Based on a recent discussion with George, fix bug 977 to prevent

reading from outside the allocated area.  This bug was *probably*
harmless, but valgrind correctly identified a read from outside the
alloca'ed area (although that value was subsequently never used).
It's safer to just never read it in the first place.

Added "JMS" comments in the code where I made changes.  Following up
with a mail to George...

This commit was SVN r2901.

src/datatype/dt_optimize.c

@@ -64,7 +64,7 @@ int ompi_ddt_optimize_short( dt_desc_t* pData, int count,
    pStack->disp = 0;
    pos_desc  = 0;
    
-  next_loop:
+   /* JMS: removed next_loop here */
    totalDisp = pStack->disp;
    while( stack_pos >= 0 ) {
       if( pData->desc.desc[pos_desc].type == DT_END_LOOP ) { /* end of the current loop */
@@ -81,9 +81,14 @@ int ompi_ddt_optimize_short( dt_desc_t* pData, int count,
                     pData->desc.desc[pos_desc].extent );
          stack_pos--;
          pStack--;
-         if( stack_pos >= 0 ) pStartLoop->disp = (pElemDesc - 1)->count;
+         /* JMS: made this into a block and added the totalDisp= line */
+         if( stack_pos >= 0 ) {
+             pStartLoop->disp = (pElemDesc - 1)->count;
+             totalDisp = pStack->disp;
+         }
          pos_desc++;
-         goto next_loop;
+         /* JMS: changed this from "goto next_loop" to "continue" */
+         continue;
       }
       if( pData->desc.desc[pos_desc].type == DT_LOOP ) {
          dt_elem_desc_t* pEndLoop = &(pData->desc.desc[pos_desc + pData->desc.desc[pos_desc].disp]);
@@ -134,7 +139,12 @@ int ompi_ddt_optimize_short( dt_desc_t* pData, int count,
             pos_desc++;
             DUMP_STACK( pStack, stack_pos, pData->desc, "advance loops" );
          }
-         goto next_loop;
+         /* JMS: added block */
+         if( stack_pos >= 0 ) {
+             totalDisp = pStack->disp;
+         }
+         /* JMS: changed "goto next_loop" to "continue" */
+         continue;
       }
       /* now here we have a basic datatype */
       type = pData->desc.desc[pos_desc].type;