Compile error in Fedora 28: strncpy’ specified bound equals destination size

[dioni21]

System information

Type	Version/Name
Distribution Name	Fedora
Distribution Version	28
Linux Kernel	4.17.12-200.fc28.x86_64
Architecture	x86_64
ZFS Version	commit 55972a6
SPL Version	XXX

Describe the problem you're observing

Error compiling the current master on Fedora 28. It worked on Fedora 27

I suspect Fedora 28 has enabled by default stricter compile verification.

Describe how to reproduce the problem

git checkout master
./autogen.sh && ./configure --enable-debuginfo --enable-silent-rules --enable-dependency-tracking --enable-asan --enable-debug --enable-debug-kmem

Include any warning/errors/backtraces from the system logs

...
  CC       asm-x86_64/aes/aeskey.lo
  CPPAS    asm-x86_64/aes/aes_amd64.lo
  CPPAS    asm-x86_64/aes/aes_aesni.lo
  CPPAS    asm-x86_64/modes/gcm_pclmulqdq.lo
  CPPAS    asm-x86_64/sha1/sha1-x86_64.lo
../../module/icp/core/kcf_mech_tabs.c: In function ‘kcf_create_mech_entry’:
../../module/icp/core/kcf_mech_tabs.c:324:11: error: ‘strncpy’ specified bound 32 equals destination size [-Werror=stringop-truncation]
    (void) strncpy(me_tab[i].me_name, mechname,
           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        CRYPTO_MAX_MECH_NAME);
        ~~~~~~~~~~~~~~~~~~~~~
  CPPAS    asm-x86_64/sha2/sha256_impl.lo
cc1: all warnings being treated as errors
make[3]: *** [Makefile:1006: core/kcf_mech_tabs.lo] Error 1
make[3]: *** Waiting for unfinished jobs....
make[3]: Leaving directory '/root/zfs/zfs/lib/libicp'
make[2]: *** [Makefile:610: all-recursive] Error 1
make[2]: Leaving directory '/root/zfs/zfs/lib'
make[1]: *** [Makefile:782: all-recursive] Error 1
make[1]: Leaving directory '/root/zfs/zfs'
make: *** [Makefile:651: all] Error 2

[dioni21]

BTW:

# gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-redhat-linux/8/lto-wrapper
OFFLOAD_TARGET_NAMES=nvptx-none
OFFLOAD_TARGET_DEFAULT=1
Target: x86_64-redhat-linux
Configured with: ../configure --enable-bootstrap --enable-languages=c,c++,fortran,objc,obj-c++,ada,go,lto --prefix=/usr --mandir=/usr/share/man --infodir=/usr/share/info --with-bugurl=http://bugzilla.redhat.com/bugzilla --enable-shared --enable-threads=posix --enable-checking=release --enable-multilib --with-system-zlib --enable-__cxa_atexit --disable-libunwind-exceptions --enable-gnu-unique-object --enable-linker-build-id --with-gcc-major-version-only --with-linker-hash-style=gnu --enable-plugin --enable-initfini-array --with-isl --enable-libmpx --enable-offload-targets=nvptx-none --without-cuda-driver --enable-gnu-indirect-function --enable-cet --with-tune=generic --with-arch_32=i686 --build=x86_64-redhat-linux
Thread model: posix
gcc version 8.1.1 20180712 (Red Hat 8.1.1-5) (GCC) 

[behlendorf]

@dioni21 thanks for filing this. When Fedora 28 was first released with gcc 8.1 we fixed a bunch of these kinds of warnings, see commit 21a4f5c. I thought we'd gotten all of them since our Fedora 28 builds have been cleanly passing since then. But clearly we missed at least one. Although I'm not sure why your additional build options would have caused it.

[dioni21]

Sent my first github PR. Hope it is ok.

[behlendorf]

@dioni21 thanks!