Hello @klayoutmatthias,

First of all, thank you for your efforts in preparing the 0.30.3 release.

Description of the issue
Building the current master branch on macOS Sequoia (Intel) fails with an undefined symbol error related to db::Net when linking libklayout_db.

Environment:

• macOS Sequoia 15.6 (Intel)
• Apple clang version 17.0.0 (clang-1700.0.13.5)
• Target: x86_64-apple-darwin24.6.0
• KLayout commit: 10a34cc (master branch, 0.30.3-to-be)
  (built locally with a slight modification: ef365b55 to bypass the link error)
• Build system: build4mac.py with the default options.

Error log:

Undefined symbols for architecture x86_64:
"gsi::ClassBase const* gsi::cls_decldb::Net()", referenced from:
db::MeasureNetEval::net_func() const in dbMeasureEval.o
ld: symbol(s) not found for architecture x86_64
clang++: error: linker command failed with exit code 1 (use -v to see invocation)

Analysis (by ChatGPT):
The function MeasureNetEval::net_func() (in src/db/dbMeasureEval.cc) calls:

return tl::Variant::make_variant_ref(n->second);

where n->second is a const db::Net*.
This requires a GSI binding for db::Net (gsi::cls_decldb::Net()).
I confirmed that such a binding does not exist in the current source tree by searching (grep -R "cls_decl<db::Net>" src/), which returned no results.

This causes a link error on macOS (and possibly other platforms with stricter linking).
It may have been macOS’s stricter linker that surfaced this issue.

Workaround (by ChatGPT):
As a temporary fix, replacing the line (Left) with a dummy return tl::Variant(); (Right) allows the build to complete.

Rebuild:
Succeeded 😄

Best regards,
Kazzz-S