Re: stabilize .gcc_except_table with or without -g

[Alexandre Oliva <aoliva at redhat dot com>]

On Nov  5, 2007, Mark Mitchell <mark@codesourcery.com> wrote:

>   /* Comparison function for a splay tree in which the keys are strings.
>      K1 and K2 have the dynamic type "const char *".  Returns <0, 0,
>      or >0 to indicate whether K1 is less than, equal to, or greater
>      than K2, respectively.  */

> probably, we do.  In the body of the function, you could write:

>   /* We use strcmp, rather than just comparing pointers, so that the
>      sort order will not depend on the host system.  */

> If you leave the assertion in, you definitely should comment:

>   /* The strings are always those from IDENTIFIER_NODEs, and, therefore,
>      we should never have two copies of the same string.  */

> The patch is OK with those changes.

Thanks, here's what I'm checking in:

for  gcc/ChangeLog
from  Alexandre Oliva  <aoliva@redhat.com>

	* dwarf2asm.c (splay_tree_compare_strings): New function.
	(dw2_force_const_mem): Use it.

Index: gcc/dwarf2asm.c
===================================================================
--- gcc/dwarf2asm.c.orig	2007-11-25 03:04:19.000000000 -0200
+++ gcc/dwarf2asm.c	2007-11-25 03:31:43.000000000 -0200
@@ -701,6 +701,31 @@ static GTY(()) int dw2_const_labelno;
 # define USE_LINKONCE_INDIRECT 0
 #endif
 
+/* Comparison function for a splay tree in which the keys are strings.
+   K1 and K2 have the dynamic type "const char *".  Returns <0, 0, or
+   >0 to indicate whether K1 is less than, equal to, or greater than
+   K2, respectively.  */
+
+static int
+splay_tree_compare_strings (splay_tree_key k1, splay_tree_key k2)
+{
+  const char *s1 = (const char *)k1;
+  const char *s2 = (const char *)k2;
+  int ret;
+
+  if (s1 == s2)
+    return 0;
+
+  ret = strcmp (s1, s2);
+
+  /* The strings are always those from IDENTIFIER_NODEs, and,
+     therefore, we should never have two copies of the same
+     string.  */
+  gcc_assert (ret);
+
+  return ret;
+}
+
 /* Put X, a SYMBOL_REF, in memory.  Return a SYMBOL_REF to the allocated
    memory.  Differs from force_const_mem in that a single pool is used for
    the entire unit of translation, and the memory is not guaranteed to be
@@ -715,7 +740,9 @@ dw2_force_const_mem (rtx x, bool public)
   tree decl;
 
   if (! indirect_pool)
-    indirect_pool = splay_tree_new_ggc (splay_tree_compare_pointers);
+    /* We use strcmp, rather than just comparing pointers, so that the
+       sort order will not depend on the host system.  */
+    indirect_pool = splay_tree_new_ggc (splay_tree_compare_strings);
 
   gcc_assert (GET_CODE (x) == SYMBOL_REF);
 

-- 
Alexandre Oliva         http://www.lsd.ic.unicamp.br/~oliva/
FSF Latin America Board Member         http://www.fsfla.org/
Red Hat Compiler Engineer   aoliva@{redhat.com, gcc.gnu.org}
Free Software Evangelist  oliva@{lsd.ic.unicamp.br, gnu.org}