diff options
author | Paul Eggert <[email protected]> | 2011-04-25 00:14:46 -0700 |
---|---|---|
committer | Paul Eggert <[email protected]> | 2011-04-25 00:14:46 -0700 |
commit | eab3844f965646b62e242aa622754b86d1fd3444 (patch) | |
tree | 10246105e5facc5d61ccf797dfa05debdb1877c1 /src/buffer.c | |
parent | 0df1eac54fdf82a80a7611fe421d94a23ebd4a0a (diff) |
lisp.h: Fix a problem with aliasing and vector headers.
GCC 4.6.0 optimizes based on type-based alias analysis. For
example, if b is of type struct buffer * and v of type struct
Lisp_Vector *, then gcc -O2 was incorrectly assuming that &b->size
!= &v->size, and therefore "v->size = 1; b->size = 2; return
v->size;" must therefore return 1. This assumption is incorrect
for Emacs, since it type-puns struct Lisp_Vector * with many other
types. To fix this problem, this patch adds a new type struct
vector_header that documents the constraints on layout of vectors
and pseudovectors, and helps optimizing compilers not get fooled
by Emacs's type punning. It also adds the macros XSETTYPED_PVECTYPE
XSETTYPED_PSEUDOVECTOR, TYPED_PSEUDOVECTORP, for similar reasons.
* lisp.h (XVECTOR_SIZE): New convenience macro. All previous uses of
XVECTOR (foo)->size replaced to use this macro, to avoid the hassle
of writing XVECTOR (foo)->header.size.
(XVECTOR_HEADER_SIZE): New macro, for use in XSETPSEUDOVECTOR.
(XSETTYPED_PVECTYPE): New macro, specifying the name of the size
member.
(XSETPVECTYPE): Rewrite in terms of new macro.
(XSETPVECTYPESIZE): New macro, specifying both type and size.
This is a bit clearer, and further avoids the possibility of
undesirable aliasing.
(XSETTYPED_PSEUDOVECTOR): New macro, specifying the size.
(XSETPSEUDOVECTOR): Rewrite in terms of XSETTYPED_PSEUDOVECTOR
and XVECTOR_HEADER_SIZE.
(XSETSUBR): Rewrite in terms of XSETTYPED_PSEUDOVECTOR and XSIZE,
since Lisp_Subr is a special case (no "next" field).
(ASIZE): Rewrite in terms of XVECTOR_SIZE.
(struct vector_header): New type.
(TYPED_PSEUDOVECTORP): New macro, also specifying the C type of the
object, to help avoid aliasing.
(PSEUDOVECTORP): Rewrite in terms of TYPED_PSEUDOVECTORP.
(SUBRP): Likewise, since Lisp_Subr is a special case.
* lisp.h (struct Lisp_Vector, struct Lisp_Char_Table):
(struct Lisp_Sub_Char_Table, struct Lisp_Bool_Vector):
(struct Lisp_Hash_Table): Combine first two members into a single
struct vector_header member. All uses of "size" and "next" members
changed to be "header.size" and "header.next".
* buffer.h (struct buffer): Likewise.
* font.h (struct font_spec, struct font_entity, struct font): Likewise.
* frame.h (struct frame): Likewise.
* process.h (struct Lisp_Process): Likewise.
* termhooks.h (struct terminal): Likewise.
* window.c (struct save_window_data, struct saved_window): Likewise.
* window.h (struct window): Likewise.
* alloc.c (allocate_buffer, Fmake_bool_vector, allocate_pseudovector):
Use XSETPVECTYPESIZE, not XSETPVECTYPE, to avoid aliasing problems.
* buffer.c (init_buffer_once): Likewise.
* lread.c (defsubr): Use XSETTYPED_PVECTYPE, since Lisp_Subr is a
special case.
* process.c (Fformat_network_address): Use local var for size,
for brevity.
Diffstat (limited to 'src/buffer.c')
-rw-r--r-- | src/buffer.c | 18 |
1 files changed, 9 insertions, 9 deletions
diff --git a/src/buffer.c b/src/buffer.c index c649836adb..6ced4fbae8 100644 --- a/src/buffer.c +++ b/src/buffer.c @@ -43,7 +43,7 @@ along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>. */ struct buffer *current_buffer; /* the current buffer */ /* First buffer in chain of all buffers (in reverse order of creation). - Threaded through ->next. */ + Threaded through ->header.next. */ struct buffer *all_buffers; @@ -359,7 +359,7 @@ even if it is dead. The return value is never nil. */) b->prevent_redisplay_optimizations_p = 1; /* Put this on the chain of all buffers including killed ones. */ - b->next = all_buffers; + b->header.next.buffer = all_buffers; all_buffers = b; /* An ordinary buffer normally doesn't need markers @@ -588,7 +588,7 @@ CLONE nil means the indirect buffer's state is reset to default values. */) BVAR (b, width_table) = Qnil; /* Put this on the chain of all buffers including killed ones. */ - b->next = all_buffers; + b->header.next.buffer = all_buffers; all_buffers = b; name = Fcopy_sequence (name); @@ -1458,7 +1458,7 @@ with SIGHUP. */) GCPRO1 (buffer); - for (other = all_buffers; other; other = other->next) + for (other = all_buffers; other; other = other->header.next.buffer) /* all_buffers contains dead buffers too; don't re-kill them. */ if (other->base_buffer == b && !NILP (BVAR (other, name))) @@ -2099,7 +2099,7 @@ DEFUN ("buffer-swap-text", Fbuffer_swap_text, Sbuffer_swap_text, { /* This is probably harder to make work. */ struct buffer *other; - for (other = all_buffers; other; other = other->next) + for (other = all_buffers; other; other = other->header.next.buffer) if (other->base_buffer == other_buffer || other->base_buffer == current_buffer) error ("One of the buffers to swap has indirect buffers"); @@ -2476,7 +2476,7 @@ current buffer is cleared. */) /* Copy this buffer's new multibyte status into all of its indirect buffers. */ - for (other = all_buffers; other; other = other->next) + for (other = all_buffers; other; other = other->header.next.buffer) if (other->base_buffer == current_buffer && !NILP (BVAR (other, name))) { BVAR (other, enable_multibyte_characters) @@ -4178,7 +4178,7 @@ static int last_overlay_modification_hooks_used; static void add_overlay_mod_hooklist (Lisp_Object functionlist, Lisp_Object overlay) { - int oldsize = XVECTOR (last_overlay_modification_hooks)->size; + int oldsize = XVECTOR_SIZE (last_overlay_modification_hooks); if (last_overlay_modification_hooks_used == oldsize) last_overlay_modification_hooks = larger_vector @@ -4973,9 +4973,9 @@ init_buffer_once (void) buffer_local_symbols.text = &buffer_local_symbols.own_text; BUF_INTERVALS (&buffer_defaults) = 0; BUF_INTERVALS (&buffer_local_symbols) = 0; - XSETPVECTYPE (&buffer_defaults, PVEC_BUFFER); + XSETPVECTYPESIZE (&buffer_defaults, PVEC_BUFFER, 0); XSETBUFFER (Vbuffer_defaults, &buffer_defaults); - XSETPVECTYPE (&buffer_local_symbols, PVEC_BUFFER); + XSETPVECTYPESIZE (&buffer_local_symbols, PVEC_BUFFER, 0); XSETBUFFER (Vbuffer_local_symbols, &buffer_local_symbols); /* Set up the default values of various buffer slots. */ |