• Eli Zaretskii's avatar
    Backport revisions... · 14fe7b53
    Eli Zaretskii authored
    Backport revisions 2011-04-24T05:30:24Z!eggert@cs.ucla.edu..2011-04-25T19:40:22Z!eggert@cs.ucla.edu (inclusive) from trunk (bug#8623)
    
    	The next log entry shows the actual changes by Paul Eggert.
    
     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.
     src/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.
     src/lisp.h: Say "vectorlike header" rather than "vector header.
     (struct vectorlike_header): Rename from struct vector_header.
     (XVECTORLIKE_HEADER_SIZE): Renamed from XVECTOR_HEADER_SIZE.
     All uses changed.
     (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.
     src/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".
     src/buffer.h (struct buffer): Likewise.
     src/font.h (struct font_spec, struct font_entity, struct font): Likewise.
     src/frame.h (struct frame): Likewise.
     src/process.h (struct Lisp_Process): Likewise.
     src/termhooks.h (struct terminal): Likewise.
     src/window.c (struct save_window_data, struct saved_window): Likewise.
     src/window.h (struct window): Likewise.
     src/alloc.c (allocate_buffer, Fmake_bool_vector, allocate_pseudovector):
     Use XSETPVECTYPESIZE, not XSETPVECTYPE, to avoid aliasing problems.
     src/buffer.c (init_buffer_once): Likewise.
     src/lread.c (defsubr): Use XSETTYPED_PVECTYPE, since Lisp_Subr is a
     special case.
     src/process.c (Fformat_network_address): Use local var for size,
     for brevity.
     src/fns.c (vector): Remove; this old hack is no longer needed.
     src/bytecode.c (exec_byte_code): Don't use XVECTOR before CHECK_VECTOR.
    14fe7b53
window.c 225 KB