tryConnect built the xce_client_config_t with C.CString(host/from/key), then a
defer freed all three. But xcecli_ctx_init stores the config POINTER
(ctx->conf = config), not a copy — client_failover.c dereferences
config->masters/from/key for the client's ENTIRE lifetime (e.g.
xce_failover_next_target strncpy's a master host on every write-fail/redirect).
Freeing the strings left config->masters[0] dangling → ASAN heap-use-after-free
(strncpy in the background C thread) after a few submits.
Fix: keep the three C strings for the process lifetime (tryConnect runs once at
startup, gCtx is a process-global); free them only on the init-failure path.
Verified: 6 consecutive job submits, apiserver stays up, 0 ASAN errors
(previously crashed after ~2-3 submits).
Co-Authored-By: Claude <noreply@anthropic.com>
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