 27, 2019 at 8:59 AM jl forums <jlmxyz.forums at gmail.com> wrote:
>
> thanks for the anwer....
> quite not... I'm using cmake 3.14.2 (so, far away from 3.6....) and have a look, in main.cpp, there is #include <filesystem>:
>
> $ find /usr/include/ -name filesystem
> /usr/include/c++/5/experimental/filesystem
> /usr/include/c++/7/experimental/filesystem
> /usr/include/c++/8/filesystem
> /usr/include/c++/8/experimental/filesystem
> $ sudo touch /usr/include/c++/5/experimental/filesystem /usr/include/c++/7/experimental/filesystem /usr/include/c++/8/filesystem /usr/include/c++/8/experimental/filesystem
> $ make
> [100%] Built target FileSync
> $ touch ../main.cxx
> $ make
> Scanning dependencies of target FileSync
> [ 50%] Building CXX object CMakeFiles/FileSync.dir/main.cxx.o
> [100%] Linking CXX executable FileSync
> [100%] Built target FileSync
>
>
> => cmake don't create "full include dependency" which IS a mistake.... updating system g++ can just assume the target is uptodate and in fact just create a broken build...
>
> in cmake cxx.includecache
>
> #IncludeRegexLine: ^[ ]*[#%][ ]*(include|import)[ ]*[<"]([^">]+)([">])
> #IncludeRegexScan: ^.*$
> #IncludeRegexComplain: ^$
> #IncludeRegexTransform:
> /home/orange/crypt/Devel/projets/FileSync/main.cxx
> cstdio
> -
> io.h
> -
> fcntl.h
> -
> locale
> -
> clocale
> -
> fstream
> -
> iostream
> -
> filesystem
> -
>
> $ /usr/bin/gcc-8 -M ../main.cxx
> main.o: ../main.cxx /usr/x86_64-linux-gnu/include/stdc-predef.h \
>  /usr/include/c++/8/cstdio \
>  /usr/include/x86_64-linux-gnu/c++/8/bits/c++config.h \
>  /usr/include/x86_64-linux-gnu/c++/8/bits/os_defines.h \
>  /usr/x86_64-linux-gnu/include/features.h \
>  /usr/x86_64-linux-gnu/include/sys/cdefs.h \
>  /usr/x86_64-linux-gnu/include/bits/wordsize.h \
>  /usr/x86_64-linux-gnu/include/bits/long-double.h \
>  /usr/x86_64-linux-gnu/include/gnu/stubs.h \
>  /usr/x86_64-linux-gnu/include/gnu/stubs-64.h \
>  /usr/include/x86_64-linux-gnu/c++/8/bits/cpu_defines.h \
>  /usr/x86_64-linux-gnu/include/stdio.h \
>  /usr/x86_64-linux-gnu/include/bits/libc-header-start.h \
>  /usr/lib/gcc/x86_64-linux-gnu/8/include/stddef.h \
>  /usr/x86_64-linux-gnu/include/bits/types.h \
>  /usr/x86_64-linux-gnu/include/bits/typesizes.h \
>  /usr/x86_64-linux-gnu/include/bits/types/__FILE.h \
>  /usr/x86_64-linux-gnu/include/bits/types/FILE.h \
>  /usr/x86_64-linux-gnu/include/bits/libio.h \
>  /usr/x86_64-linux-gnu/include/bits/_G_config.h \
>  /usr/x86_64-linux-gnu/include/bits/types/__mbstate_t.h \
>  /usr/lib/gcc/x86_64-linux-gnu/8/include/stdarg.h \
>  /usr/x86_64-linux-gnu/include/bits/stdio_lim.h \
>  /usr/x86_64-linux-gnu/include/bits/sys_errlist.h \
>  /usr/include/c++/8/locale /usr/include/c++/8/bits/localefwd.h \
>  /usr/include/x86_64-linux-gnu/c++/8/bits/c++locale.h \
>  /usr/include/c++/8/clocale /usr/x86_64-linux-gnu/include/locale.h \
>  /usr/x86_64-linux-gnu/include/bits/locale.h \
>  /usr/x86_64-linux-gnu/include/bits/types/locale_t.h \
>  /usr/x86_64-linux-gnu/include/bits/types/__locale_t.h \
>  /usr/include/c++/8/iosfwd /usr/include/c++/8/bits/stringfwd.h \
>  /usr/include/c++/8/bits/memoryfwd.h /usr/include/c++/8/bits/postypes.h \
>  /usr/include/c++/8/cwchar /usr/x86_64-linux-gnu/include/wchar.h \
>  /usr/x86_64-linux-gnu/include/bits/floatn.h \
>  /usr/x86_64-linux-gnu/include/bits/floatn-common.h \
>  /usr/x86_64-linux-gnu/include/bits/wchar.h \
>  /usr/x86_64-linux-gnu/include/bits/types/wint_t.h \
>  /usr/x86_64-linux-gnu/include/bits/types/mbstate_t.h \
>  /usr/include/c++/8/cctype /usr/x86_64-linux-gnu/include/ctype.h \
>  /usr/x86_64-linux-gnu/include/endian.h \
>  /usr/x86_64-linux-gnu/include/bits/endian.h \
>  /usr/x86_64-linux-gnu/include/bits/byteswap.h \
>  /usr/x86_64-linux-gnu/include/bits/byteswap-16.h \
>  /usr/x86_64-linux-gnu/include/bits/uintn-identity.h \
>  /usr/include/c++/8/bits/locale_classes.h /usr/include/c++/8/string \
>  /usr/include/c++/8/bits/char_traits.h \
>  /usr/include/c++/8/bits/stl_algobase.h \
>  /usr/include/c++/8/bits/functexcept.h \
>  /usr/include/c++/8/bits/exception_defines.h \
>  /usr/include/c++/8/bits/cpp_type_traits.h \
>  /usr/include/c++/8/ext/type_traits.h \
>  /usr/include/c++/8/ext/numeric_traits.h \
>  /usr/include/c++/8/bits/stl_pair.h /usr/include/c++/8/bits/move.h \
>  /usr/include/c++/8/bits/concept_check.h /usr/include/c++/8/type_traits \
>  /usr/include/c++/8/bits/stl_iterator_base_types.h \
>  /usr/include/c++/8/bits/stl_iterator_base_funcs.h \
>  /usr/include/c++/8/debug/assertions.h \
>  /usr/include/c++/8/bits/stl_iterator.h \
>  /usr/include/c++/8/bits/ptr_traits.h /usr/include/c++/8/debug/debug.h \
>  /usr/include/c++/8/bits/predefined_ops.h /usr/include/c++/8/cstdint \
>  /usr/lib/gcc/x86_64-linux-gnu/8/include/stdint.h \
>  /usr/x86_64-linux-gnu/include/stdint.h \
>  /usr/x86_64-linux-gnu/include/bits/stdint-intn.h \
>  /usr/x86_64-linux-gnu/include/bits/stdint-uintn.h \
>  /usr/include/c++/8/bits/allocator.h \
>  /usr/include/x86_64-linux-gnu/c++/8/bits/c++allocator.h \
>  /usr/include/c++/8/ext/new_allocator.h /usr/include/c++/8/new \
>  /usr/include/c++/8/exception /usr/include/c++/8/bits/exception.h \
>  /usr/include/c++/8/bits/exception_ptr.h \
>  /usr/include/c++/8/bits/cxxabi_init_exception.h \
>  /usr/include/c++/8/typeinfo /usr/include/c++/8/bits/hash_bytes.h \
>  /usr/include/c++/8/bits/nested_exception.h \
>  /usr/include/c++/8/bits/ostream_insert.h \
>  /usr/include/c++/8/bits/cxxabi_forced.h \
>  /usr/include/c++/8/bits/stl_function.h \
>  /usr/include/c++/8/backward/binders.h \
>  /usr/include/c++/8/bits/range_access.h \
>  /usr/include/c++/8/initializer_list \
>  /usr/include/c++/8/bits/basic_string.h \
>  /usr/include/c++/8/ext/atomicity.h \
>  /usr/include/x86_64-linux-gnu/c++/8/bits/gthr.h \
>  /usr/include/x86_64-linux-gnu/c++/8/bits/gthr-default.h \
>  /usr/x86_64-linux-gnu/include/pthread.h \
>  /usr/x86_64-linux-gnu/include/sched.h \
>  /usr/x86_64-linux-gnu/include/bits/types/time_t.h \
>  /usr/x86_64-linux-gnu/include/bits/types/struct_timespec.h \
>  /usr/x86_64-linux-gnu/include/bits/sched.h \
>  /usr/x86_64-linux-gnu/include/bits/cpu-set.h \
>  /usr/x86_64-linux-gnu/include/time.h \
>  /usr/x86_64-linux-gnu/include/bits/time.h \
>  /usr/x86_64-linux-gnu/include/bits/timex.h \
>  /usr/x86_64-linux-gnu/include/bits/types/struct_timeval.h \
>  /usr/x86_64-linux-gnu/include/bits/types/clock_t.h \
>  /usr/x86_64-linux-gnu/include/bits/types/struct_tm.h \
>  /usr/x86_64-linux-gnu/include/bits/types/clockid_t.h \
>  /usr/x86_64-linux-gnu/include/bits/types/timer_t.h \
>  /usr/x86_64-linux-gnu/include/bits/types/struct_itimerspec.h \
>  /usr/x86_64-linux-gnu/include/bits/pthreadtypes.h \
>  /usr/x86_64-linux-gnu/include/bits/thread-shared-types.h \
>  /usr/x86_64-linux-gnu/include/bits/pthreadtypes-arch.h \
>  /usr/x86_64-linux-gnu/include/bits/setjmp.h \
>  /usr/include/x86_64-linux-gnu/c++/8/bits/atomic_word.h \
>  /usr/include/c++/8/ext/alloc_traits.h \
>  /usr/include/c++/8/bits/alloc_traits.h \
>  /usr/include/c++/8/ext/string_conversions.h /usr/include/c++/8/cstdlib \
>  /usr/x86_64-linux-gnu/include/stdlib.h \
>  /usr/x86_64-linux-gnu/include/bits/waitflags.h \
>  /usr/x86_64-linux-gnu/include/bits/waitstatus.h \
>  /usr/x86_64-linux-gnu/include/sys/types.h \
>  /usr/x86_64-linux-gnu/include/sys/select.h \
>  /usr/x86_64-linux-gnu/include/bits/select.h \
>  /usr/x86_64-linux-gnu/include/bits/types/sigset_t.h \
>  /usr/x86_64-linux-gnu/include/bits/types/__sigset_t.h \
>  /usr/x86_64-linux-gnu/include/sys/sysmacros.h \
>  /usr/x86_64-linux-gnu/include/bits/sysmacros.h \
>  /usr/x86_64-linux-gnu/include/alloca.h \
>  /usr/x86_64-linux-gnu/include/bits/stdlib-float.h \
>  /usr/include/c++/8/bits/std_abs.h /usr/include/c++/8/cerrno \
>  /usr/x86_64-linux-gnu/include/errno.h \
>  /usr/x86_64-linux-gnu/include/bits/errno.h \
>  /usr/x86_64-linux-gnu/include/linux/errno.h \
>  /usr/x86_64-linux-gnu/include/asm/errno.h \
>  /usr/x86_64-linux-gnu/include/asm-generic/errno.h \
>  /usr/x86_64-linux-gnu/include/asm-generic/errno-base.h \
>  /usr/include/c++/8/bits/functional_hash.h \
>  /usr/include/c++/8/bits/basic_string.tcc \
>  /usr/include/c++/8/bits/locale_classes.tcc \
>  /usr/include/c++/8/bits/locale_facets.h /usr/include/c++/8/cwctype \
>  /usr/x86_64-linux-gnu/include/wctype.h \
>  /usr/x86_64-linux-gnu/include/bits/wctype-wchar.h \
>  /usr/include/x86_64-linux-gnu/c++/8/bits/ctype_base.h \
>  /usr/include/c++/8/bits/ios_base.h /usr/include/c++/8/system_error \
>  /usr/include/x86_64-linux-gnu/c++/8/bits/error_constants.h \
>  /usr/include/c++/8/stdexcept /usr/include/c++/8/streambuf \
>  /usr/include/c++/8/bits/streambuf.tcc \
>  /usr/include/c++/8/bits/streambuf_iterator.h \
>  /usr/include/x86_64-linux-gnu/c++/8/bits/ctype_inline.h \
>  /usr/include/c++/8/bits/locale_facets.tcc \
>  /usr/include/c++/8/bits/locale_facets_nonio.h /usr/include/c++/8/ctime \
>  /usr/include/x86_64-linux-gnu/c++/8/bits/time_members.h \
>  /usr/include/x86_64-linux-gnu/c++/8/bits/messages_members.h \
>  /usr/x86_64-linux-gnu/include/libintl.h \
>  /usr/include/c++/8/bits/codecvt.h \
>  /usr/include/c++/8/bits/locale_facets_nonio.tcc \
>  /usr/include/c++/8/bits/locale_conv.h \
>  /usr/include/c++/8/bits/unique_ptr.h /usr/include/c++/8/utility \
>  /usr/include/c++/8/bits/stl_relops.h /usr/include/c++/8/tuple \
>  /usr/include/c++/8/array /usr/include/c++/8/bits/uses_allocator.h \
>  /usr/include/c++/8/bits/invoke.h /usr/include/c++/8/fstream \
>  /usr/include/c++/8/istream /usr/include/c++/8/ios \
>  /usr/include/c++/8/bits/basic_ios.h \
>  /usr/include/c++/8/bits/basic_ios.tcc /usr/include/c++/8/ostream \
>  /usr/include/c++/8/bits/ostream.tcc /usr/include/c++/8/bits/istream.tcc \
>  /usr/include/x86_64-linux-gnu/c++/8/bits/basic_file.h \
>  /usr/include/x86_64-linux-gnu/c++/8/bits/c++io.h \
>  /usr/include/c++/8/bits/fstream.tcc /usr/include/c++/8/iostream \
>  /usr/include/c++/8/filesystem
>
>
> amazing, no? cmake find only 9 dependencies against 100+ real ones (and I don't even speak of errors that can be caused in parsing if some -D option is changed....
>
> thanks and regards
> JLM
>
>
> Le lun. 24 juin 2019 à 14:14, Robert Maynard <robert.maynard at kitware.com> a écrit :
>>
>> It look that starting with CMake 3.6 modification of system headers
>> will cause CMake to recompile projects. What version of CMake and your
>> compiler are you using?
>>
>> On Mon, Jun 17, 2019 at 9:40 AM jl forums <jlmxyz.forums at gmail.com> wrote:
>> >
>> > Hi,
>> > I want to create a full tag file and for this require to know the compiler full include path...  there is a way to had custom includes path but didn't found any variables for the include path....
>> > for example :
>> > $ gcc-8 -v -x c -E /dev/null
>> > Using built-in specs.
>> > [....]
>> > ignoring nonexistent directory "/usr/local/include/x86_64-linux-gnu"
>> > #include "..." search starts here:
>> > #include <...> search starts here:
>> >  /usr/lib/gcc/x86_64-linux-gnu/8/include
>> >  /usr/local/include
>> >  /usr/lib/gcc/x86_64-linux-gnu/8/include-fixed
>> >  /usr/x86_64-linux-gnu/include
>> >  /usr/include/x86_64-linux-gnu
>> >  /usr/include
>> > End of search list.
>> > [...]
>> >
>> > $ gcc -v -x c -E /dev/null
>> > Using built-in specs.
>> > [...]
>> > ignoring nonexistent directory "/usr/local/include/x86_64-linux-gnu"
>> > #include "..." search starts here:
>> > #include <...> search starts here:
>> >  /usr/lib/gcc/x86_64-linux-gnu/7/include
>> >  /usr/local/include
>> >  /usr/lib/gcc/x86_64-linux-gnu/7/include-fixed
>> >  /usr/x86_64-linux-gnu/include
>> >  /usr/include/x86_64-linux-gnu
>> >  /usr/include
>> > End of search list.
>> > [...]
>> >
>> > I tried to
>> >
>> >
>> > get_target_property(moggle_interface_includes FileSync INTERFACE_INCLUDE_DIRECTORIES)
>> > message("Moggle interface includes: ${moggle_interface_includes}")
>> >
>> > get_target_property(motor_includes FileSync INCLUDE_DIRECTORIES)
>> > message("MOTOR includes ${motor_includes}")
>> >
>> > but I get
>> >
>> > Moggle interface includes: moggle_interface_includes-NOTFOUND
>> > MOTOR includes motor_includes-NOTFOUND
>> >
>> >
>> > there is also some issue because cmake strip dependencies from system's include, which means that updating a system software won't cause rebuild and consider that the build is uptodate, causing unexpected results
>> > seems that there is ways to workaround this :  https://stackoverflow.com/questions/7461000/handling-header-files-dependencies-with-cmake but this is ugly... would be better to let the user choose with an option
>> >
>> > thanks and regards
>> > JLM
>> > --
>> >
>> > Powered by www.kitware.com
>> >
>> > Please keep messages on-topic and check the CMake FAQ at: http://www.cmake.org/Wiki/CMake_FAQ
>> >
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>> >
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