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.

1 files changed, 5 insertions, 16 deletions

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: