[Libguestfs] [PATCH libnbd v3 2/6] generator: Add attribute((nonnull)) annotations to non-NULL parameters

[Richard W.M. Jones]

For API parameters that are pointers and must not be NULL, add the
appropriate GCC annotations.

Reviewed-by: Laszlo Ersek <lersek at redhat.com>
---
 generator/C.ml              | 59 +++++++++++++++++++++++++++++++++++--
 tests/errors-connect-null.c |  4 +++
 2 files changed, 61 insertions(+), 2 deletions(-)

diff --git a/generator/C.ml b/generator/C.ml
index 66498a7d88..6e4538fd34 100644
--- a/generator/C.ml
+++ b/generator/C.ml
@@ -107,6 +107,28 @@ let
   | UInt64 n -> [n]
   | UIntPtr n -> [n]
 
+(* Map function arguments to __attribute__((nonnull)) annotations.
+ * Because a single arg may map to multiple C parameters this
+ * returns a list.  Note: true => add attribute nonnull.
+ *)
+let arg_attr_nonnull =
+  function
+  (* BytesIn/Out are passed using a non-null pointer, and size_t *)
+  | BytesIn _ | BytesOut _
+  | BytesPersistIn _ | BytesPersistOut _ -> [ true; false ]
+  (* sockaddr is also non-null pointer, and length *)
+  | SockAddrAndLen (n, len) -> [ true; false ]
+  (* strings should be marked as non-null *)
+  | Path _ | String _ -> [ true ]
+  (* list of strings should be marked as non-null *)
+  | StringList n -> [ true ]
+  (* numeric and other non-pointer types are not able to be null *)
+  | Bool _ | Closure _ | Enum _ | Fd _ | Flags _
+  | Int _ | Int64 _ | SizeT _
+  | UInt _ | UInt32 _ | UInt64 _ | UIntPtr _ -> [ false ]
+
+let optarg_attr_nonnull (OClosure _ | OFlags _) = [ false ]
+
 let rec print_arg_list ?(wrap = false) ?maxcol ?handle ?types ?(parens = true)
           ?closure_style args optargs =
   if parens then pr "(";
@@ -216,7 +238,21 @@ let
 let print_fndecl ?wrap ?closure_style name args optargs ret =
   pr "extern ";
   print_call ?wrap ?closure_style name args optargs ret;
-  pr ";\n"
+
+  (* Output __attribute__((nonnull)) for the function parameters:
+   * eg. struct nbd_handle *, int, char *
+   *     => [ true, false, true ]
+   *     => LIBNBD_ATTRIBUTE_NONNULL((1,3))
+   *     => __attribute__((nonnull,(1,3)))
+   *)
+  let nns : bool list =
+    [ true ] (* struct nbd_handle * *)
+    @ List.flatten (List.map arg_attr_nonnull args)
+    @ List.flatten (List.map optarg_attr_nonnull optargs) in
+  let nns = List.mapi (fun i b -> (i+1, b)) nns in
+  let nns = filter_map (fun (i, b) -> if b then Some i else None) nns in
+  let nns : string list = List.map string_of_int nns in
+  pr "\n    LIBNBD_ATTRIBUTE_NONNULL((%s));\n" (String.concat "," nns)
 
 let rec print_cbarg_list ?(wrap = false) ?maxcol ?types ?(parens = true)
           cbargs =
@@ -349,6 +385,19 @@ let
   pr "extern \"C\" {\n";
   pr "#endif\n";
   pr "\n";
+  pr "#if defined(__GNUC__)\n";
+  pr "#define LIBNBD_GCC_VERSION \\\n";
+  pr "    (__GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__)\n";
+  pr "#endif\n";
+  pr "\n";
+  pr "#ifndef LIBNBD_ATTRIBUTE_NONNULL\n";
+  pr "#if defined(__GNUC__) && LIBNBD_GCC_VERSION >= 120000 /* gcc >= 12.0 */\n";
+  pr "#define LIBNBD_ATTRIBUTE_NONNULL(s) __attribute__((__nonnull__ s))\n";
+  pr "#else\n";
+  pr "#define LIBNBD_ATTRIBUTE_NONNULL(s)\n";
+  pr "#endif\n";
+  pr "#endif /* ! defined LIBNBD_ATTRIBUTE_NONNULL */\n";
+  pr "\n";
   pr "struct nbd_handle;\n";
   pr "\n";
   List.iter (
@@ -382,7 +431,7 @@ let
   pr "extern struct nbd_handle *nbd_create (void);\n";
   pr "#define LIBNBD_HAVE_NBD_CREATE 1\n";
   pr "\n";
-  pr "extern void nbd_close (struct nbd_handle *h);\n";
+  pr "extern void nbd_close (struct nbd_handle *h); /* h can be NULL */\n";
   pr "#define LIBNBD_HAVE_NBD_CLOSE 1\n";
   pr "\n";
   pr "extern const char *nbd_get_error (void);\n";
@@ -770,6 +819,12 @@ let
   pr "\n";
   pr "#include <pthread.h>\n";
   pr "\n";
+  pr "/* GCC will remove NULL checks from this file for any parameter\n";
+  pr " * annotated with attribute((nonnull)).  See RHBZ#1041336.  To\n";
+  pr " * avoid this, disable the attribute when including libnbd.h.\n";
+  pr " */\n";
+  pr "#define LIBNBD_ATTRIBUTE_NONNULL(s)\n";
+  pr "\n";
   pr "#include \"libnbd.h\"\n";
   pr "#include \"internal.h\"\n";
   pr "\n";
diff --git a/tests/errors-connect-null.c b/tests/errors-connect-null.c
index 27b21f0f8f..b975181afb 100644
--- a/tests/errors-connect-null.c
+++ b/tests/errors-connect-null.c
@@ -27,6 +27,10 @@
 #include <string.h>
 #include <errno.h>
 
+/* GCC will warn that we are passing NULL (or worse), so to do this
+ * test we must remove the header file attribute.
+ */
+#define LIBNBD_ATTRIBUTE_NONNULL(s)
 #include <libnbd.h>
 
 static char *progname;
-- 
2.37.0.rc2