On 15/9/20 4:31 pm, Sebastian Huber wrote: > On 15/09/2020 00:46, Chris Johns wrote: > >> On 15/9/20 1:18 am, Sebastian Huber wrote: >>> Hello Christian, >>> >>> On 14/09/2020 14:23, Christian Mauderer wrote: >>>> Hello Sebastian, >>>> >>>> I get a linker error when I try to build libbsd for BBB (with a buildset >>>> that >>>> builds everything but netipsec): >>>> >>>> ----- >>>> /home/EB/christian_m/Projekte/rtems-bbb/install/rtems/6/lib/gcc/arm-rtems6/10.2.1/../../../../arm-rtems6/bin/ld: >>>> >>>> ./libbsd.a(uipc_mbuf.c.20.o): in function `m_unmappedtouio': >>>> /home/EB/christian_m/Projekte/rtems-bbb/libs/rtems-libbsd/build/arm-rtems6-beagleboneblack-noIPSec/../../freebsd/sys/kern/uipc_mbuf.c:1813: >>>> >>>> undefined reference to `PHYS_TO_VM_PAGE' >>>> /home/EB/christian_m/Projekte/rtems-bbb/install/rtems/6/lib/gcc/arm-rtems6/10.2.1/../../../../arm-rtems6/bin/ld: >>>> >>>> /home/EB/christian_m/Projekte/rtems-bbb/libs/rtems-libbsd/build/arm-rtems6-beagleboneblack-noIPSec/../../freebsd/sys/kern/uipc_mbuf.c:1814: >>>> >>>> undefined reference to `uiomove_fromphys' >>>> collect2: error: ld returned 1 exit status >>>> ----- >>>> >>>> Configure line for libbsd is: >>>> >>>> ./waf configure \ >>>> >>>> --prefix=/home/EB/christian_m/Projekte/rtems-bbb//install/rtems/6 \ >>>> --rtems-bsps=arm/beagleboneblack \ >>>> >>>> --buildset=/home/EB/christian_m/Projekte/rtems-bbb//build/src/noipsec.ini \ >>>> --enable-warnings \ >>>> --optimization=2 \ >>>> --rtems-version=6 >>>> >>>> Adding your patch from ages ago to libbsd works to solve that: >>>> >>>> >>>> https://gitlab.com/c-mauderer/rtems-libbsd/-/commit/c9474c0b228d91dff098d617234842d56af3c4d7.patch >>>> >>>> >>>> >>>> But you haven't applied it to the libbsd master. So I assume that there is >>>> a >>>> better workaround for that problem? What's the correct solution? >>> thanks for testing. Apparently, I tested with this patch applied. This is an >>> open issue. Chris was not happy with this patch. >> Yes that is correct. Patching libbsd this way solves the issue for us, the >> RTEMS >> developers, however the same problem remains for applications linking to >> libbsd. > > No, we have two different kind of flags which play a role here: > > 1. Flags for the compiler: -fdata-sections -ffunction-sections > > 2. A flag for the linker: -Wl,--gc-sections > > I linker flag is required by the application if it links to -lbsd. The > compiler > flags are required to build libbsd itself, but they are NOT required to build > the application objects or other libraries.
Thanks, this makes sense. We still need to address the exporting of the link flag. waf_libbsd.py is not the place for the flags. This should be added to libbsd.py in the defaults. waf_libbsd.py is part of build engine and should not have any settings. I can have a look after my posted changes are pushed. The self.data in waf_libbsd.py is a bit of a beast these days. > The linker flag part of the patch could be removed. It just makes libbsd > requirements a bit more explicit. Let me have a look at this. Thinking about this now we also need to indicate if the "flag" is to be exported. The section compilers do not but the link option does. >> Requiring users copy these flags into application specific build systems is >> fragile. Just look at the issues EPICS has updating to RTEMS 5. We need to >> do a >> better of job of handling these settings. As a result I do not support the >> easy fix. >> >>> I think the -fdata-sections and -ffunction-sections flags should not be >>> exported >>> by the pkg-config file of the build system since these are optimization >>> flags >>> which affect the code generation. However, for libbsd these flags are >>> mandatory >>> and should be enforced by a library-specific rule. >> I am not sure what you mean when you say .. enforcing a library specific >> rule? >> We can only lead by providing robust interfaces that do not change with each >> version of RTEMS yet let us evolve RTEMS. >> >> I believe rtems.git needs to export flags for libraries we use via pkgconfig. >> For example we could use variables for this: >> >> pkgconfig /somewhere/i386-rtems6-pc686.pc --variable libbsd-cflags > To use a library, you don't need CFLAGS. You need LDFLAGS and maybe CPPFLAGS > if > it has special include paths. Depends on the include paths used and this means the prefix. If there are no special flags pkg-config will return an empty string. >> The variable name `libbsd-cflags` could be something less specific to libbsd >> like `sections-cflags` or something better. We can have other variables like >> a >> base address, a u-boot mkimage set of flags, etc. I would like to see these >> grow >> over time to address the difficult area of exporting architecture and BSP >> specific settings. > Yes, I also think that pkg-config should be the interface for applications to > get these values. Great. >> >> LibBSD can then create and install it's own .pc file: >> >> $ cat /opt/rtems/6/lib/pkgconfig/bsd.pc >> prefix=/opt/rtems/6 >> exec_prefix=/opt/rtems/6 >> libdir=/opt/tems/6/lib >> includedir=/opt/rtems/6/include >> >> Name: libbsd >> Version: 5.1.0 >> Description: RTEMS LibBSD >> URL: httpis:/git.rtems.org/rtems-libbsd.git >> Libs: -lbsd >> Cflags: -fdata-sections -ffunction-sections >> >> An application can then: >> >> $ pkg-config /opt/rtems/6/lib/pkgconfig/i386-rtems6-pc686.pc --cflags --libs >> bsd >> -qrtems -B/opt/rtems/6/i386-rtems6/lib/ -B/opt/rtems/6/i386-rtems6/pc686/lib/ >> --specs bsp_specs -mtune=pentiumpro -march=pentium -O2 -g -ffunction-sections >> -Wnested-externs -fdata-sections -ffunction-sections -lbsd >> >> I am sure the .pc files could be better than the quick hack shown here. I >> think >> a suitable design and model could be established that can be used for all 3rd >> party libraries. >> >> Note, rtems_waf has been using .pc files for years waiting for the RTEMS .pc >> support to evolve into a copmlete interface ... >> >> https://git.rtems.org/rtems_waf/tree/rtems.py#n794 > > Yes, the libbsd could install its own pkg-config file although using an > installed libbsd is pretty simple. You just have to add -lbsd and > -Wl,--gc-sections. The -Wl,--gc-sections is already provided by the BSP > pkg-config file. Pretty simple is relative. A pkg-config file removes the needs to update these flags if something changes. I would rather see us have files for all libraries even if they are simple. This way the simple and hard are all handled the same way. Chris _______________________________________________ devel mailing list devel@rtems.org http://lists.rtems.org/mailman/listinfo/devel
