[Emacs-diffs] trunk r117897: Port USE_LOCAL_ALLOCATORS code to clang 3.4 x86-64.

[Paul Eggert]

------------------------------------------------------------
revno: 117897
revision-id: address@hidden
parent: address@hidden
committer: Paul Eggert <address@hidden>
branch nick: trunk
timestamp: Wed 2014-09-17 18:03:40 -0700
message:
  Port USE_LOCAL_ALLOCATORS code to clang 3.4 x86-64.
  
  * lisp.h (ALLOCA_FIXUP): New constant.
  (LOCAL_ALLOCA): New macro.
  (local_cons, make_local_vector, make_local_string): Use them.
  (local_cons): Rename parameter to make capture less likely.
modified:
  src/ChangeLog                  changelog-20091113204419-o5vbwnq5f7feedwu-1438
  src/lisp.h                     lisp.h-20091113204419-o5vbwnq5f7feedwu-253

=== modified file 'src/ChangeLog'
--- a/src/ChangeLog     2014-09-17 19:58:31 +0000
+++ b/src/ChangeLog     2014-09-18 01:03:40 +0000
@@ -1,3 +1,11 @@
+2014-09-18  Paul Eggert  <address@hidden>
+
+       Port USE_LOCAL_ALLOCATORS code to clang 3.4 x86-64.
+       * lisp.h (ALLOCA_FIXUP): New constant.
+       (LOCAL_ALLOCA): New macro.
+       (local_cons, make_local_vector, make_local_string): Use them.
+       (local_cons): Rename parameter to make capture less likely.
+
 2014-09-17  Samuel Bronson  <address@hidden>
 
        * unexmacosx.c (copy_data_segment): Port to GCC 4.6+ (Bug#9927).

=== modified file 'src/lisp.h'
--- a/src/lisp.h        2014-09-17 18:27:36 +0000
+++ b/src/lisp.h        2014-09-18 01:03:40 +0000
@@ -4603,14 +4603,29 @@
 
 # define USE_LOCAL_ALLOCATORS
 
+/* Alignment fixup needed for alloca.  GCC aligns alloca properly already,
+   Clang sometimes doesn't, and play it safe for other random compilers.  */
+# if __GNUC__ && !__clang__
+enum { ALLOCA_FIXUP = 0 };
+# else
+enum { ALLOCA_FIXUP = GCALIGNMENT - 1 };
+# endif
+
+/* Declare a void * variable PTR and set it to a properly-aligned array of
+   N newly allocated bytes with function lifetime.  */
+# define LOCAL_ALLOCA(ptr, n)                          \
+    void *ptr = alloca ((n) + ALLOCA_FIXUP);           \
+    ptr = (void *) ((intptr_t) ptr_ & ~(ALLOCA_FIXUP))
+
 /* Return a function-scoped cons whose car is X and cdr is Y.  */
 
 # define local_cons(x, y)                                              \
     ({                                                                 \
-       struct Lisp_Cons *c = alloca (sizeof (struct Lisp_Cons));       \
-       c->car = (x);                                                   \
-       c->u.cdr = (y);                                                 \
-       make_lisp_ptr (c, Lisp_Cons);                                   \
+       LOCAL_ALLOCA (ptr_, sizeof (struct Lisp_Cons));                 \
+       struct Lisp_Cons *c_ = ptr_;                                    \
+       c_->car = (x);                                                  \
+       c_->u.cdr = (y);                                                        
\
+       make_lisp_ptr (c_, Lisp_Cons);                                  \
     })
 
 # define local_list1(x) local_cons (x, Qnil)
@@ -4625,9 +4640,9 @@
        ptrdiff_t size_ = size;                                         \
        Lisp_Object init_ = init;                                       \
        Lisp_Object vec_;                                               \
-       if (size_ <= (MAX_ALLOCA - header_size) / word_size)            \
+       if (size_ <= (MAX_ALLOCA - ALLOCA_FIXUP - header_size) / word_size) \
         {                                                              \
-          void *ptr_ = alloca (size_ * word_size + header_size);       \
+          LOCAL_ALLOCA (ptr_, size_ * word_size + header_size);        \
           vec_ = local_vector_init (ptr_, size_, init_);               \
         }                                                              \
        else                                                            \
@@ -4642,10 +4657,10 @@
        char const *data_ = data;                                       \
        ptrdiff_t nbytes_ = nbytes;                                     \
        Lisp_Object string_;                                            \
-       if (nbytes_ <= MAX_ALLOCA - sizeof (struct Lisp_String) - 1)    \
+       if (nbytes_                                                     \
+          <= MAX_ALLOCA - ALLOCA_FIXUP - sizeof (struct Lisp_String) - 1) \
         {                                                              \
-          struct Lisp_String *ptr_                                     \
-            = alloca (sizeof (struct Lisp_String) + 1 + nbytes_);      \
+          LOCAL_ALLOCA (ptr_, sizeof (struct Lisp_String) + 1 + bytes_); \
           string_ = local_string_init (ptr_, data_, nbytes_);          \
         }                                                              \
        else                                                            \