error: flexible array member not at end of struct

[wcohen]

I looks like the Fedora rawhide gcc-12.2.1-1.fc38.x86_64 is picker than earlier compilers (gcc-12.1.1-3.fc37.1) about where variable length fields are in structures. rr compiled with gcc-12.1.1-3.fc37 compiled but when trying to compile a updated git checkout of rr on Fedora rawhide with the newer compiler got the following error:

/usr/bin/g++ -DEXECINFO_H=1 -DFANOTIFY_H=1 -DMQUEUE_H=1 -DPROC_SERVICE_H=1 -DRR_VERSION=\"5.6.0\" -Drr_EXPORTS -I/home/wcohen/rpmbuild/BUILD/rr-fc63ee66416c31b2588b07e1d7f0b083de0ae51f/include -I/home/wcohen/rpmbuild/BUILD/rr-fc63ee66416c31b2588b07e1d7f0b083de0ae51f/third-party/proc-service -I/home/wcohen/rpmbuild/BUILD/rr-fc63ee66416c31b2588b07e1d7f0b083de0ae51f/third-party/brotli/include -I/home/wcohen/rpmbuild/BUILD/rr-fc63ee66416c31b2588b07e1d7f0b083de0ae51f/redhat-linux-build -O2 -flto=auto -ffat-lto-objects -fexceptions -g -grecord-gcc-switches -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -Wp,-D_GLIBCXX_ASSERTIONS -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -fstack-protector-strong -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1  -m64  -mtune=generic -fasynchronous-unwind-tables -fstack-clash-protection -fcf-protection -D__USE_LARGEFILE64 -pthread -msse2 -D__MMX__ -D__SSE__ -D__SSE2__ -fmacro-prefix-map=/home/wcohen/rpmbuild/BUILD/rr-fc63ee66416c31b2588b07e1d7f0b083de0ae51f/= -D__STDC_LIMIT_MACROS -D__STDC_FORMAT_MACROS -std=c++14  -pthread  -DNDEBUG -Wall -Wextra -UDEBUG -DNDEBUG -g3 -flto -MD -MT CMakeFiles/rr.dir/src/record_syscall.cc.o -MF CMakeFiles/rr.dir/src/record_syscall.cc.o.d -o CMakeFiles/rr.dir/src/record_syscall.cc.o -c /home/wcohen/rpmbuild/BUILD/rr-fc63ee66416c31b2588b07e1d7f0b083de0ae51f/src/record_syscall.cc
In file included from /home/wcohen/rpmbuild/BUILD/rr-fc63ee66416c31b2588b07e1d7f0b083de0ae51f/src/record_syscall.cc:12:
/home/wcohen/rpmbuild/BUILD/rr-fc63ee66416c31b2588b07e1d7f0b083de0ae51f/src/record_syscall.cc: In instantiation of 'struct rr::get_ethtool_gstrings_arch<X86Arch>(RecordTask*)::SingleStringSet':
/home/wcohen/rpmbuild/BUILD/rr-fc63ee66416c31b2588b07e1d7f0b083de0ae51f/src/record_syscall.cc:1456:3:   required from 'void rr::get_ethtool_gstrings_arch(RecordTask*) [with Arch = X86Arch]'
/home/wcohen/rpmbuild/BUILD/rr-fc63ee66416c31b2588b07e1d7f0b083de0ae51f/src/record_syscall.cc:1486:3:   required from here
/usr/include/linux/ethtool.h:778:17: error: flexible array member 'ethtool_sset_info::data' not at end of 'struct rr::get_ethtool_gstrings_arch<X86Arch>(RecordTask*)::SingleStringSet'
  778 |         __u32   data[];
      |                 ^~~~
/home/wcohen/rpmbuild/BUILD/rr-fc63ee66416c31b2588b07e1d7f0b083de0ae51f/src/record_syscall.cc:1455:14: note: next member 'uint32_t rr::get_ethtool_gstrings_arch<X86Arch>(RecordTask*)::SingleStringSet::data' declared here
 1455 |     uint32_t data;
      |              ^~~~
/home/wcohen/rpmbuild/BUILD/rr-fc63ee66416c31b2588b07e1d7f0b083de0ae51f/src/record_syscall.cc:1453:10: note: in the definition of 'struct rr::get_ethtool_gstrings_arch<X86Arch>(RecordTask*)::SingleStringSet'
 1453 |   struct SingleStringSet {
      |          ^~~~~~~~~~~~~~~
/home/wcohen/rpmbuild/BUILD/rr-fc63ee66416c31b2588b07e1d7f0b083de0ae51f/src/record_syscall.cc: In instantiation of 'struct rr::get_ethtool_gstrings_arch<X64Arch>(RecordTask*)::SingleStringSet':
/home/wcohen/rpmbuild/BUILD/rr-fc63ee66416c31b2588b07e1d7f0b083de0ae51f/src/record_syscall.cc:1456:3:   required from 'void rr::get_ethtool_gstrings_arch(RecordTask*) [with Arch = X64Arch]'
/home/wcohen/rpmbuild/BUILD/rr-fc63ee66416c31b2588b07e1d7f0b083de0ae51f/src/record_syscall.cc:1486:3:   required from here
/usr/include/linux/ethtool.h:778:17: error: flexible array member 'ethtool_sset_info::data' not at end of 'struct rr::get_ethtool_gstrings_arch<X64Arch>(RecordTask*)::SingleStringSet'
  778 |         __u32   data[];
      |                 ^~~~
/home/wcohen/rpmbuild/BUILD/rr-fc63ee66416c31b2588b07e1d7f0b083de0ae51f/src/record_syscall.cc:1455:14: note: next member 'uint32_t rr::get_ethtool_gstrings_arch<X64Arch>(RecordTask*)::SingleStringSet::data' declared here
 1455 |     uint32_t data;
      |              ^~~~
/home/wcohen/rpmbuild/BUILD/rr-fc63ee66416c31b2588b07e1d7f0b083de0ae51f/src/record_syscall.cc:1453:10: note: in the definition of 'struct rr::get_ethtool_gstrings_arch<X64Arch>(RecordTask*)::SingleStringSet'
 1453 |   struct SingleStringSet {
      |          ^~~~~~~~~~~~~~~
/home/wcohen/rpmbuild/BUILD/rr-fc63ee66416c31b2588b07e1d7f0b083de0ae51f/src/record_syscall.cc: In instantiation of 'struct rr::get_ethtool_gstrings_arch<ARM64Arch>(RecordTask*)::SingleStringSet':
/home/wcohen/rpmbuild/BUILD/rr-fc63ee66416c31b2588b07e1d7f0b083de0ae51f/src/record_syscall.cc:1456:3:   required from 'void rr::get_ethtool_gstrings_arch(RecordTask*) [with Arch = ARM64Arch]'
/home/wcohen/rpmbuild/BUILD/rr-fc63ee66416c31b2588b07e1d7f0b083de0ae51f/src/record_syscall.cc:1486:3:   required from here
/usr/include/linux/ethtool.h:778:17: error: flexible array member 'ethtool_sset_info::data' not at end of 'struct rr::get_ethtool_gstrings_arch<ARM64Arch>(RecordTask*)::SingleStringSet'
  778 |         __u32   data[];
      |                 ^~~~
/home/wcohen/rpmbuild/BUILD/rr-fc63ee66416c31b2588b07e1d7f0b083de0ae51f/src/record_syscall.cc:1455:14: note: next member 'uint32_t rr::get_ethtool_gstrings_arch<ARM64Arch>(RecordTask*)::SingleStringSet::data' declared here
 1455 |     uint32_t data;
      |              ^~~~
/home/wcohen/rpmbuild/BUILD/rr-fc63ee66416c31b2588b07e1d7f0b083de0ae51f/src/record_syscall.cc:1453:10: note: in the definition of 'struct rr::get_ethtool_gstrings_arch<ARM64Arch>(RecordTask*)::SingleStringSet'
 1453 |   struct SingleStringSet {
      |          ^~~~~~~~~~~~~~~
gmake[2]: *** [CMakeFiles/rr.dir/build.make:744: CMakeFiles/rr.dir/src/record_syscall.cc.o] Error 1
gmake[2]: Leaving directory '/home/wcohen/rpmbuild/BUILD/rr-fc63ee66416c31b2588b07e1d7f0b083de0ae51f/redhat-linux-build'
gmake[1]: *** [CMakeFiles/Makefile2:1468: CMakeFiles/rr.dir/all] Error 2
gmake[1]: Leaving directory '/home/wcohen/rpmbuild/BUILD/rr-fc63ee66416c31b2588b07e1d7f0b083de0ae51f/redhat-linux-build'
gmake: *** [Makefile:169: all] Error 2

[vcunat]

For reference, the cause wasn't update of gcc but kernel headers: torvalds/linux@94dfc73