[perl #46227] [PATCH] Remove passing negative index to array in compilers/imcc/optimizer.c (Coverity CID 20

[via RT]

# New Ticket Created by  Paul Cochrane 
# Please include the string:  [perl #46227]
# in the subject line of all future correspondence about this issue. 
# <URL: http://rt.perl.org/rt3/Ticket/Display.html?id=46227 >

This patch is brought to you by the RT command line utility because
parrotbug doesn't seem to think I'm the 'Hi' virus...

In compilers/imcc/optimizer.c there is the possiblity that a negative
number will be used as an index to an array; see Coverity CID 20.  This
patch removes this issue.  If noone complains, I'll apply the patch in
about 3 days; if it is approved, then I'll apply it at the first
opportunity.

Paul

Index: compilers/imcc/optimizer.c
===================================================================
--- compilers/imcc/optimizer.c  (revision 21951)
+++ compilers/imcc/optimizer.c  (working copy)
@@ -934,11 +934,16 @@
                       (next->type & IF_goto) &&
                       !strcmp(next->op, "branch") &&
                       strcmp(next->r[0]->name, get_branch_reg(ins)->name)) {
+                    const int regno = get_branch_regno(ins);
                     IMCC_debug(interp, DEBUG_OPT1,
                             "found branch to branch '%s' %I\n",
                             r->first_ins->r[0]->name, next);
                     unit->ostat.branch_branch++;
-                    ins->r[get_branch_regno(ins)] = next->r[0];
+                    if (regno < 0) {
+                        real_exception(interp, NULL, 1,
+                                "Register number determination failed in 
branch_branch()");
+                    }
+                    ins->r[regno] = next->r[0];
                     changed = 1;
                 }
             }