__res_search@GLIBC_2.2.5 issues on glibc < 2.34

[malt3]

Hey, I'm just creating this issue to document the current state and maybe keep everyone updated.

The definition of __res_search and other symbols has changed between glibc versions, leading to linking issues when using zig cc on glibc < 2.34 (amd64).

Known functions that need special handling:

• fcnt64
• dn_expad
• res_search
• res_query
• res_nquery

The issue is this one:

I still see this issue with Go 1.20 and zig 0.11.0-dev.811+8ff9284c4.

(20:10:30) ERROR: /private/var/tmp/_bazel_thomas/d95eb470615df18f91feffc144a9a015/external/com_github_sourcegraph_sourcegraph/cmd/migrator/BUILD.bazel:16:10: GoLink external/com_github_sourcegraph_sourcegraph/cmd/migrator/migrator_/migrator failed: (Exit 1): sandbox-exec failed: error executing command 
  (cd /private/var/tmp/_bazel_thomas/d95eb470615df18f91feffc144a9a015/sandbox/darwin-sandbox/21777/execroot/sourcegraph_oss && \
  exec env - \
    CGO_ENABLED=1 \
    GOARCH=amd64 \
    GOOS=linux \
    GOPATH='' \
    GOROOT=bazel-out/darwin_arm64-fastbuild-ST-0b20c6396c42/bin/external/io_bazel_rules_go/stdlib_ \
    GOROOT_FINAL=GOROOT \
    PATH=external/zig_sdk/tools/x86_64-linux-gnu.2.28:/bin:/usr/bin \
    TMPDIR=/var/folders/ws/lyfqx2sn72v223fhz5kb77m40000gp/T/ \
  /usr/bin/sandbox-exec -f /private/var/tmp/_bazel_thomas/d95eb470615df18f91feffc144a9a015/sandbox/darwin-sandbox/21777/sandbox.sb /var/tmp/_bazel_thomas/install/730b09b9d9f2bfd30b4c0a074ba23835/process-wrapper '--timeout=0' '--kill_delay=15' '--stats=/private/var/tmp/_bazel_thomas/d95eb470615df18f91feffc144a9a015/sandbox/darwin-sandbox/21777/stats.out' bazel-out/darwin_arm64-opt-exec-2B5CBBC6-ST-625e526ca8a8/bin/external/go_sdk/builder_reset/builder '-param=bazel-out/darwin_arm64-fastbuild-ST-4a519fd6d3e4/bin/external/com_github_sourcegraph_sourcegraph/cmd/migrator/migrator_/migrator-0.params' -- -extld external/zig_sdk/tools/x86_64-linux-gnu.2.28/c++ '-buildid=redacted' -extldflags '-fno-lto -Wl,-S')
net(.text): relocation target __res_search@GLIBC_2.2.5 not defined
os/user(.text): relocation target memset not defined
os/user(.text): relocation target memcpy not defined
runtime/cgo(.text): relocation target memset not defined
link: error running subcommand external/go_sdk/pkg/tool/darwin_arm64/link: exit status 2

There are two attempted workarounds in bazel-zig-cc (7b0de33 and 8d1e1c9) that do not fully resolve this issue.

@motiejus also stated

We agreed with @andrewrk that we will change the offending headers in upsteam zig (add ifdefs on glibc version). To my latest knowledge, @sywhang is working on that.

My goal here is to document that the issue still exists and have a place to share updates.

Edit: Fix PR was opened 🎉

[motiejus]

Thanks for the update, we are aware of this, and aware that the workaround in bazel-zig-cc does not fully resolve the issue.

The fix is known but not yet implemented; @sywhang just didn't get to that yet (the Go 1.20 upgrade has been tough). If you are inclined to do some #ifdefs for a couple of functions in Zig upstream, you are welcome.

Here are the list of functions that need special handling that Uber currently works around internally:

• fcnt64
• dn_expad
• res_search
• res_query
• res_nquery

The list is exhaustive of the functions that we do have workarounds for, but it is likely there are more offenders.

Related: ziglang/zig#9485

I will leave this issue open until this is solved upstream by either/or:

• short-term: a header patch with an #ifdef(__GLIBC__, <...>) to Zig upstream.
• long-term: universal-headers

[motiejus]

Fixed with #30 (or at least we will know it's fixed after I bring all the unit tests and infrastructure to order).