From c92462e52433c422d41c5e5aa177f9513eb517e3 Mon Sep 17 00:00:00 2001 From: Paul Eggert
Date: Fri, 10 Nov 2017 17:37:50 -0800 Subject: [PATCH 1/2] Change vectorlike from struct to union * src/lisp.h (vectorlike_headed): Change from struct to union. All uses changed. Since it has only one member, this does not change semantics. This is designed to simplify future changes needed to fix bugs like Bug#29040. All uses changed. --- doc/lispref/internals.texi | 4 ++-- src/buffer.h | 2 +- src/font.h | 6 +++--- src/frame.h | 2 +- src/lisp.h | 28 ++++++++++++++-------------- src/process.h | 2 +- src/termhooks.h | 2 +- src/thread.h | 6 +++--- src/w32term.h | 2 +- src/window.c | 8 ++++---- src/window.h | 2 +- src/xterm.h | 2 +- src/xwidget.h | 4 ++-- 13 files changed, 35 insertions(+), 35 deletions(-) diff --git a/doc/lispref/internals.texi b/doc/lispref/internals.texi index 663d0fd92b..b0348e74d4 100644 --- a/doc/lispref/internals.texi +++ b/doc/lispref/internals.texi @@ -248,7 +248,7 @@ Garbage Collection @cindex storage of vector-like Lisp objects Beyond the basic vector, a lot of objects like window, buffer, and frame are managed as if they were vectors. The corresponding C data -structures include the @code{struct vectorlike_header} field whose +structures include the @code{union vectorlike_header} field whose @code{size} member contains the subtype enumerated by @code{enum pvec_type} and an information about how many @code{Lisp_Object} fields this structure contains and what the size of the rest data is. This information is @@ -1085,7 +1085,7 @@ Buffer Internals @table @code @item header -A header of type @code{struct vectorlike_header} is common to all +A header of type @code{union vectorlike_header} is common to all vectorlike objects. @item own_text diff --git a/src/buffer.h b/src/buffer.h index ac7c5a5467..46c7c6e5ad 100644 --- a/src/buffer.h +++ b/src/buffer.h @@ -504,7 +504,7 @@ struct buffer_text struct buffer { - struct vectorlike_header header; + union vectorlike_header header; /* The name of this buffer. */ Lisp_Object name_; diff --git a/src/font.h b/src/font.h index 8f2e27f0ed..43d6f67e3e 100644 --- a/src/font.h +++ b/src/font.h @@ -244,7 +244,7 @@ enum font_property_index struct font_spec { - struct vectorlike_header header; + union vectorlike_header header; Lisp_Object props[FONT_SPEC_MAX]; }; @@ -252,7 +252,7 @@ struct font_spec struct font_entity { - struct vectorlike_header header; + union vectorlike_header header; Lisp_Object props[FONT_ENTITY_MAX]; }; @@ -265,7 +265,7 @@ struct font_entity struct font { - struct vectorlike_header header; + union vectorlike_header header; /* All Lisp_Object components must come first. That ensures they are all aligned normally. */ diff --git a/src/frame.h b/src/frame.h index e610fc768d..a3b7763643 100644 --- a/src/frame.h +++ b/src/frame.h @@ -79,7 +79,7 @@ enum ns_appearance_type struct frame { - struct vectorlike_header header; + union vectorlike_header header; /* All Lisp_Object components must come first. That ensures they are all aligned normally. */ diff --git a/src/lisp.h b/src/lisp.h index 015346858b..1d6fd5a4fe 100644 --- a/src/lisp.h +++ b/src/lisp.h @@ -796,11 +796,11 @@ struct Lisp_Symbol /* Header of vector-like objects. This documents the layout constraints on vectors and pseudovectors (objects of PVEC_xxx subtype). It also prevents compilers from being fooled by Emacs's type punning: XSETPSEUDOVECTOR - and PSEUDOVECTORP cast their pointers to struct vectorlike_header *, + and PSEUDOVECTORP cast their pointers to union vectorlike_header *, because when two such pointers potentially alias, a compiler won't incorrectly reorder loads and stores to their size fields. See Bug#8546. */ -struct vectorlike_header +union vectorlike_header { /* The only field contains various pieces of information: - The MSB (ARRAY_MARK_FLAG) holds the gcmarkbit. @@ -1094,10 +1094,10 @@ INLINE bool | ((restsize) << PSEUDOVECTOR_SIZE_BITS) \ | (lispsize))) -/* The cast to struct vectorlike_header * avoids aliasing issues. */ +/* The cast to union vectorlike_header * avoids aliasing issues. */ #define XSETPSEUDOVECTOR(a, b, code) \ XSETTYPED_PSEUDOVECTOR (a, b, \ - (((struct vectorlike_header *) \ + (((union vectorlike_header *) \ XUNTAG (a, Lisp_Vectorlike)) \ ->size), \ code) @@ -1399,7 +1399,7 @@ STRING_SET_CHARS (Lisp_Object string, ptrdiff_t newsize) struct Lisp_Vector { - struct vectorlike_header header; + union vectorlike_header header; Lisp_Object contents[FLEXIBLE_ARRAY_MEMBER]; }; @@ -1456,7 +1456,7 @@ PSEUDOVECTOR_TYPE (struct Lisp_Vector *v) /* Can't be used with PVEC_NORMAL_VECTOR. */ INLINE bool -PSEUDOVECTOR_TYPEP (struct vectorlike_header *a, enum pvec_type code) +PSEUDOVECTOR_TYPEP (union vectorlike_header *a, enum pvec_type code) { /* We don't use PSEUDOVECTOR_TYPE here so as to avoid a shift * operation when `code' is known. */ @@ -1472,8 +1472,8 @@ PSEUDOVECTORP (Lisp_Object a, int code) return false; else { - /* Converting to struct vectorlike_header * avoids aliasing issues. */ - struct vectorlike_header *h = XUNTAG (a, Lisp_Vectorlike); + /* Converting to union vectorlike_header * avoids aliasing issues. */ + union vectorlike_header *h = XUNTAG (a, Lisp_Vectorlike); return PSEUDOVECTOR_TYPEP (h, code); } } @@ -1484,7 +1484,7 @@ struct Lisp_Bool_Vector { /* HEADER.SIZE is the vector's size field. It doesn't have the real size, just the subtype information. */ - struct vectorlike_header header; + union vectorlike_header header; /* This is the size in bits. */ EMACS_INT size; /* The actual bits, packed into bytes. @@ -1697,7 +1697,7 @@ struct Lisp_Char_Table pseudovector type information. It holds the size, too. The size counts the defalt, parent, purpose, ascii, contents, and extras slots. */ - struct vectorlike_header header; + union vectorlike_header header; /* This holds a default value, which is used whenever the value for a specific character is nil. */ @@ -1739,7 +1739,7 @@ struct Lisp_Sub_Char_Table { /* HEADER.SIZE is the vector's size field, which also holds the pseudovector type information. It holds the size, too. */ - struct vectorlike_header header; + union vectorlike_header header; /* Depth of this sub char-table. It should be 1, 2, or 3. A sub char-table of depth 1 contains 16 elements, and each element @@ -1814,7 +1814,7 @@ CHAR_TABLE_SET (Lisp_Object ct, int idx, Lisp_Object val) struct Lisp_Subr { - struct vectorlike_header header; + union vectorlike_header header; union { Lisp_Object (*a0) (void); Lisp_Object (*a1) (Lisp_Object); @@ -2026,7 +2026,7 @@ struct hash_table_test struct Lisp_Hash_Table { /* This is for Lisp; the hash table code does not refer to it. */ - struct vectorlike_header header; + union vectorlike_header header; /* Nil if table is non-weak. Otherwise a symbol describing the weakness of the table. */ @@ -3929,7 +3929,7 @@ typedef emacs_value (*emacs_subr) (emacs_env *, ptrdiff_t, struct Lisp_Module_Function { - struct vectorlike_header header; + union vectorlike_header header; /* Fields traced by GC; these must come first. */ Lisp_Object documentation; diff --git a/src/process.h b/src/process.h index 5a044f669f..5670f44736 100644 --- a/src/process.h +++ b/src/process.h @@ -41,7 +41,7 @@ enum { PROCESS_OPEN_FDS = 6 }; struct Lisp_Process { - struct vectorlike_header header; + union vectorlike_header header; /* Name of subprocess terminal. */ Lisp_Object tty_name; diff --git a/src/termhooks.h b/src/termhooks.h index dd6044aabd..fe4e993c96 100644 --- a/src/termhooks.h +++ b/src/termhooks.h @@ -373,7 +373,7 @@ extern struct tty_display_info *gpm_tty; struct terminal { /* This is for Lisp; the terminal code does not refer to it. */ - struct vectorlike_header header; + union vectorlike_header header; /* Parameter alist of this terminal. */ Lisp_Object param_alist; diff --git a/src/thread.h b/src/thread.h index 19baafbf8a..1845974bc2 100644 --- a/src/thread.h +++ b/src/thread.h @@ -35,7 +35,7 @@ along with GNU Emacs. If not, see