Commit 6b08ad52 authored by Paul Eggert's avatar Paul Eggert

Fix alignment portability problems

Do not assume that the natural alignment of Lisp objects is a
multiple of GCALIGNMENT.  This improves on the portability of the
recent fix for Bug#29040.
* lib-src/make-docfile.c (close_emacs_globals):
* src/buffer.c (buffer_defaults, buffer_local_symbols):
* src/lisp.h (DEFUN):
* src/thread.c (main_thread):
Use GCALIGNED, not alignas (GCALIGNMENT).
* src/alloc.c (COMMON_MULTIPLE):
Move back here from lisp.h, since it is no longer used elsewhere.
* src/lisp.h (GCALIGNMENT): No longer a macro, since we need not
worry about MSVC.  Omit no-longer-needed consistency check.
* src/thread.c (THREAD_ALIGNMENT): Remove.
parent a9f8706f
......@@ -668,7 +668,7 @@ close_emacs_globals (ptrdiff_t num_symbols)
"extern\n"
"#endif\n"
"struct {\n"
" struct Lisp_Symbol alignas (GCALIGNMENT) s;\n"
" struct Lisp_Symbol GCALIGNED s;\n"
"} lispsym[%td];\n"),
num_symbols);
}
......
......@@ -621,6 +621,12 @@ buffer_memory_full (ptrdiff_t nbytes)
#endif
}
/* A common multiple of the positive integers A and B. Ideally this
would be the least common multiple, but there's no way to do that
as a constant expression in C, so do the best that we can easily do. */
#define COMMON_MULTIPLE(a, b) \
((a) % (b) == 0 ? (a) : (b) % (a) == 0 ? (b) : (a) * (b))
#ifndef XMALLOC_OVERRUN_CHECK
#define XMALLOC_OVERRUN_CHECK_OVERHEAD 0
#else
......
......@@ -61,7 +61,7 @@ struct buffer *all_buffers;
Setting the default value also goes through the alist of buffers
and stores into each buffer that does not say it has a local value. */
struct buffer alignas (GCALIGNMENT) buffer_defaults;
struct buffer GCALIGNED buffer_defaults;
/* This structure marks which slots in a buffer have corresponding
default values in buffer_defaults.
......@@ -84,7 +84,7 @@ struct buffer buffer_local_flags;
/* This structure holds the names of symbols whose values may be
buffer-local. It is indexed and accessed in the same way as the above. */
struct buffer alignas (GCALIGNMENT) buffer_local_symbols;
struct buffer GCALIGNED buffer_local_symbols;
/* Return the symbol of the per-buffer variable at offset OFFSET in
the buffer structure. */
......
......@@ -228,14 +228,12 @@ extern bool suppress_checking EXTERNALLY_VISIBLE;
USE_LSB_TAG not only requires the least 3 bits of pointers returned by
malloc to be 0 but also needs to be able to impose a mult-of-8 alignment
on the few static Lisp_Objects used: lispsym, all the defsubr, and
the two special buffers buffer_defaults and buffer_local_symbols. */
on the few static Lisp_Objects used, all of which are aligned via
the GCALIGN macro defined below. */
enum Lisp_Bits
{
/* 2**GCTYPEBITS. This must be a macro that expands to a literal
integer constant, for MSVC. */
#define GCALIGNMENT 8
GCALIGNMENT = 1 << GCTYPEBITS,
/* Number of bits in a Lisp_Object value, not counting the tag. */
VALBITS = EMACS_INT_WIDTH - GCTYPEBITS,
......@@ -247,10 +245,6 @@ enum Lisp_Bits
FIXNUM_BITS = VALBITS + 1
};
#if GCALIGNMENT != 1 << GCTYPEBITS
# error "GCALIGNMENT and GCTYPEBITS are inconsistent"
#endif
/* The maximum value that can be stored in a EMACS_INT, assuming all
bits other than the type bits contribute to a nonnegative signed value.
This can be used in #if, e.g., '#if USE_LSB_TAG' below expands to an
......@@ -277,18 +271,15 @@ DEFINE_GDB_SYMBOL_END (VALMASK)
error !;
#endif
/* Declare an object to have an address that is a multiple of
GCALIGNMENT. alignas is not suitable here, as it fails if the
object's natural alignment exceeds GCALIGNMENT. */
#ifdef HAVE_STRUCT_ATTRIBUTE_ALIGNED
# define GCALIGNED __attribute__ ((aligned (GCALIGNMENT)))
#else
# define GCALIGNED /* empty */
#endif
/* A common multiple of the positive integers A and B. Ideally this
would be the least common multiple, but there's no way to do that
as a constant expression in C, so do the best that we can easily do. */
#define COMMON_MULTIPLE(a, b) \
((a) % (b) == 0 ? (a) : (b) % (a) == 0 ? (b) : (a) * (b))
/* Some operations are so commonly executed that they are implemented
as macros, not functions, because otherwise runtime performance would
suffer too much when compiling with GCC without optimization.
......@@ -2946,7 +2937,7 @@ CHECK_NUMBER_CDR (Lisp_Object x)
#ifdef _MSC_VER
#define DEFUN(lname, fnname, sname, minargs, maxargs, intspec, doc) \
Lisp_Object fnname DEFUN_ARGS_ ## maxargs ; \
static struct Lisp_Subr alignas (GCALIGNMENT) sname = \
static struct Lisp_Subr GCALIGNED sname = \
{ { (PVEC_SUBR << PSEUDOVECTOR_AREA_BITS) \
| (sizeof (struct Lisp_Subr) / sizeof (EMACS_INT)) }, \
{ (Lisp_Object (__cdecl *)(void))fnname }, \
......@@ -2954,7 +2945,7 @@ CHECK_NUMBER_CDR (Lisp_Object x)
Lisp_Object fnname
#else /* not _MSC_VER */
#define DEFUN(lname, fnname, sname, minargs, maxargs, intspec, doc) \
static struct Lisp_Subr alignas (GCALIGNMENT) sname = \
static struct Lisp_Subr GCALIGNED sname = \
{ { PVEC_SUBR << PSEUDOVECTOR_AREA_BITS }, \
{ .a ## maxargs = fnname }, \
minargs, maxargs, lname, intspec, 0}; \
......
......@@ -26,9 +26,7 @@ along with GNU Emacs. If not, see <https://www.gnu.org/licenses/>. */
#include "coding.h"
#include "syssignal.h"
#define THREAD_ALIGNMENT COMMON_MULTIPLE (alignof (max_align_t), GCALIGNMENT)
static struct thread_state alignas (THREAD_ALIGNMENT) main_thread;
static struct thread_state GCALIGNED main_thread;
struct thread_state *current_thread = &main_thread;
......
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