#if	!defined(__safe_alloca__)
#define	__safe_alloca__

#include <assert.h>

#if	!defined(NDEBUG)

#define	FIREWALL_START	0x940504FE
#define	FIREWALL_STOP_0	0xEE
#define	FIREWALL_STOP_1	0x41
#define	FIREWALL_STOP_2	0x51
#define	FIREWALL_STOP_3	0x59

/*
 * I don't like this implementation, but it works.
 */

#define	SAFE_DECL()		\
    unsigned long ___newsize;	\
    unsigned char *___tempptr

#define	SAFE_alloca(size)				\
    (							\
 	___newsize  = (size) + 3 * sizeof(long),	\
	___tempptr = alloca(___newsize),		\
	((long *)___tempptr)[0] = ___newsize,		\
	((long *)___tempptr)[1] = FIREWALL_START,	\
	___tempptr[___newsize-4]   = FIREWALL_STOP_0,	\
	___tempptr[___newsize-3]   = FIREWALL_STOP_1,	\
	___tempptr[___newsize-2]   = FIREWALL_STOP_2,	\
	___tempptr[___newsize-1]   = FIREWALL_STOP_3,	\
	(void *) (___tempptr + 2 * sizeof(long))	\
    )

#define	ASSERT_SAFE(var)					\
    do {							\
	___tempptr = (unsigned char *) (var);			\
	___tempptr -= 2 * sizeof(long);				\
	assert(((long *)___tempptr)[1] == FIREWALL_START);	\
	___newsize = ((long *)___tempptr)[0];			\
	assert(___tempptr[___newsize-4] == FIREWALL_STOP_0);	\
	assert(___tempptr[___newsize-3] == FIREWALL_STOP_1);	\
	assert(___tempptr[___newsize-2] == FIREWALL_STOP_2);	\
	assert(___tempptr[___newsize-1] == FIREWALL_STOP_3);	\
    } while (0)

#else	/* defined(NDEBUG) */

#define	SAFE_DECL()		unsigned long ___newsize
#define	SAFE_alloca(size)	alloca(size)
#define	ASSERT_SAFE(var)	do {} while (0)

#endif	/* defined(NDEBUG) */

#endif	/* !defined(__safe_alloca__) */