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Avoid (most) uses of XCAR/XCDR as lvalues, for flexibility in experimenting

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with lisp system changes.
This commit is contained in:
Ken Raeburn 2001-10-16 09:09:51 +00:00
parent 018ba359ab
commit f3fbd15535
29 changed files with 350 additions and 193 deletions
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64
src/lisp.h
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@ -248,6 +248,16 @@ Lisp_Object;
#endif /* WORDS_BIG_ENDIAN */
#ifdef __GNUC__
static __inline__ Lisp_Object
LISP_MAKE_RVALUE (Lisp_Object o)
{
return o;
}
#else
#define LISP_MAKE_RVALUE(o) (o) /* XXX - keeps arg as rvalue. */
#endif
#endif /* NO_UNION_TYPE */
@ -255,6 +265,7 @@ Lisp_Object;
#ifdef NO_UNION_TYPE
#define Lisp_Object EMACS_INT
#define LISP_MAKE_RVALUE(o) (0+(o))
#endif /* NO_UNION_TYPE */
#ifndef VALMASK
@ -616,14 +627,43 @@ struct Lisp_Cons
};
/* Take the car or cdr of something known to be a cons cell. */
/* The _AS_LVALUE macros shouldn't be used outside of the minimal set
of code that has to know what a cons cell looks like. Other code not
part of the basic lisp implementation should assume that the car and cdr
fields are not accessible as lvalues. (What if we want to switch to
a copying collector someday? Cached cons cell field addresses may be
invalidated at arbitrary points.) */
#ifdef HIDE_LISP_IMPLEMENTATION
#define XCAR(c) (XCONS ((c))->car_)
#define XCDR(c) (XCONS ((c))->cdr_)
#define XCAR_AS_LVALUE(c) (XCONS ((c))->car_)
#define XCDR_AS_LVALUE(c) (XCONS ((c))->cdr_)
#else
#define XCAR(c) (XCONS ((c))->car)
#define XCDR(c) (XCONS ((c))->cdr)
#define XCAR_AS_LVALUE(c) (XCONS ((c))->car)
#define XCDR_AS_LVALUE(c) (XCONS ((c))->cdr)
#endif
/* Okay, we're not quite ready to turn this on yet. A few files still
need to be updated and tested. */
#undef LISP_MAKE_RVALUE
#define LISP_MAKE_RVALUE(x) (x)
/* Use these from normal code. */
#define XCAR(c) LISP_MAKE_RVALUE(XCAR_AS_LVALUE(c))
#define XCDR(c) LISP_MAKE_RVALUE(XCDR_AS_LVALUE(c))
/* Use these to set the fields of a cons cell.
Note that both arguments may refer to the same object, so 'n'
should not be read after 'c' is first modified. Also, neither
argument should be evaluated more than once; side effects are
especially common in the second argument. */
#define XSETCAR(c,n) (XCAR_AS_LVALUE(c) = (n))
#define XSETCDR(c,n) (XCDR_AS_LVALUE(c) = (n))
/* For performance: Fast storage of positive integers into the
fields of a cons cell. See above caveats. */
#define XSETCARFASTINT(c,n) XSETFASTINT(XCAR_AS_LVALUE(c),(n))
#define XSETCDRFASTINT(c,n) XSETFASTINT(XCDR_AS_LVALUE(c),(n))
/* Take the car or cdr of something whose type is not known. */
#define CAR(c) \
(CONSP ((c)) ? XCAR ((c)) \
@ -1474,6 +1514,22 @@ typedef unsigned char UCHAR;
#define CHECK_OVERLAY(x, i) \
do { if (!OVERLAYP ((x))) x = wrong_type_argument (Qoverlayp, (x));} while (0)
/* Since we can't assign directly to the CAR or CDR fields of a cons
cell, use these when checking that those fields contain numbers. */
#define CHECK_NUMBER_CAR(x, i) \
do { \
Lisp_Object tmp = XCAR (x); \
CHECK_NUMBER (tmp, (i)); \
XSETCAR ((x), tmp); \
} while (0)
#define CHECK_NUMBER_CDR(x, i) \
do { \
Lisp_Object tmp = XCDR (x); \
CHECK_NUMBER (tmp, (i)); \
XSETCDR ((x), tmp); \
} while (0)
/* Cast pointers to this type to compare them. Some machines want int. */
#ifndef PNTR_COMPARISON_TYPE
#define PNTR_COMPARISON_TYPE EMACS_UINT