[Buildroot] [Bug 13241] New: CMake miss linking with pthread library

[Buildroot] [Bug 13241] New: CMake miss linking with pthread library

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=13241

            Bug ID: 13241
           Summary: CMake miss linking with pthread library
           Product: buildroot
           Version: unspecified
          Hardware: All
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P5
         Component: Other
          Assignee: unassigned at buildroot.uclibc.org
          Reporter: leo at yuriev.ru
                CC: buildroot at uclibc.org
  Target Milestone: ---

When testing my package, I found a series of similar problems when building
(current master branch) for some platforms.

For instance:
$ utils/test-pkg -k -a -p libmdbx
                             andes-nds32 [ 1/45]: FAILED
                             arm-aarch64 [ 2/45]: FAILED
                    bootlin-x86-64-glibc [ 3/45]: FAILED
                        br-aarch64-glibc [ 4/45]: FAILED
                           br-arcle-hs38 [ 5/45]: OK
                            br-arm-basic [ 6/45]: OK
                  br-arm-cortex-a9-glibc [ 7/45]: FAILED
                   br-arm-cortex-a9-musl [ 8/45]: OK
                   br-arm-cortex-m4-full [ 9/45]: SKIPPED
                             br-arm-full [10/45]: OK
                    br-arm-full-nothread [11/45]: SKIPPED
                      br-arm-full-static [12/45]: OK
                   br-i386-pentium4-full [13/45]: OK
                br-i386-pentium-mmx-musl [14/45]: OK
                       br-m68k-5208-full [15/45]: SKIPPED
                      br-m68k-68040-full [16/45]: OK
                    br-microblazeel-full [17/45]: FAILED
                 br-mips32r6-el-hf-glibc [18/45]: FAILED
                      br-mips64-n64-full [19/45]: OK
                 br-mips64r6-el-hf-glibc [20/45]: FAILED
                      br-mipsel-o32-full [21/45]: OK
                          br-nios2-glibc [22/45]: FAILED
                      br-openrisc-uclibc [23/45]: OK
               br-powerpc-603e-basic-cpp [24/45]: OK
             br-powerpc64le-power8-glibc [25/45]: FAILED
               br-powerpc64-power7-glibc [26/45]: FAILED
                  br-powerpc-e500mc-full [27/45]: OK
                              br-riscv32 [28/45]: FAILED
                              br-riscv64 [29/45]: FAILED
                         br-riscv64-musl [30/45]: OK
                             br-sh4-full [31/45]: OK
                        br-sparc64-glibc [32/45]: FAILED
                         br-sparc-uclibc [33/45]: SKIPPED
                    br-x86-64-core2-full [34/45]: OK
                          br-x86-64-musl [35/45]: OK
                          br-xtensa-full [36/45]: OK
                       linaro-aarch64-be [37/45]: FAILED
                          linaro-aarch64 [38/45]: FAILED
                              linaro-arm [39/45]: FAILED
                     sourcery-arm-armv4t [40/45]: FAILED
                            sourcery-arm [41/45]: FAILED
                     sourcery-arm-thumb2 [42/45]: FAILED
                         sourcery-mips64 [43/45]: FAILED
                           sourcery-mips [44/45]: FAILED
                          sourcery-nios2 [45/45]: FAILED
45 builds, 4 skipped, 23 build failed, 0 legal-info failed

The reason is that CMake doesn't link executables and so-libraries with the
pthread library and doesn't use the '-pthread' flag either.
Digging a little deeper, I saw that the build always breaks when the code of
pthread's functions is in the separate library, i.e. when the libpthread should
be linked explicitly.

I observe this behavior with cmake 3.17.4 on Fedora 32 and with cmake 3.16.3 on
Ubuntu 20.04.
At the same time, I am sure that everything is correct in my CMakefiles.
In particular, when building locally for a host system, I see the `-pthread`
flag in the linking commands (or linking with a libpthread on the other host).

--

I looked at support/misc/toolchainfile.cmake.in and package/pkg-cmake.mk but I
didn't notice any errors.
As a workaround, I temporarily added a patch to my package that forcibly adds
the `-pthread` flag for linking executables and so-libraries.
https://github.com/erthink/libmdbx/commit/787eaaa373073e17f3a53658b085c255bc2c8ff8

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[Buildroot] [Bug 13241] CMake miss linking with pthread library

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=13241

--- Comment #1 from Fabrice Fontaine <fontaine.fabrice@gmail.com> ---
Can you attach your patch that adds libmdbx package (i.e. Config.in, libmdbx.mk
and libmdbx.hash)?

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[Buildroot] [Bug 13241] CMake miss linking with pthread library

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=13241

--- Comment #2 from Leonid Yuriev <leo@yuriev.ru> ---
Created attachment 8601
  --> https://bugs.busybox.net/attachment.cgi?id=8601&action=edit
patch with libmdbx package as a testcase

Basically this is identical to patch with libmdbx-package submission,
but WITHOUT workaround for https://bugs.busybox.net/show_bug.cgi?id=13241

So it could be used as a testcase.

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[Buildroot] [Bug 13241] CMake miss linking with pthread library

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=13241

--- Comment #3 from Fabrice Fontaine <fontaine.fabrice@gmail.com> ---
I build-tested v4 (i.e.
https://patchwork.ozlabs.org/project/buildroot/patch/20201006192709.8265-2-leo at yuriev.ru/mbox/)
and every configuration is building fine with cmake 3.18.2.

I also tried to build test it with host-cmake (i.e cmake 3.15.5) and it also
seems to build fine so I don't know if there is anything that could be done on
buildroot side.

You can send a v5 with your workaround or we can also wait to see if there is
any autobuilder failures after v4 is merged.

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[Buildroot] [Bug 13241] CMake miss linking with pthread library

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=13241

--- Comment #4 from Leonid Yuriev <leo@yuriev.ru> ---
(In reply to Fabrice Fontaine from comment #3)

Minor clarification:

- v4 of the my package-submission patch already includes a workaround for this
bug. So it is expected to build it with CMake >= 3.8 successfully with
buildroot or on a host.

- To reproduce the problem, remove the corresponding patch from the libmdbx
package, or use the patch attached (#8601) above without workaround.

- v4 passes review and libmdbx' mainstream already contain a workaround for
this bug. So I don't suppose to ship v5 until the next release of libmdbx or
until some bug affecting buildroot users or builds was fixed.

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