From: Ivan Maidanski <ivmai@mail.ru>
Date: Tue, 25 Oct 2016 21:56:02 +0000 (+0300)
Subject: Eliminate 'dereference of null' CSA false warning in array_mark_proc
X-Git-Tag: v7.6.2~391
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=f842995de788fba6bf366a057393ce4c0e6550c3;p=gc

Eliminate 'dereference of null' CSA false warning in array_mark_proc

The exact warning message is: Access to field 'mse_start' results in a
dereference of a null pointer (loaded from variable 'new_mark_stack_ptr').

Note: the warning is eliminated regardless of assertion checking status.

* typd_mlc.c (GC_array_mark_proc): Call ABORT if mark_stack_ptr is NULL
(thus orig_mark_stack_ptr is ensured to be non-NULL after the check).
---

diff --git a/typd_mlc.c b/typd_mlc.c
index b7688b06..3e063736 100644
--- a/typd_mlc.c
+++ b/typd_mlc.c
@@ -495,6 +495,9 @@ STATIC mse * GC_array_mark_proc(word * addr, mse * mark_stack_ptr,
                                                     mark_stack_ptr,
                                                     mark_stack_limit-1);
     if (new_mark_stack_ptr == 0) {
+        /* Explicitly instruct Clang Static Analyzer that ptr is non-null. */
+        if (NULL == mark_stack_ptr) ABORT("Bad mark_stack_ptr");
+
         /* Doesn't fit.  Conservatively push the whole array as a unit  */
         /* and request a mark stack expansion.                          */
         /* This cannot cause a mark stack overflow, since it replaces   */