[0xbadcafebee]

  memmove(args->begin_argv + extend, args->begin_argv + consume,
      args->endp - args->begin_argv + consume);   // ← bug

C code like this is why we can't have nice things. Arithmetic operation in the arguments of a dangerous function call with no explicit bounds check.

[sethops1]

"I just don't write bugs"

Yeah.