RE_CONTEXT_INVALID_DUP
# define RE_NO_SUB (RE_CONTEXT_INVALID_DUP << 1)
(_RE_SYNTAX_POSIX_COMMON | RE_BK_PLUS_QM | RE_CONTEXT_INVALID_DUP)
if (syntax & RE_CONTEXT_INVALID_DUP)
if ((syntax & RE_CONTEXT_INVALID_DUP)