The C/C++ LSP's explicit-template-argument call path (template_function, e.g. Using<Fmt>(v)) filled a stack array const CBMType *targs[16] without NULL-terminating it before cbm_type_substitute. With more declared type params than explicit args (bitcoin src/serialize.h: Using's Wrapper<Formatter, T&> with 2 params, 1 arg), the bounded args walk read uninitialized stack; any non-NULL garbage got bound to the type param and woven into the REGISTERED return-type graph, then dereferenced at a later call site - SIGSEGV (crash shape: string bytes misread as a CBMType*). All c_lsp targs arrays are now zero-filled, and cbm_type_substitute's args walk treats implausible values (misaligned / below the first page) as the terminator so contract violations can never leak garbage into a type graph. Reproduce-first: deterministic poison-args unit test (typerep_substitute_rejects_garbage_args_entries) + real-repo verification (bitcoin indexes clean under ASan; was a deterministic SIGSEGV).
Martin Vogel
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