[Findutils-patches] [PATCH] Compare function pointers with memcmp(); fixes Savannah bug #20263.

[James Youngman]

2007-06-26  James Youngman  <address@hidden>

        Compare function pointers with memcmp(); fixes Savannah bug #20263.
        * find/tree.c (cost_table_comparison): Use memcmp() to compare
        function pointers, since ISO C does not specify that it will be
        possible to do magnitude comparisons on them, and casting them to
        void* is non-portable.
---
 ChangeLog   |    7 +++++++
 find/tree.c |   29 +++++++++++++++--------------
 2 files changed, 22 insertions(+), 14 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 0c0d6fa..5115006 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2007-06-26  James Youngman  <address@hidden>
+
+       * find/tree.c (cost_table_comparison): Use memcmp() to compare
+       function pointers, since ISO C does not specify that it will be
+       possible to do magnitude comparisons on them, and casting them to
+       void* is non-portable.
+
 2007-06-26  Eric Blake  <address@hidden>
 
        * import-gnulib.config (modules): Allow ./configure
diff --git a/find/tree.c b/find/tree.c
index 66414fe..02eac11 100644
--- a/find/tree.c
+++ b/find/tree.c
@@ -980,21 +980,20 @@ check_sorted(void *base, size_t members, size_t 
membersize,
 static int
 cost_table_comparison(const void *p1, const void *p2)
 {
+  /* We have to compare the function pointers with memcmp(), 
+   * because ISO C does not allow magnitude comparison of 
+   * function pointers (just equality testing).
+   */
   const struct pred_cost_lookup *pc1 = p1;
   const struct pred_cost_lookup *pc2 = p2;
-  const void* pf1 = (const void*)pc1->fn;
-  const void* pf2 = (const void*)pc2->fn;
-
-  /* We use casts to void* for > comparison because not all C
-   * compilers allow order comparison between functions.  For example,
-   * that would fail on DEC Alpha OSF/1 with native cc.
-   */
-  if (pc1->fn == pc2->fn)
-    return 0;
-  else if (pf1 > pf2)
-    return 1;
-  else
-    return -1;
+  union {
+    PRED_FUNC pfn;
+    char mem[sizeof (PRED_FUNC)];
+  } u1, u2;
+
+  u1.pfn = pc1->fn;
+  u2.pfn = pc2->fn;
+  return memcmp(u1.mem, u2.mem, sizeof(u1.pfn));
 }
 
 static enum EvaluationCost
@@ -1035,6 +1034,8 @@ get_pred_cost(const struct predicate *p)
 
       if (!pred_table_sorted)
        {
+         size_t i;
+         
          qsort(costlookup,
                sizeof(costlookup)/sizeof(costlookup[0]),
                sizeof(costlookup[0]),
@@ -1045,7 +1046,7 @@ get_pred_cost(const struct predicate *p)
                            sizeof(costlookup[0]),
                            cost_table_comparison))
            {
-             error(1, 0, "Failed to sort the costlookup array.");
+             error(1, 0, "Failed to sort the costlookup array (indirect).");
            }
          pred_table_sorted = 1;
        }
-- 
1.5.2.1