From 650be6adc0c60647a3f5bed07e52584b64ee3e2c Mon Sep 17 00:00:00 2001
From: Kris Katterjohn <katterjohn@gmail.com>
Date: Fri, 4 Oct 2019 20:38:15 -0500
Subject: [PATCH] mmapped heaps: correctly check for mmap failure

When mmap fails it returns MAP_FAILED, not NULL.  POSIX does not
define the value for MAP_FAILED, but on at least the BSDs and Linux
its value is ((void *) -1).
---
 gc.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/gc.c b/gc.c
index e9e3aa87..8802fbdf 100644
--- a/gc.c
+++ b/gc.c
@@ -502,10 +502,11 @@ sexp_heap sexp_make_heap (size_t size, size_t max_size, size_t chunk_size) {
 #if SEXP_USE_MMAP_GC
   h =  mmap(NULL, sexp_heap_pad_size(size), PROT_READ|PROT_WRITE|PROT_EXEC,
             MAP_ANON|MAP_PRIVATE, 0, 0);
+  if (h == MAP_FAILED) return NULL;
 #else
   h =  sexp_malloc(sexp_heap_pad_size(size));
-#endif
   if (! h) return NULL;
+#endif
   h->size = size;
   h->max_size = max_size;
   h->chunk_size = chunk_size;