test/bounce — format-bounce stress corpus

Stresses kit's object read/write/reloc, archive, and partial-link machinery by taking one compiled program and bouncing its relocatable object through chains of format conversions and toolchain transforms, relinking, and checking the result still computes the right answer. Cross-arch run coverage lives elsewhere (test/link, test/smoke); this corpus exercises the format paths, not the arches.

Run with make test-bounce (opt-in; needs podman/qemu + a host cc).

Cases

cases/NN_name.c each define int bounce_main(void) returning a value in [0,127]. They are portable LP64 integer C, so the host-cc result is the oracle every target and every bounce chain must reproduce. crt/crt.c is the freestanding _start: it calls bounce_main with a normal C call (so the compiler emits a real cross-TU relocation — the edge under test) and exits via exit_group with the return value.

Chains

For each (arch, case, -O level) the program is compiled to one .o, then each chain rebuilds an executable from it and runs it:

Chain	Transform	Stresses
direct	link straight through	baseline
macho_rt	ELF → Mach-O → ELF (objcopy)	macho_emit/macho_read + reloc xlate
coff_rt	ELF → COFF → ELF (objcopy)	coff_emit/coff_read + reloc xlate
tri_rt	ELF → Mach-O → COFF → ELF	chained round-trip
ldr	ld -r partial-link merge → link	relocatable output
strip_dbg	objcopy --strip-debug → link	strip + reduced symtab
ar	ar rcs → on-demand link	GNU archive index r/w + symbol resolution

A chain only runs where every format it routes through is a real kit target for that arch:

Format	Arches
ELF	all (Linux / freestanding)
COFF	x64, aarch64 (Windows)
Mach-O	aarch64 only (Apple Silicon; kit does not target x64 Mach-O)

So macho_rt/tri_rt run on aarch64 only, coff_rt on aarch64+x64, and the ELF-only chains everywhere.

Arches

Defaults to the host-native Linux arch (no emulation). Sweep others with KIT_BOUNCE_ARCHES="aarch64 x64 rv64". Optimization levels default to 0 1 (override with KIT_BOUNCE_OPTS).

Conventions

Skip-vs-fail mirrors the smoke harness: a skip counts as failure unless KIT_TEST_ALLOW_SKIP=1. Add a case by dropping a cases/NN_name.c that defines bounce_main; no other wiring is needed.