[Bug target/47997] gcc on macosx: "ld: warning: -fwritable-strings not compatible with literal CF/NSString"

[iains at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47997

--- Comment #23 from Iain Sandoe <iains at gcc dot gnu.org> 2011-07-21 14:52:26 UTC ---
OK, done some more debugging ....

so one can't call fix_string_type () twice on the same string and get a
sensible result...
... the determination of the string type by equating to one of the global_tree
nodes is broken on the second call since the first call overwrites the tree
type:

code fragment from fix_string_type ():

  i_type = build_index_type (size_int (nchars - 1));
  a_type = build_array_type (e_type, i_type);
  if (c_dialect_cxx() || warn_write_strings)
    a_type = c_build_qualified_type (a_type, TYPE_QUAL_CONST);

  TREE_TYPE (value) = a_type;

===

So either this is wrong - or we need some way to know that fix_string_type has
already been called (by lex_string()).

in the meantime - this just avoids making the second call, because I can't see
that there's any case in which objc_build_string_object () is called without a
string from lex_string ()?  
(grep suggests not).

thus; assuming that fix_string_type () is behaving as expected, the following
is a fix :

Index: gcc/objc/objc-act.c
===================================================================
--- gcc/objc/objc-act.c (revision 176554)
+++ gcc/objc/objc-act.c (working copy)
@@ -3132,9 +3132,8 @@ objc_build_string_object (tree string)
   struct string_descriptor *desc, key;
   void **loc;

-  /* Prep the string argument.  */
-  string = fix_string_type (string);
-  TREE_SET_CODE (string, STRING_CST);
+  gcc_checking_assert (TREE_CODE (string) == STRING_CST);
+
   length = TREE_STRING_LENGTH (string) - 1;

   /* The target may have different ideas on how to construct an ObjC string