Ensure error_string() never returns NULL

A Coverity check indicated that ther are platforms where strerror() will
return NULL for unknown, e.g. negative error numbers. Chances are that
these platforms will have problems with NULL arguments to printf() too.

1 files changed, 12 insertions, 1 deletions

diff --git a/dhash/examples/dhash_test.c b/dhash/examples/dhash_test.c
index 8c11227..7b4cbbf 100644
--- a/dhash/examples/dhash_test.c
+++ b/dhash/examples/dhash_test.c
@@ -35,10 +35,21 @@ int verbose = 0;
 
 const char *error_string(int error)
 {
+    const char *str;
+
     if (IS_HASH_ERROR(error))
         return hash_error_string(error);
 
-    return strerror(error);
+    if (error < 0) {
+        return "Negative error codes are not supported.";
+    }
+
+    str = strerror(error);
+    if (str == NULL) {
+        return "strerror() returned NULL.";
+    }
+
+    return str;
 }
 
 char *key_string(hash_key_t *key)