### es0_contrast (guard-only f7 + guard+types f67 for n=0..8; verbatim n<=6 clean, n=7 hangs)
guarded f7 (es==0 guard only) es=0 n=0: returned, cmp_calls=0
guarded f7 (es==0 guard only) es=0 n=1: returned, cmp_calls=0
guarded f7 (es==0 guard only) es=0 n=2: returned, cmp_calls=0
guarded f7 (es==0 guard only) es=0 n=3: returned, cmp_calls=0
guarded f7 (es==0 guard only) es=0 n=4: returned, cmp_calls=0
guarded f7 (es==0 guard only) es=0 n=5: returned, cmp_calls=0
guarded f7 (es==0 guard only) es=0 n=6: returned, cmp_calls=0
guarded f7 (es==0 guard only) es=0 n=7: returned, cmp_calls=0
guarded f7 (es==0 guard only) es=0 n=8: returned, cmp_calls=0
guarded f67 es=0 n=0: returned, cmp_calls=0
guarded f67 es=0 n=1: returned, cmp_calls=0
guarded f67 es=0 n=2: returned, cmp_calls=0
guarded f67 es=0 n=3: returned, cmp_calls=0
guarded f67 es=0 n=4: returned, cmp_calls=0
guarded f67 es=0 n=5: returned, cmp_calls=0
guarded f67 es=0 n=6: returned, cmp_calls=0
guarded f67 es=0 n=7: returned, cmp_calls=0
guarded f67 es=0 n=8: returned, cmp_calls=0
verbatim  es=0 n=0: returned, cmp_calls=0
verbatim  es=0 n=1: returned, cmp_calls=0
verbatim  es=0 n=2: returned, cmp_calls=0
verbatim  es=0 n=3: returned, cmp_calls=0
verbatim  es=0 n=4: returned, cmp_calls=0
verbatim  es=0 n=5: returned, cmp_calls=0
verbatim  es=0 n=6: returned, cmp_calls=0
verbatim  es=0 n=7: expected to hang (see 'es0 hang' mode)
rc=0 (expect 0)
### es0_hang (verbatim es=0 n=64: partition loop never advances pb -> non-termination)
ES0 HANG CONFIRMED: comparator called 5,000,000 times with es=0 (pb frozen at +0; a correct 64-element sort needs <3000) (calls=5000000)
rc=7 (expect 7 = hang confirmed)
### es0_segv (verbatim es=0 n=7: swapcode do-while executes ONCE at n==0 -> 8-byte access at base)
ES0 ACCESS CONFIRMED (verbatim): SIGSEGV inside kqsort with es=0 n=7 (8-byte self-swap load at base of a zero-length array)
rc=0 (expect 0 = SIGSEGV confirmed)
### es0_segv_f7 (guard-only fix: returns cleanly, no access)
es0_segv(2): child exited st=0 (no fault)
rc=0 (expect 0, no fault)
OVERALL: ALL_EXPECTATIONS_MET