mmap now throws an understandable exception upon trying to mmap a zero length file. fix a bug with calling |dispose on an integer if mmap failed on unix

basis/io/mmap/mmap-tests.factor

@@ -9,3 +9,23 @@ IN: io.mmap.tests
 [ 5 ] [ "mmap-test-file.txt" temp-file [ length ] with-mapped-char-file ] unit-test
 [ "22345" ] [ "mmap-test-file.txt" temp-file ascii file-contents ] unit-test
 [ "mmap-test-file.txt" temp-file delete-file ] ignore-errors
+
+
+[ ]
+[ "mmap-empty-file.txt" temp-file touch-file ] unit-test
+
+! Test for leaking resources bug on Unix
+[ ]
+[
+    100000 [
+        [
+            "mmap-empty-file.txt" temp-file [
+                drop
+            ] with-mapped-file
+        ] [ dup bad-mmap-size? [ drop ] [ rethrow ] if ] recover
+    ] times
+
+    "asdf" "mmap-asdf-file.txt" temp-file [ ascii set-file-contents ] keep [
+        drop
+    ] with-mapped-file
+] unit-test

basis/io/mmap/mmap.factor

@@ -2,15 +2,20 @@
 ! See http://factorcode.org/license.txt for BSD license.
 USING: continuations destructors io.files io.files.info
 io.backend kernel quotations system alien alien.accessors
-accessors system vocabs.loader combinators alien.c-types ;
+accessors system vocabs.loader combinators alien.c-types
+math ;
 IN: io.mmap
 
 TUPLE: mapped-file address handle length disposed ;
 
 HOOK: (mapped-file) os ( path length -- address handle )
 
+ERROR: bad-mmap-size path size ;
+
 : <mapped-file> ( path -- mmap )
-    [ normalize-path ] [ file-info size>> ] bi [ (mapped-file) ] keep
+    [ normalize-path ] [ file-info size>> ] bi
+    dup 0 <= [ bad-mmap-size ] when
+    [ (mapped-file) ] keep
     f mapped-file boa ;
 
 HOOK: close-mapped-file io-backend ( mmap -- )

basis/io/mmap/unix/unix.factor

@@ -9,7 +9,7 @@ IN: io.mmap.unix
 :: mmap-open ( path length prot flags -- alien fd )
     [
         f length prot flags
-        path open-r/w |dispose
+        path open-r/w [ <fd> |dispose drop ] keep
         [ 0 mmap dup MAP_FAILED = [ (io-error) ] when ] keep
     ] with-destructors ;