hppa: Fix type punning in sysdeps/hppa/dl-fptr.c [BZ 33888]

Compiling gcc with -Werror=strict-aliasing exposed a type punning
issue in dl-fptr.c.  It does a number of compare and swap operations
to atomically exchange function pointers, etc.  The PTR argument
is dereferenced to determine the type of the objects to exchange.
Casting the type of the PTR argument to a different type will
result in in an error with -Werror=strict-aliasing.  For example,
a `(ElfW(Addr) *' pointer is not strictly equivalent to a
`struct fdesc *' pointer.

Fix this by removing the casts from the COMPARE_AND_SWAP PTR
arguments and adjusting the type of the OLD and NEW arguments
to match the dereferenced PTR type.

Signed-off-by: John David Anglin <dave.anglin@bell.net>

diff --git a/sysdeps/hppa/dl-fptr.c b/sysdeps/hppa/dl-fptr.c
index ad755147cca2db83ab0c9589239901907c04347d..37def2eaed2caac852062684b5d9dbd7d60cab63 100644 (file)
--- a/sysdeps/hppa/dl-fptr.c
+++ b/sysdeps/hppa/dl-fptr.c
@@ -144,8 +144,8 @@ make_fdesc (ElfW(Addr) ip, ElfW(Addr) gp)
          if (fdesc == NULL)
            goto retry;
        }
-      while (! COMPARE_AND_SWAP ((ElfW(Addr) *) &l->free_list,
-                                (ElfW(Addr)) fdesc, fdesc->ip));
+      while (! COMPARE_AND_SWAP (&l->free_list, fdesc,
+                                (struct fdesc *) fdesc->ip));
     }
   else
     {
@@ -157,9 +157,7 @@ make_fdesc (ElfW(Addr) ip, ElfW(Addr) gp)
        goto retry;
 
       new_table->next = root;
-      if (! COMPARE_AND_SWAP ((ElfW(Addr) *) &l->root,
-                             (ElfW(Addr)) root,
-                             (ElfW(Addr)) new_table))
+      if (! COMPARE_AND_SWAP (&l->root, root, new_table))
        {
          /* Someone has just installed a new table. Return NULL to
             tell the caller to use the new table.  */
@@ -213,8 +211,7 @@ make_fptr_table (struct link_map *map)
     _dl_signal_error (errno, NULL, NULL,
                      N_("cannot map pages for fptr table"));
 
-  if (COMPARE_AND_SWAP ((ElfW(Addr) *) &map->l_mach.fptr_table,
-                       (ElfW(Addr)) NULL, (ElfW(Addr)) fptr_table))
+  if (COMPARE_AND_SWAP (&map->l_mach.fptr_table, NULL, fptr_table))
     map->l_mach.fptr_table_len = len;
   else
     __munmap (fptr_table, len * sizeof (fptr_table[0]));
@@ -249,8 +246,7 @@ _dl_make_fptr (struct link_map *map, const ElfW(Sym) *sym,
       ElfW(Addr) fdesc
        = make_fdesc (ip, map->l_info[DT_PLTGOT]->d_un.d_ptr);
 
-      if (__builtin_expect (COMPARE_AND_SWAP (&ftab[symidx], (ElfW(Addr)) NULL,
-                                             fdesc), 1))
+      if (__builtin_expect (COMPARE_AND_SWAP (&ftab[symidx], 0, fdesc), 1))
        {
          /* No one has updated the entry and the new function
             descriptor has been installed.  */
@@ -276,8 +272,8 @@ _dl_make_fptr (struct link_map *map, const ElfW(Sym) *sym,
 
          do
            f->ip = (ElfW(Addr)) l->free_list;
-         while (! COMPARE_AND_SWAP ((ElfW(Addr) *) &l->free_list,
-                                    f->ip, fdesc));
+         while (! COMPARE_AND_SWAP (&l->free_list, (struct fdesc *) f->ip,
+                                    fdesc));
        }
     }
 
@@ -313,8 +309,8 @@ _dl_unmap (struct link_map *map)
   if (tail)
     do
       tail->ip = (ElfW(Addr)) local.free_list;
-    while (! COMPARE_AND_SWAP ((ElfW(Addr) *) &local.free_list,
-                              tail->ip, (ElfW(Addr)) head));
+    while (! COMPARE_AND_SWAP (&local.free_list, (struct fdesc *) tail->ip,
+                              head));
 
   __munmap (ftab, (map->l_mach.fptr_table_len
                   * sizeof (map->l_mach.fptr_table[0])));