dereference-pointer: check for null pointer.

* libguile/foreign.c (scm_dereference_pointer): Check for attempts to
  dereference a null pointer.

* test-suite/tests/foreign.test ("null pointer"): Add test.

2 files changed, 11 insertions, 1 deletions

diff --git a/libguile/foreign.c b/libguile/foreign.c
index 90a4fcab4..01af90019 100644
--- a/libguile/foreign.c
+++ b/libguile/foreign.c
@@ -342,9 +342,15 @@ SCM_DEFINE (scm_dereference_pointer, "dereference-pointer", 1, 0, 0,
 	    "holds a pointer, return this pointer.")
 #define FUNC_NAME s_scm_dereference_pointer
 {
+  void **ptr;
+
   SCM_VALIDATE_POINTER (1, pointer);
 
-  return scm_from_pointer (* (void **) SCM_POINTER_VALUE (pointer), NULL);
+  ptr = SCM_POINTER_VALUE (pointer);
+  if (SCM_UNLIKELY (ptr == NULL))
+    null_pointer_error (FUNC_NAME);
+
+  return scm_from_pointer (*ptr, NULL);
 }
 #undef FUNC_NAME
 
diff --git a/test-suite/tests/foreign.test b/test-suite/tests/foreign.test
index 4b129db24..acdb3db05 100644
--- a/test-suite/tests/foreign.test
+++ b/test-suite/tests/foreign.test
@@ -51,6 +51,10 @@
   (pass-if "null-pointer? %null-pointer"
     (null-pointer? %null-pointer))
 
+  (pass-if-exception "dereference-pointer %null-pointer"
+    exception:null-pointer-error
+    (dereference-pointer %null-pointer))
+
   (pass-if-exception "pointer->bytevector %null-pointer"
     exception:null-pointer-error
     (pointer->bytevector %null-pointer 7)))