SLHAlloc must return NULL when internal allocations fail

The SLHAlloc function keeps using the results of the internal
allocations even when they're NULL which leads to S0C4 ABENDs. This
commit makes SLHAlloc return NULL when the internal allocations fail.

Signed-off-by: Irek Fakhrutdinov <[email protected]>

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## `2.18.1`
 - Bugfix: IARV64 results must be checked for 0x7FFFF000 (#474)
+- Bugfix: SLH should not ABEND when MEMLIMIT is reached (additional NULL check)
 
 ## `2.18.0`
 - Minor `components.zss.logLevels._zss.httpserver=5` debug messages enhancement (#471)

c/utils.c

@@ -1502,6 +1502,7 @@ char *SLHAlloc(ShortLivedHeap *slh, int size){
                       safeMalloc31(size+4,"SLH Oversize Extend"));
     if (bigBlock == NULL){
       reportSLHFailure(slh,size);
+      return NULL;
     }
     int *sizePtr = (int*)bigBlock;
     *sizePtr = size;
@@ -1528,6 +1529,7 @@ char *SLHAlloc(ShortLivedHeap *slh, int size){
                   safeMalloc31(slh->blockSize+4,"SLH Extend") );
     if (data == NULL){
       reportSLHFailure(slh,size);
+      return NULL;
     }
     int *sizePtr = (int*)data;
     *sizePtr = slh->blockSize;