kld

kld is the linker of the Kairo toolchain: LLD, run in-process, for ELF, Mach-O, PE/COFF (including MinGW) and WebAssembly. You rarely call it yourself. kairo and kcc link through it, and the toolchain ships no separate ld.lld.

kld -flavor gnu -o app main.o foo.o   # ELF
kld -flavor link /out:app.exe main.obj

-flavor takes the same values as lld: gnu (ELF), darwin (Mach-O), link (COFF), wasm and mingw. Everything else is lld's own command line.

When it runs

Normally the compiler links inside its own process and kld is not started. kld runs as a separate process when:

• the link needs lld options that change global state (-mllvm, --plugin-opt=-...);
• an earlier in-process link in the same run failed in a way that left lld unable to run again.

For these the compiler looks for kld in the same bin/ directory as itself, and a missing kld is a fatal error naming the path.

The C++ ABI check

Because kairo and kcc both use the same pinned compiler, the objects of one program agree on layout and mangling. At link time the linker driver also verifies the contract recorded in those objects, so an object built by a different compiler version is reported as a link error instead of misbehaving at run time. See kairo, kcc & Cross-compilation and ABI Compatibility.