Odd warning from check_abi: Warning: Num of global symbols in libxdp.o xsk.o (68) does NOT match with num of versioned symbols in libxdp.so (71)

Question

Odd warning from check_abi: Warning: Num of global symbols in libxdp.o xsk.o (68) does NOT match with num of versioned symbols in libxdp.so (71)

hhoffstaette opened this issue a year ago · comments

After getting 1.3.1 to build properly (thanks!) the Gentoo CI promptly found .. "something", but we're not really sure what causes it.
The report is here (with log attached): https://bugs.gentoo.org/899742

As stated in the bug I cannot recreate this at all when building myself - I get no warnings from ar creating the libxdp archive, using the same toolchain options, binutils, elfutils etc.
Any idea what might be responsible for the ar warnings from the check_abi target?

Toke Høiland-Jørgensen · Answer 1 · Mon Mar 06 2023 19:41:37 GMT+0800 (China Standard Time)

Holger Hoffstätte ***@***.***> writes:

After getting 1.3.1 building properly (thanks!) our CI promptly found .. "something", but we're not really sure what it is. The report is here (with log attached): https://bugs.gentoo.org/899742 As stated in the bug I cannot recreate this at all when building myself - I get no warnings from ar creating the libxdp archive, using the same toolchain options, binutils, elfutils etc. Any idea what might be responsible for the ar warnings from the check_abi target?

The libxdp Makefile contains this check. My guess would be that maybe the CI system is missing one of the utilities used to compute those numbers, most likely 'readelf'? They're defined as: GLOBAL_SYM_COUNT = $(shell readelf -s --wide $(XDP_IN_SHARED) | \ cut -d "@" -f1 | sed 's/_v[0-9]_[0-9]_[0-9].*//' | \ sed 's/\[.*\]//' | \ awk '/GLOBAL/ && /DEFAULT/ && !/UND/ {print $$NF}' | \ sort -u | wc -l) VERSIONED_SYM_COUNT = $(shell readelf --dyn-syms --wide $(OBJDIR)/libxdp.so | \ grep -Eo '[^ ***@***.***_' | cut -d@ -f1 | sort -u | wc -l)

Holger Hoffstätte · Answer 2 · Mon Mar 06 2023 19:48:12 GMT+0800 (China Standard Time)

Thanks for the idea, but a missing readelf seems unlikely since it's part of binutils and the CI has the same version as I do (and I can build & use everything just fine). So it seems there's definitely something off in the CI - we'll keep looking.

Toke Høiland-Jørgensen · Answer 3 · Mon Mar 06 2023 20:06:11 GMT+0800 (China Standard Time)

Holger Hoffstätte ***@***.***> writes:

Thanks for the idea, but a missing readelf seems unlikely since it's part of binutils and the CI has the same version as I do (and I can build & use everything just fine). So it seems there's definitely something off in the CI - we'll keep looking.

Ah, yes, silly me, should have read the error message a bit closer: it does actually output numbers. There's also a diff of which lines are more in the VERSIONED_SYM_COUNTS in that build.log:

…

--- libxdp_global_syms.tmp 2023-03-05 15:41:12.831147643 +0100 +++ libxdp_versioned_syms.tmp 2023-03-05 15:41:12.841148037 +0100 @@ -1,3 +1,6 @@ +LIBXDP_1.0.0 +LIBXDP_1.2.0 +LIBXDP_1.3.0 libxdp_clean_references libxdp_get_error so it seems it's those three symbol version lines that make it into the output of the versioned syms? Not sure why that is, though; a different readelf version perhaps?

Holger Hoffstätte · Answer 4 · Tue Mar 28 2023 03:08:27 GMT+0800 (China Standard Time)

I'm closing this for now since it's likely caused by some Gentoo toolchain issues, since we support multiple installed gcc and llvm/clang versions and it looks likely someone somehow crossed their streams. If and when we figure out what exactly (if anything) is wrong in xdp-tools we can open a separate PR for the fix.