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Rather to my surprise given the amount of testing this code has had,
Kevin Lyles spotted a tree234 bug! copytree234() segfaulted when
asked to copy a tree containing no elements, due to failing to allow
for the case that t->root might be NULL. Fixed, and added a
regression test.

[originally from svn r7092]

--- a/tree234.c

+++ b/tree234.c

@@ -35,6 +35,9 @@

 #ifdef TEST

 #define LOG(x) (printf x)

+#define smalloc malloc

+#define srealloc realloc

+#define sfree free

 #else

 #define LOG(x)

 #endif

@@ -1438,8 +1441,11 @@

     tree234 *t2;

     t2 = newtree234(t->cmp);

-    t2->root = copynode234(t->root, copyfn, copyfnstate);

-    t2->root->parent = NULL;

+    if (t->root) {

+	t2->root = copynode234(t->root, copyfn, copyfnstate);

+	t2->root->parent = NULL;

+    } else

+	t2->root = NULL;

     return t2;

 }

@@ -1885,8 +1891,6 @@

     return strcmp(a, b);

 }

-#define lenof(x) ( sizeof((x)) / sizeof(*(x)) )

-

 char *strings[] = {

     "0", "2", "3", "I", "K", "d", "H", "J", "Q", "N", "n", "q", "j", "i",

     "7", "G", "F", "D", "b", "x", "g", "B", "e", "v", "V", "T", "f", "E",

@@ -2120,11 +2124,12 @@

     tree = newtree234(mycmp);

     cmp = mycmp;

     arraylen = 0;

-    for (i = 0; i < 16; i++) {

-	addtest(strings[i]);

+    for (i = 0; i < 17; i++) {

 	tree2 = copytree234(tree, NULL, NULL);

 	splittest(tree2, array, arraylen);

 	freetree234(tree2);

+	if (i < 16)

+	    addtest(strings[i]);

     }

     freetree234(tree);