Merge branch 'maint-0.2.4' into maint-0.2.5

1 files changed, 30 insertions, 19 deletions

diff --git a/src/or/routerparse.c b/src/or/routerparse.c
index 5b70142a43..524a575480 100644
--- a/src/or/routerparse.c
+++ b/src/or/routerparse.c
@@ -4301,26 +4301,37 @@ tor_version_compare(tor_version_t *a, tor_version_t *b)
   int i;
   tor_assert(a);
   tor_assert(b);
-  if ((i = a->major - b->major))
-    return i;
-  else if ((i = a->minor - b->minor))
-    return i;
-  else if ((i = a->micro - b->micro))
-    return i;
-  else if ((i = a->status - b->status))
-    return i;
-  else if ((i = a->patchlevel - b->patchlevel))
-    return i;
-  else if ((i = strcmp(a->status_tag, b->status_tag)))
-    return i;
-  else if ((i = a->svn_revision - b->svn_revision))
-    return i;
-  else if ((i = a->git_tag_len - b->git_tag_len))
-    return i;
-  else if (a->git_tag_len)
-    return fast_memcmp(a->git_tag, b->git_tag, a->git_tag_len);
+
+  /* We take this approach to comparison to ensure the same (bogus!) behavior
+   * on all inputs as we would have seen before bug #21278 was fixed. The
+   * only important difference here is that this method doesn't cause
+   * a signed integer underflow.
+   */
+#define CMP(field) do {                               \
+    unsigned aval = (unsigned) a->field;              \
+    unsigned bval = (unsigned) b->field;              \
+    int result = (int) (aval - bval);                 \
+    if (result < 0)                                   \
+      return -1;                                      \
+    else if (result > 0)                              \
+      return 1;                                       \
+  } while (0)
+
+  CMP(major);
+  CMP(minor);
+  CMP(micro);
+  CMP(status);
+  CMP(patchlevel);
+  if ((i = strcmp(a->status_tag, b->status_tag)))
+     return i;
+  CMP(svn_revision);
+  CMP(git_tag_len);
+  if (a->git_tag_len)
+     return fast_memcmp(a->git_tag, b->git_tag, a->git_tag_len);
   else
-    return 0;
+     return 0;
+
+#undef CMP
 }
 
 /** Return true iff versions <b>a</b> and <b>b</b> belong to the same series.