feat: variadic function support + go vet clean (v0.5.2)#49
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Zero-value (0) means non-variadic, preserving full backward compatibility. Values >0 indicate the number of fixed parameters before '...' in the C prototype. On Apple ARM64, this boundary triggers register exhaustion.
Wraps PrepareCallInterface and sets FixedArgCount on the resulting CIF. Validates nfixedargs is non-negative and does not exceed total arg count. On Apple ARM64, the Execute() method reads FixedArgCount to exhaust register allocators at the fixed/variadic boundary per Apple AAPCS64.
…Darwin Apple's AAPCS64 extension requires that all variadic arguments go on the stack regardless of register availability. When FixedArgCount > 0 and GOOS == darwin, the Execute() method sets gprIdx=8 and fprIdx=8 before processing the first variadic argument, forcing subsequent arguments into stack slots. This matches Apple clang and libffi ffi_prep_cif_var() on Darwin ARM64. Non-variadic CIFs (FixedArgCount == 0) and non-Darwin ARM64 targets are completely unaffected — the branch is never entered.
Add sum_variadic and variadic_two_fixed to testdata/structtest.c. Add ffi/variadic_e2e_test.go with three test functions: - TestVariadic_SumIntegers (nfixedargs=1, result=60) - TestVariadic_TwoFixed (nfixedargs=2, result=600) - TestVariadic_ErrorValidation (validation edge cases) Extend struct_e2e_test.go build tag from amd64-only to (amd64 || arm64) so that requireStructLib/structTestLib are available to variadic tests on arm64 hosts. Move the four AMD64-specific XMM struct return tests to a new ffi/struct_return_e2e_amd64_test.go with amd64-only build tag.
Compiles testdata/structtest.c via gcc and exercises both sum_variadic and variadic_two_fixed through PrepareVariadicCallInterface. Exits 0 on PASS, 1 on FAIL, 0 with SKIP message if gcc is unavailable. Runs on linux/darwin/freebsd (amd64 and arm64). Primary use: Apple Silicon verification — confirms variadic args land on the stack on darwin/arm64 as required by Apple AAPCS64 extension.
…ECTURE, ROADMAP CHANGELOG: add Unreleased section with PrepareVariadicCallInterface, Apple ARM64 stack-force, cmd/variadic-test, and variadic e2e tests. README: replace 'Variadic not supported' limitation with Apple ARM64 note; add variadic feature row to table; add variadic example; update roadmap table. ARCHITECTURE: add Variadic Function Support section explaining platform differences, FixedArgCount field semantics, and Darwin ARM64 register flush. ROADMAP: mark variadic as in-progress in v0.6.0 milestone.
- dl_unix.go: use double-indirection for dlopen/dlsym uintptr→Pointer (go.dev/issue/58625) - syscall_linux_stub.s: remove unused uint64 return from syscallStub signature (returns via struct field)
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Summary
PrepareVariadicCallInterface(cif, convention, nfixedargs, returnType, argTypes)for C variadic functions (printf, XCreateIC, etc.). Apple ARM64: variadic args forced to stack per Apple ABI. Closes Support for variadic functions on darwin/arm64 (Apple Silicon) #47dl_unix.gounsafe.Pointer warnings (double-indirection per Go #58625),syscall_linux_stub.sreturn signature mismatchdocs/dev/references from CHANGELOGcmd/variadic-test— standalone binary for Apple Silicon verificationTest plan
go build ./...— all 6 platformsgo vet ./...— 0 warnings (WSL Linux)go fmt ./...— cleango test ./ffi ./types ./internal/...— all passCGO_ENABLED=1 go test -race— all pass (WSL Linux)[0.5.2] - 2026-05-25header included