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Fix union Lisp_Fwd * alignment bug

Browse source 
It's not portable to cast (e.g.) struct Lisp_Objfwd * to union
Lisp_Fwd * and then back again, because the compiler can then assume
that the pointer is aligned for union Lisp_Fwd * when accessing
the struct Lisp_Objfwd * components, and this assumption might
be incorrect becase we don't force that alignment.
* src/lisp.h (lispfwd): New type, replacing ...
(union Lisp_Fwd): ... this type, which was removed.
All uses changed.
(SET_SYMBOL_FWD): 2nd arg is now void *, not lispfwd.
All uses changed (casts no longer needed; they were
not portable anyway).
This commit is contained in:
Paul Eggert 2019-04-01 11:54:23 -07:00
parent 197fbfc71f
commit 9287813da1
5 changed files with 80 additions and 77 deletions
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8
src/buffer.c
View file

@ -1207,7 +1207,7 @@ buffer_local_value (Lisp_Object variable, Lisp_Object buffer)
result = Fassoc (variable, BVAR (buf, local_var_alist), Qnil);
if (!NILP (result))
{
if (blv->fwd)
if (blv->fwd.fwdptr)
{ /* What binding is loaded right now? */
Lisp_Object current_alist_element = blv->valcell;
@ -1228,7 +1228,7 @@ buffer_local_value (Lisp_Object variable, Lisp_Object buffer)
}
case SYMBOL_FORWARDED:
{
union Lisp_Fwd *fwd = SYMBOL_FWD (sym);
lispfwd fwd = SYMBOL_FWD (sym);
if (BUFFER_OBJFWDP (fwd))
result = per_buffer_value (buf, XBUFFER_OBJFWD (fwd)->offset);
else
@ -2140,7 +2140,7 @@ void set_buffer_internal_2 (register struct buffer *b)
Lisp_Object var = XCAR (XCAR (tail));
struct Lisp_Symbol *sym = XSYMBOL (var);
if (sym->u.s.redirect == SYMBOL_LOCALIZED /* Just to be sure. */
&& SYMBOL_BLV (sym)->fwd)
&& SYMBOL_BLV (sym)->fwd.fwdptr)
/* Just reference the variable
to cause it to become set for this buffer. */
Fsymbol_value (var);
@ -5444,7 +5444,7 @@ defvar_per_buffer (struct Lisp_Buffer_Objfwd *bo_fwd, const char *namestring,
bo_fwd->predicate = predicate;
sym->u.s.declared_special = true;
sym->u.s.redirect = SYMBOL_FORWARDED;
SET_SYMBOL_FWD (sym, (union Lisp_Fwd *) bo_fwd);
SET_SYMBOL_FWD (sym, bo_fwd);
XSETSYMBOL (PER_BUFFER_SYMBOL (offset), sym);
if (PER_BUFFER_IDX (offset) == 0)

74
src/data.c
View file

@ -42,49 +42,49 @@ static void swap_in_symval_forwarding (struct Lisp_Symbol *,
struct Lisp_Buffer_Local_Value *);
static bool
BOOLFWDP (union Lisp_Fwd *a)
BOOLFWDP (lispfwd a)
{
return XFWDTYPE (a) == Lisp_Fwd_Bool;
}
static bool
INTFWDP (union Lisp_Fwd *a)
INTFWDP (lispfwd a)
{
return XFWDTYPE (a) == Lisp_Fwd_Int;
}
static bool
KBOARD_OBJFWDP (union Lisp_Fwd *a)
KBOARD_OBJFWDP (lispfwd a)
{
return XFWDTYPE (a) == Lisp_Fwd_Kboard_Obj;
}
static bool
OBJFWDP (union Lisp_Fwd *a)
OBJFWDP (lispfwd a)
{
return XFWDTYPE (a) == Lisp_Fwd_Obj;
}
static struct Lisp_Boolfwd *
XBOOLFWD (union Lisp_Fwd *a)
XBOOLFWD (lispfwd a)
{
eassert (BOOLFWDP (a));
return &a->u_boolfwd;
return a.fwdptr;
}
static struct Lisp_Kboard_Objfwd *
XKBOARD_OBJFWD (union Lisp_Fwd *a)
XKBOARD_OBJFWD (lispfwd a)
{
eassert (KBOARD_OBJFWDP (a));
return &a->u_kboard_objfwd;
return a.fwdptr;
}
static struct Lisp_Intfwd *
XFIXNUMFWD (union Lisp_Fwd *a)
XFIXNUMFWD (lispfwd a)
{
eassert (INTFWDP (a));
return &a->u_intfwd;
return a.fwdptr;
}
static struct Lisp_Objfwd *
XOBJFWD (union Lisp_Fwd *a)
XOBJFWD (lispfwd a)
{
eassert (OBJFWDP (a));
return &a->u_objfwd;
return a.fwdptr;
}
static void
@ -669,7 +669,7 @@ global value outside of any lexical scope. */)
case SYMBOL_LOCALIZED:
{
struct Lisp_Buffer_Local_Value *blv = SYMBOL_BLV (sym);
if (blv->fwd)
if (blv->fwd.fwdptr)
/* In set_internal, we un-forward vars when their value is
set to Qunbound. */
return Qt;
@ -980,7 +980,7 @@ chain of aliases, signal a `cyclic-variable-indirection' error. */)
swap_in_symval_forwarding for that. */
Lisp_Object
do_symval_forwarding (union Lisp_Fwd *valcontents)
do_symval_forwarding (lispfwd valcontents)
{
switch (XFWDTYPE (valcontents))
{
@ -1071,7 +1071,8 @@ wrong_range (Lisp_Object min, Lisp_Object max, Lisp_Object wrong)
current buffer. This only plays a role for per-buffer variables. */
static void
store_symval_forwarding (union Lisp_Fwd *valcontents, register Lisp_Object newval, struct buffer *buf)
store_symval_forwarding (lispfwd valcontents, Lisp_Object newval,
struct buffer *buf)
{
switch (XFWDTYPE (valcontents))
{
@ -1178,12 +1179,12 @@ swap_in_global_binding (struct Lisp_Symbol *symbol)
struct Lisp_Buffer_Local_Value *blv = SYMBOL_BLV (symbol);
/* Unload the previously loaded binding. */
if (blv->fwd)
if (blv->fwd.fwdptr)
set_blv_value (blv, do_symval_forwarding (blv->fwd));
/* Select the global binding in the symbol. */
set_blv_valcell (blv, blv->defcell);
if (blv->fwd)
if (blv->fwd.fwdptr)
store_symval_forwarding (blv->fwd, XCDR (blv->defcell), NULL);
/* Indicate that the global binding is set up now. */
@ -1213,7 +1214,7 @@ swap_in_symval_forwarding (struct Lisp_Symbol *symbol, struct Lisp_Buffer_Local_
/* Unload the previously loaded binding. */
tem1 = blv->valcell;
if (blv->fwd)
if (blv->fwd.fwdptr)
set_blv_value (blv, do_symval_forwarding (blv->fwd));
/* Choose the new binding. */
{
@ -1227,7 +1228,7 @@ swap_in_symval_forwarding (struct Lisp_Symbol *symbol, struct Lisp_Buffer_Local_
/* Load the new binding. */
set_blv_valcell (blv, tem1);
if (blv->fwd)
if (blv->fwd.fwdptr)
store_symval_forwarding (blv->fwd, blv_value (blv), NULL);
}
}
@ -1255,7 +1256,9 @@ find_symbol_value (Lisp_Object symbol)
{
struct Lisp_Buffer_Local_Value *blv = SYMBOL_BLV (sym);
swap_in_symval_forwarding (sym, blv);
return blv->fwd ? do_symval_forwarding (blv->fwd) : blv_value (blv);
return (blv->fwd.fwdptr
? do_symval_forwarding (blv->fwd)
: blv_value (blv));
}
case SYMBOL_FORWARDED:
return do_symval_forwarding (SYMBOL_FWD (sym));
@ -1357,7 +1360,7 @@ set_internal (Lisp_Object symbol, Lisp_Object newval, Lisp_Object where,
We need to unload it, and choose a new binding. */
/* Write out `realvalue' to the old loaded binding. */
if (blv->fwd)
if (blv->fwd.fwdptr)
set_blv_value (blv, do_symval_forwarding (blv->fwd));
/* Find the new binding. */
@ -1404,12 +1407,12 @@ set_internal (Lisp_Object symbol, Lisp_Object newval, Lisp_Object where,
/* Store the new value in the cons cell. */
set_blv_value (blv, newval);
if (blv->fwd)
if (blv->fwd.fwdptr)
{
if (voide)
/* If storing void (making the symbol void), forward only through
buffer-local indicator, not through Lisp_Objfwd, etc. */
blv->fwd = NULL;
blv->fwd.fwdptr = NULL;
else
store_symval_forwarding (blv->fwd, newval,
BUFFERP (where)
@ -1421,7 +1424,7 @@ set_internal (Lisp_Object symbol, Lisp_Object newval, Lisp_Object where,
{
struct buffer *buf
= BUFFERP (where) ? XBUFFER (where) : current_buffer;
union Lisp_Fwd *innercontents = SYMBOL_FWD (sym);
lispfwd innercontents = SYMBOL_FWD (sym);
if (BUFFER_OBJFWDP (innercontents))
{
int offset = XBUFFER_OBJFWD (innercontents)->offset;
@ -1593,14 +1596,14 @@ default_value (Lisp_Object symbol)
But the `realvalue' slot may be more up to date, since
ordinary setq stores just that slot. So use that. */
struct Lisp_Buffer_Local_Value *blv = SYMBOL_BLV (sym);
if (blv->fwd && EQ (blv->valcell, blv->defcell))
if (blv->fwd.fwdptr && EQ (blv->valcell, blv->defcell))
return do_symval_forwarding (blv->fwd);
else
return XCDR (blv->defcell);
}
case SYMBOL_FORWARDED:
{
union Lisp_Fwd *valcontents = SYMBOL_FWD (sym);
lispfwd valcontents = SYMBOL_FWD (sym);
/* For a built-in buffer-local variable, get the default value
rather than letting do_symval_forwarding get the current value. */
@ -1688,13 +1691,13 @@ set_default_internal (Lisp_Object symbol, Lisp_Object value,
XSETCDR (blv->defcell, value);
/* If the default binding is now loaded, set the REALVALUE slot too. */
if (blv->fwd && EQ (blv->defcell, blv->valcell))
if (blv->fwd.fwdptr && EQ (blv->defcell, blv->valcell))
store_symval_forwarding (blv->fwd, value, NULL);
return;
}
case SYMBOL_FORWARDED:
{
union Lisp_Fwd *valcontents = SYMBOL_FWD (sym);
lispfwd valcontents = SYMBOL_FWD (sym);
/* Handle variables like case-fold-search that have special slots
in the buffer.
@ -1750,7 +1753,7 @@ for this variable. */)
union Lisp_Val_Fwd
{
Lisp_Object value;
union Lisp_Fwd *fwd;
lispfwd fwd;
};
static struct Lisp_Buffer_Local_Value *
@ -1770,7 +1773,10 @@ make_blv (struct Lisp_Symbol *sym, bool forwarded,
or keyboard-local forwarding. */
eassert (!(forwarded && BUFFER_OBJFWDP (valcontents.fwd)));
eassert (!(forwarded && KBOARD_OBJFWDP (valcontents.fwd)));
blv->fwd = forwarded ? valcontents.fwd : NULL;
if (forwarded)
blv->fwd = valcontents.fwd;
else
blv->fwd.fwdptr = NULL;
set_blv_where (blv, Qnil);
blv->local_if_set = 0;
set_blv_defcell (blv, tem);
@ -1941,7 +1947,7 @@ Instead, use `add-hook' and specify t for the LOCAL argument. */)
Otherwise, if C code modifies the variable before we load the
binding in, then that new value would clobber the default binding
the next time we unload it. See bug#34318. */
if (blv->fwd)
if (blv->fwd.fwdptr)
swap_in_symval_forwarding (sym, blv);
}
@ -1968,7 +1974,7 @@ From now on the default value will apply in this buffer. Return VARIABLE. */)
case SYMBOL_PLAINVAL: return variable;
case SYMBOL_FORWARDED:
{
union Lisp_Fwd *valcontents = SYMBOL_FWD (sym);
lispfwd valcontents = SYMBOL_FWD (sym);
if (BUFFER_OBJFWDP (valcontents))
{
int offset = XBUFFER_OBJFWD (valcontents)->offset;
@ -2051,7 +2057,7 @@ BUFFER defaults to the current buffer. */)
}
case SYMBOL_FORWARDED:
{
union Lisp_Fwd *valcontents = SYMBOL_FWD (sym);
lispfwd valcontents = SYMBOL_FWD (sym);
if (BUFFER_OBJFWDP (valcontents))
{
int offset = XBUFFER_OBJFWD (valcontents)->offset;
@ -2122,7 +2128,7 @@ If the current binding is global (the default), the value is nil. */)
case SYMBOL_PLAINVAL: return Qnil;
case SYMBOL_FORWARDED:
{
union Lisp_Fwd *valcontents = SYMBOL_FWD (sym);
lispfwd valcontents = SYMBOL_FWD (sym);
if (KBOARD_OBJFWDP (valcontents))
return Fframe_terminal (selected_frame);
else if (!BUFFER_OBJFWDP (valcontents))

41
src/lisp.h
View file

@ -797,6 +797,13 @@ INLINE void
#define XUNTAG(a, type, ctype) ((ctype *) \
((char *) XLP (a) - LISP_WORD_TAG (type)))
/* A forwarding pointer to a value. It uses a generic pointer to
avoid alignment bugs that could occur if it used a pointer to a
union of the possible values (struct Lisp_Objfwd, struct
Lisp_Intfwd, etc.). The pointer is packaged inside a struct to
help static checking. */
typedef struct { void *fwdptr; } lispfwd;
/* Interned state of a symbol. */
@ -862,7 +869,7 @@ struct Lisp_Symbol
Lisp_Object value;
struct Lisp_Symbol *alias;
struct Lisp_Buffer_Local_Value *blv;
union Lisp_Fwd *fwd;
lispfwd fwd;
} val;
/* Function value of the symbol or Qnil if not fboundp. */
@ -2171,10 +2178,10 @@ SYMBOL_BLV (struct Lisp_Symbol *sym)
eassume (sym->u.s.redirect == SYMBOL_LOCALIZED && sym->u.s.val.blv);
return sym->u.s.val.blv;
}
INLINE union Lisp_Fwd *
INLINE lispfwd
SYMBOL_FWD (struct Lisp_Symbol *sym)
{
eassume (sym->u.s.redirect == SYMBOL_FORWARDED && sym->u.s.val.fwd);
eassume (sym->u.s.redirect == SYMBOL_FORWARDED && sym->u.s.val.fwd.fwdptr);
return sym->u.s.val.fwd;
}
@ -2197,10 +2204,10 @@ SET_SYMBOL_BLV (struct Lisp_Symbol *sym, struct Lisp_Buffer_Local_Value *v)
sym->u.s.val.blv = v;
}
INLINE void
SET_SYMBOL_FWD (struct Lisp_Symbol *sym, union Lisp_Fwd *v)
SET_SYMBOL_FWD (struct Lisp_Symbol *sym, void *v)
{
eassume (sym->u.s.redirect == SYMBOL_FORWARDED && v);
sym->u.s.val.fwd = v;
sym->u.s.val.fwd.fwdptr = v;
}
INLINE Lisp_Object
@ -2727,7 +2734,7 @@ struct Lisp_Buffer_Local_Value
Presumably equivalent to (defcell!=valcell). */
bool_bf found : 1;
/* If non-NULL, a forwarding to the C var where it should also be set. */
union Lisp_Fwd *fwd; /* Should never be (Buffer|Kboard)_Objfwd. */
lispfwd fwd; /* Should never be (Buffer|Kboard)_Objfwd. */
/* The buffer for which the loaded binding was found. */
Lisp_Object where;
/* A cons cell that holds the default value. It has the form
@ -2749,32 +2756,24 @@ struct Lisp_Kboard_Objfwd
int offset;
};
union Lisp_Fwd
{
struct Lisp_Intfwd u_intfwd;
struct Lisp_Boolfwd u_boolfwd;
struct Lisp_Objfwd u_objfwd;
struct Lisp_Buffer_Objfwd u_buffer_objfwd;
struct Lisp_Kboard_Objfwd u_kboard_objfwd;
};
INLINE enum Lisp_Fwd_Type
XFWDTYPE (union Lisp_Fwd *a)
XFWDTYPE (lispfwd a)
{
return a->u_intfwd.type;
enum Lisp_Fwd_Type *p = a.fwdptr;
return *p;
}
INLINE bool
BUFFER_OBJFWDP (union Lisp_Fwd *a)
BUFFER_OBJFWDP (lispfwd a)
{
return XFWDTYPE (a) == Lisp_Fwd_Buffer_Obj;
}
INLINE struct Lisp_Buffer_Objfwd *
XBUFFER_OBJFWD (union Lisp_Fwd *a)
XBUFFER_OBJFWD (lispfwd a)
{
eassert (BUFFER_OBJFWDP (a));
return &a->u_buffer_objfwd;
return a.fwdptr;
}
/* Lisp floating point type. */
@ -3552,7 +3551,7 @@ extern _Noreturn void args_out_of_range (Lisp_Object, Lisp_Object);
extern _Noreturn void args_out_of_range_3 (Lisp_Object, Lisp_Object,
Lisp_Object);
extern _Noreturn void circular_list (Lisp_Object);
extern Lisp_Object do_symval_forwarding (union Lisp_Fwd *);
extern Lisp_Object do_symval_forwarding (lispfwd);
enum Set_Internal_Bind {
SET_INTERNAL_SET,
SET_INTERNAL_BIND,

8
src/lread.c
View file

@ -4434,7 +4434,7 @@ defvar_int (struct Lisp_Intfwd *i_fwd,
i_fwd->intvar = address;
XSYMBOL (sym)->u.s.declared_special = true;
XSYMBOL (sym)->u.s.redirect = SYMBOL_FORWARDED;
SET_SYMBOL_FWD (XSYMBOL (sym), (union Lisp_Fwd *)i_fwd);
SET_SYMBOL_FWD (XSYMBOL (sym), i_fwd);
}
/* Similar but define a variable whose value is t if address contains 1,
@ -4449,7 +4449,7 @@ defvar_bool (struct Lisp_Boolfwd *b_fwd,
b_fwd->boolvar = address;
XSYMBOL (sym)->u.s.declared_special = true;
XSYMBOL (sym)->u.s.redirect = SYMBOL_FORWARDED;
SET_SYMBOL_FWD (XSYMBOL (sym), (union Lisp_Fwd *)b_fwd);
SET_SYMBOL_FWD (XSYMBOL (sym), b_fwd);
Vbyte_boolean_vars = Fcons (sym, Vbyte_boolean_vars);
}
@ -4468,7 +4468,7 @@ defvar_lisp_nopro (struct Lisp_Objfwd *o_fwd,
o_fwd->objvar = address;
XSYMBOL (sym)->u.s.declared_special = true;
XSYMBOL (sym)->u.s.redirect = SYMBOL_FORWARDED;
SET_SYMBOL_FWD (XSYMBOL (sym), (union Lisp_Fwd *)o_fwd);
SET_SYMBOL_FWD (XSYMBOL (sym), o_fwd);
}
void
@ -4492,7 +4492,7 @@ defvar_kboard (struct Lisp_Kboard_Objfwd *ko_fwd,
ko_fwd->offset = offset;
XSYMBOL (sym)->u.s.declared_special = true;
XSYMBOL (sym)->u.s.redirect = SYMBOL_FORWARDED;
SET_SYMBOL_FWD (XSYMBOL (sym), (union Lisp_Fwd *)ko_fwd);
SET_SYMBOL_FWD (XSYMBOL (sym), ko_fwd);
}
/* Check that the elements of lpath exist. */

26
src/pdumper.c
View file

@ -2334,32 +2334,30 @@ dump_fwd_kboard_obj (struct dump_context *ctx,
}
static dump_off
dump_fwd (struct dump_context *ctx, union Lisp_Fwd *fwd)
dump_fwd (struct dump_context *ctx, lispfwd fwd)
{
#if CHECK_STRUCTS && !defined (HASH_Lisp_Fwd_5227B18E87)
# error "Lisp_Fwd changed. See CHECK_STRUCTS comment."
#endif
#if CHECK_STRUCTS && !defined (HASH_Lisp_Fwd_Type_9CBA6EE55E)
# error "Lisp_Fwd_Type changed. See CHECK_STRUCTS comment."
#endif
void const *p = fwd.fwdptr;
dump_off offset;
switch (XFWDTYPE (fwd))
{
case Lisp_Fwd_Int:
offset = dump_fwd_int (ctx, &fwd->u_intfwd);
offset = dump_fwd_int (ctx, p);
break;
case Lisp_Fwd_Bool:
offset = dump_fwd_bool (ctx, &fwd->u_boolfwd);
offset = dump_fwd_bool (ctx, p);
break;
case Lisp_Fwd_Obj:
offset = dump_fwd_obj (ctx, &fwd->u_objfwd);
offset = dump_fwd_obj (ctx, p);
break;
case Lisp_Fwd_Buffer_Obj:
offset = dump_fwd_buffer_obj (ctx, &fwd->u_buffer_objfwd);
offset = dump_fwd_buffer_obj (ctx, p);
break;
case Lisp_Fwd_Kboard_Obj:
offset = dump_fwd_kboard_obj (ctx, &fwd->u_kboard_objfwd);
offset = dump_fwd_kboard_obj (ctx, p);
break;
default:
emacs_abort ();
@ -2372,20 +2370,20 @@ static dump_off
dump_blv (struct dump_context *ctx,
const struct Lisp_Buffer_Local_Value *blv)
{
#if CHECK_STRUCTS && !defined (HASH_Lisp_Buffer_Local_Value_066F33A92E)
#if CHECK_STRUCTS && !defined HASH_Lisp_Buffer_Local_Value_3C363FAC3C
# error "Lisp_Buffer_Local_Value changed. See CHECK_STRUCTS comment."
#endif
struct Lisp_Buffer_Local_Value out;
dump_object_start (ctx, &out, sizeof (out));
DUMP_FIELD_COPY (&out, blv, local_if_set);
DUMP_FIELD_COPY (&out, blv, found);
if (blv->fwd)
dump_field_fixup_later (ctx, &out, blv, &blv->fwd);
if (blv->fwd.fwdptr)
dump_field_fixup_later (ctx, &out, blv, &blv->fwd.fwdptr);
dump_field_lv (ctx, &out, blv, &blv->where, WEIGHT_NORMAL);
dump_field_lv (ctx, &out, blv, &blv->defcell, WEIGHT_STRONG);
dump_field_lv (ctx, &out, blv, &blv->valcell, WEIGHT_STRONG);
dump_off offset = dump_object_finish (ctx, &out, sizeof (out));
if (blv->fwd)
if (blv->fwd.fwdptr)
dump_remember_fixup_ptr_raw
(ctx,
offset + dump_offsetof (struct Lisp_Buffer_Local_Value, fwd),
@ -2437,7 +2435,7 @@ dump_symbol (struct dump_context *ctx,
Lisp_Object object,
dump_off offset)
{
#if CHECK_STRUCTS && !defined (HASH_Lisp_Symbol_60EA1E748E)
#if CHECK_STRUCTS && !defined HASH_Lisp_Symbol_999DC26DEC
# error "Lisp_Symbol changed. See CHECK_STRUCTS comment."
#endif
#if CHECK_STRUCTS && !defined (HASH_symbol_redirect_ADB4F5B113)