Use Gnulib stdalign and environ modules (Bug#9772, Bug#9960).

* .bzrignore: Add lib/stdalign.h.
* config.bat: Do not set NO_DECL_ALIGN; no longer needed.
Copy lib/stdalign.in.h to lib/stdalign.in-h as needed.
* configure.ac (HAVE_ATTRIBUTE_ALIGNED): Remove the code that
fiddles with this, as gnulib now does this for us.
* admin/merge-gnulib: Add environ, stdalign.
* m4/environ.m4: New file, from gnulib.
* lib/gnulib.mk, m4/gnulib-comp.m4: Regenerate.
* lib/stdalign.in.h, m4/stdalign.m4: New files, from gnulib.
* sed2v2.inp (HAVE_ATTRIBUTE_ALIGNED): Remove edit.
* sedlibmk.inp (STDALIGN_H, @GL_GENERATE_STDALIGN_H_TRUE@)
(GL_GENERATE_STDALIGN_H_FALSE): New edits.
* nt/config.nt (HAVE_ATTRIBUTE_ALIGNED): Remove.
* src/alloc.c (XMALLOC_BASE_ALIGNMENT, GC_POINTER_ALIGNMENT, pure_alloc):
Simplify by using alignof.
(pure_alloc) [! USE_LSB_TAG]: Don't over-align EMACS_INT values.
* src/lisp.h: Include <stdalign.h>.
(GCALIGNMENT): New macro and constant.
(DECL_ALIGN): Remove.  All uses replaced by alignas (GCALIGNMENT).
(USE_LSB_TAG): ifdef on alignas, not on DECL_ALIGN.
(stdalign): New macro, if not already defined.

4 files changed, 36 insertions, 47 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 6457fc2209b..cc112f4b5da 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,15 @@
+2012-07-28  Paul Eggert  <eggert@cs.ucla.edu>
+
+        Use Gnulib stdalign module (Bug#9772, Bug#9960).
+        * alloc.c (XMALLOC_BASE_ALIGNMENT, GC_POINTER_ALIGNMENT, pure_alloc):
+        Simplify by using alignof.
+        (pure_alloc) [! USE_LSB_TAG]: Don't over-align EMACS_INT values.
+        * lisp.h: Include <stdalign.h>.
+        (GCALIGNMENT): New macro and constant.
+        (DECL_ALIGN): Remove.  All uses replaced by alignas (GCALIGNMENT).
+        (USE_LSB_TAG): ifdef on alignas, not on DECL_ALIGN.
+        (stdalign): New macro, if not already defined.
+
 2012-07-28  Eli Zaretskii  <eliz@gnu.org>
 
         Fix non-ASCII input in non-GUI frames on MS-Windows.  (Bug#12055)
diff --git a/src/alloc.c b/src/alloc.c
index a551dd821b8..e5f412bb4c3 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -533,12 +533,7 @@ buffer_memory_full (ptrdiff_t nbytes)
    hold a size_t value and (2) the header size is a multiple of the
    alignment that Emacs needs for C types and for USE_LSB_TAG.  */
 #define XMALLOC_BASE_ALIGNMENT                          \
-  offsetof (                                            \
-    struct {                                            \
-      union { long double d; intmax_t i; void *p; } u;  \
-      char c;                                           \
-    },                                                  \
-    c)
+  alignof (union { long double d; intmax_t i; void *p; })
 
 #if USE_LSB_TAG
 # define XMALLOC_HEADER_ALIGNMENT \
@@ -4652,10 +4647,10 @@ mark_maybe_pointer (void *p)
 }
 
 
-/* Alignment of pointer values.  Use offsetof, as it sometimes returns
+/* Alignment of pointer values.  Use alignof, as it sometimes returns
    a smaller alignment than GCC's __alignof__ and mark_memory might
    miss objects if __alignof__ were used.  */
-#define GC_POINTER_ALIGNMENT offsetof (struct {char a; void *b;}, b)
+#define GC_POINTER_ALIGNMENT alignof (void *)
 
 /* Define POINTERS_MIGHT_HIDE_IN_OBJECTS to 1 if marking via C pointers does
    not suffice, which is the typical case.  A host where a Lisp_Object is
@@ -5103,17 +5098,11 @@ pure_alloc (size_t size, int type)
 #if USE_LSB_TAG
   size_t alignment = (1 << GCTYPEBITS);
 #else
-  size_t alignment = sizeof (EMACS_INT);
+  size_t alignment = alignof (EMACS_INT);
 
   /* Give Lisp_Floats an extra alignment.  */
   if (type == Lisp_Float)
-    {
-#if defined __GNUC__ && __GNUC__ >= 2
-      alignment = __alignof (struct Lisp_Float);
-#else
-      alignment = sizeof (struct Lisp_Float);
-#endif
-    }
+    alignment = alignof (struct Lisp_Float);
 #endif
 
  again:
diff --git a/src/buffer.c b/src/buffer.c
index 5e45882b892..70630de53cb 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -56,7 +56,7 @@ 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.  */
 
-DECL_ALIGN (struct buffer, buffer_defaults);
+struct buffer alignas (GCALIGNMENT) buffer_defaults;
 
 /* A Lisp_Object pointer to the above, used for staticpro */
 
@@ -83,7 +83,7 @@ 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. */
 
-DECL_ALIGN (struct buffer, buffer_local_symbols);
+struct buffer alignas (GCALIGNMENT) buffer_local_symbols;
 
 /* A Lisp_Object pointer to the above, used for staticpro */
 static Lisp_Object Vbuffer_local_symbols;
diff --git a/src/lisp.h b/src/lisp.h
index 80a9ab343c3..a45e9c2c892 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -20,6 +20,7 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #ifndef EMACS_LISP_H
 #define EMACS_LISP_H
 
+#include <stdalign.h>
 #include <stdarg.h>
 #include <stddef.h>
 #include <inttypes.h>
@@ -151,10 +152,6 @@ extern int suppress_checking EXTERNALLY_VISIBLE;
    on the few static Lisp_Objects used: all the defsubr as well
    as the two special buffers buffer_defaults and buffer_local_symbols.  */
 
-/* First, try and define DECL_ALIGN(type,var) which declares a static
-   variable VAR of type TYPE with the added requirement that it be
-   TYPEBITS-aligned.  */
-
 enum Lisp_Bits
   {
     /* Number of bits in a Lisp_Object tag.  This can be used in #if,
@@ -163,6 +160,12 @@ enum Lisp_Bits
 #define GCTYPEBITS 3
         GCTYPEBITS,
 
+    /* 2**GCTYPEBITS.  This must also be a macro that expands to a
+       literal integer constant, for MSVC.  */
+    GCALIGNMENT =
+#define GCALIGNMENT 8
+        GCALIGNMENT,
+
     /* Number of bits in a Lisp_Object value, not counting the tag.  */
     VALBITS = BITS_PER_EMACS_INT - GCTYPEBITS,
 
@@ -173,36 +176,22 @@ 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 VAL_MAX < UINTPTR_MAX' below.  */
 #define VAL_MAX (EMACS_INT_MAX >> (GCTYPEBITS - 1))
 
-#ifndef NO_DECL_ALIGN
-# ifndef DECL_ALIGN
-#  if HAVE_ATTRIBUTE_ALIGNED
-#   define DECL_ALIGN(type, var) \
-     type __attribute__ ((__aligned__ (1 << GCTYPEBITS))) var
-#  elif defined(_MSC_VER)
-#   define ALIGN_GCTYPEBITS 8
-#   if (1 << GCTYPEBITS) != ALIGN_GCTYPEBITS
-#    error ALIGN_GCTYPEBITS is wrong!
-#   endif
-#   define DECL_ALIGN(type, var) \
-     type __declspec(align(ALIGN_GCTYPEBITS)) var
-#  else
-     /* What directives do other compilers use?  */
-#  endif
-# endif
-#endif
-
 /* Unless otherwise specified, use USE_LSB_TAG on systems where:  */
 #ifndef USE_LSB_TAG
 /* 1.  We know malloc returns a multiple of 8.  */
 # if (defined GNU_MALLOC || defined DOUG_LEA_MALLOC || defined __GLIBC__ \
       || defined DARWIN_OS || defined __sun)
 /* 2.  We can specify multiple-of-8 alignment on static variables.  */
-#  ifdef DECL_ALIGN
+#  ifdef alignas
 /* 3.  Pointers-as-ints exceed VAL_MAX.
    On hosts where pointers-as-ints do not exceed VAL_MAX, USE_LSB_TAG is:
     a. unnecessary, because the top bits of an EMACS_INT are unused, and
@@ -223,12 +212,11 @@ enum enum_USE_LSB_TAG { USE_LSB_TAG = 0 };
 # define USE_LSB_TAG 0
 #endif
 
-/* If we cannot use 8-byte alignment, make DECL_ALIGN a no-op.  */
-#ifndef DECL_ALIGN
+#ifndef alignas
+# define alignas(alignment) /* empty */
 # if USE_LSB_TAG
-#  error "USE_LSB_TAG used without defining DECL_ALIGN"
+#  error "USE_LSB_TAG requires alignas"
 # endif
-# define DECL_ALIGN(type, var) type var
 #endif
 
 
@@ -1882,7 +1870,7 @@ typedef struct {
 #ifdef _MSC_VER
 #define DEFUN(lname, fnname, sname, minargs, maxargs, intspec, doc)     \
    Lisp_Object fnname DEFUN_ARGS_ ## maxargs ;                          \
-   static DECL_ALIGN (struct Lisp_Subr, sname) =                        \
+   static struct Lisp_Subr alignas (GCALIGNMENT) sname =                \
    { (PVEC_SUBR << PSEUDOVECTOR_SIZE_BITS)                              \
      | (sizeof (struct Lisp_Subr) / sizeof (EMACS_INT)),                \
       { (Lisp_Object (__cdecl *)(void))fnname },                        \
@@ -1891,7 +1879,7 @@ typedef struct {
 #else  /* not _MSC_VER */
 #define DEFUN(lname, fnname, sname, minargs, maxargs, intspec, doc)     \
    Lisp_Object fnname DEFUN_ARGS_ ## maxargs ;                          \
-   static DECL_ALIGN (struct Lisp_Subr, sname) =                        \
+   static struct Lisp_Subr alignas (GCALIGNMENT) sname =                \
      { PVEC_SUBR << PSEUDOVECTOR_SIZE_BITS,                             \
       { .a ## maxargs = fnname },                                       \
        minargs, maxargs, lname, intspec, 0};                            \