The !defined(NoDbgRegParms) phrase allows someone to define an alternative on the command line via a -D argument, so it allows the

    # define NoDbgRegParms __attribute__ ((regparm (0)))

def to be a default, rather thna the only way.

PRODUCTION is defined in platforms/Cross/vm/sqAssert.h

#undef assert
# define __stringify(foo) #foo
# define __stringifyNum(n) __stringify(n)
#ifdef NDEBUG /* compatible with Mac OS X (FreeBSD) /usr/include/assert.h */
# define assert(expr) 0 /* hack disabling of asserts. Better in makefile? */
# define asserta(expr) (expr)
# define assertf(msg) 0
# define assertl(expr,line) 0
# define assertal(expr,line) (expr)
# define assertfl(msg,line) 0
# define PRODUCTION 1
#elif 1
# define assert(expr) ((expr)||(warning(#expr " " __stringifyNum(__LINE__)),0))
# define asserta(expr) ((expr)||(warning(#expr " " __stringifyNum(__LINE__)),0))
# define assertf(msg) (warning(#msg " " __stringifyNum(__LINE__)),0)
# define assertl(expr,line) ((expr)||(warningat(#expr,line),0))
# define assertal(expr,line) ((expr)||(warningat(#expr,line),0))
# define assertfl(msg,line) (warningat(#msg,line),0)
# define PRODUCTION 0
#endif