error during compilation

[antonellocaroli]

I get this error after the command:

make -C "$(mmaketool --toppath)/build/$(mmaketool --userbuild)"

nice cc -I. -I./../../include -I/build/onload/src/include -I/build/onload/src/lib/citools    -fPIC  -m64  -Werror -Wall -Wundef -Wpointer-arith -Wstrict-prototypes -Wnested-externs -Wno-stringop-truncation -Wno-format-truncation -Wimplicit-fallthrough=2 -Wno-array-bounds -Wno-stringop-overflow -Wno-deprecated-declarations -DTRANSPORT_CONFIG_OPT_HDR='<ci/internal/transport_config_opt_extra.h>' -mpclmul -msse4.1 -O2 -g $cflags $cppflags -c /build/onload/src/lib/citools/ippacket.c -o ci_tools_ippacket.o
nice cc -I. -I./../../include -I/build/onload/src/include -I/build/onload/src/lib/citools    -fPIC  -m64  -Werror -Wall -Wundef -Wpointer-arith -Wstrict-prototypes -Wnested-externs -Wno-stringop-truncation -Wno-format-truncation -Wimplicit-fallthrough=2 -Wno-array-bounds -Wno-stringop-overflow -Wno-deprecated-declarations -DTRANSPORT_CONFIG_OPT_HDR='<ci/internal/transport_config_opt_extra.h>' -mpclmul -msse4.1 -O2 -g $cflags $cppflags -c /build/onload/src/lib/citools/namespace.c -o ci_tools_namespace.o
nice cc -I. -I./../../include -I/build/onload/src/include -I/build/onload/src/lib/citools    -fPIC  -m64  -Werror -Wall -Wundef -Wpointer-arith -Wstrict-prototypes -Wnested-externs -Wno-stringop-truncation -Wno-format-truncation -Wimplicit-fallthrough=2 -Wno-array-bounds -Wno-stringop-overflow -Wno-deprecated-declarations -DTRANSPORT_CONFIG_OPT_HDR='<ci/internal/transport_config_opt_extra.h>' -mpclmul -msse4.1 -O2 -g $cflags $cppflags -c /build/onload/src/lib/citools/get_cpu_khz.c -o ci_tools_get_cpu_khz.o
nice cc -I. -I./../../include -I/build/onload/src/include -I/build/onload/src/lib/citools    -fPIC  -m64  -Werror -Wall -Wundef -Wpointer-arith -Wstrict-prototypes -Wnested-externs -Wno-stringop-truncation -Wno-format-truncation -Wimplicit-fallthrough=2 -Wno-array-bounds -Wno-stringop-overflow -Wno-deprecated-declarations -DTRANSPORT_CONFIG_OPT_HDR='<ci/internal/transport_config_opt_extra.h>' -mpclmul -msse4.1 -O2 -g $cflags $cppflags -c /build/onload/src/lib/citools/log_fn.c -o ci_tools_log_fn.o
/build/onload/src/lib/citools/log_fn.c: In function ‘ci_log_stderr’:
/build/onload/src/lib/citools/log_fn.c:30:3: error: ignoring return value of ‘writev’ declared with attribute ‘warn_unused_result’ [-Werror=unused-result]
   30 |   writev(STDERR_FILENO, v, 2);
      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~
/build/onload/src/lib/citools/log_fn.c: In function ‘ci_log_stdout’:
/build/onload/src/lib/citools/log_fn.c:43:3: error: ignoring return value of ‘writev’ declared with attribute ‘warn_unused_result’ [-Werror=unused-result]
   43 |   writev(STDOUT_FILENO, v, 2);
      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors
make[2]: *** [/build/onload/mk/after.mk:151: ci_tools_log_fn.o] Error 1
make[2]: Leaving directory '/build/onload/build/gnu_x86_64/lib/citools'
make[1]: *** [/build/onload/src/lib/mmake.mk:19: all] Error 2
make[1]: Leaving directory '/build/onload/build/gnu_x86_64/lib'
make: *** [/build/onload/src/mmake.mk:25: all] Error 2
make: Leaving directory '/build/onload/build/gnu_x86_64

[ol-alexandra]

We disable this warning for Ubuntu, see https://github.com/Xilinx-CNS/onload/blob/master/scripts/mmakebuildtree#L306 You can add a similar fix for your distro, or you can use make MMAKE_LIBERAL=1 to disable -Werror.

Probably we can add -Wno-unused-result in all the cases, because we don't support old gcc which does not understand such a parameter... I'll check.

[ol-alexandra]

No, we do not want to add -Wno-unused-result, because we really want such warnings. However some unreasonable distros require us to check write() result. We are trying to log an error. What can we do when logging fails?..

So this issue is not going to be fixed unless you provide a patch which sets W_NO_UNUSED_RESULT in your particular case, similar to Ubuntu.