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Diffstat (limited to 'src/ChangeLog')
| -rw-r--r-- | src/ChangeLog | 55 |
1 files changed, 55 insertions, 0 deletions
diff --git a/src/ChangeLog b/src/ChangeLog index e6a9f9c69f..e1548e9a09 100644 --- a/src/ChangeLog +++ b/src/ChangeLog @@ -1,3 +1,58 @@ +2011-04-25 Paul Eggert <[email protected]> + + 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. + 2011-04-24 Paul Eggert <[email protected]> * bytecode.c (exec_byte_code): Don't use XVECTOR before CHECK_VECTOR. |