Add posix_mkfifo Erlang spec and export

The NIF existed but was not exported from atomvm.erl.
Also tighten mode validation to reject negative values.

Signed-off-by: Davide Bettio <davide@uninstall.it>

Author: bettio

libs/eavmlib/src/atomvm.erl

@@ -45,6 +45,7 @@
     posix_pwrite/3,
     posix_fsync/1,
     posix_ftruncate/2,
+    posix_mkfifo/2,
     posix_mkdir/2,
     posix_rmdir/1,
     posix_rename/2,
@@ -375,6 +376,18 @@ posix_fsync(_File) ->
 posix_ftruncate(_File, _Length) ->
     erlang:nif_error(undefined).
 
+%%-----------------------------------------------------------------------------
+%% @param   Path    Path to the new FIFO special file
+%% @param   Mode    Permission bits for the new FIFO
+%% @returns `ok' or an error tuple
+%% @doc     Create a FIFO special file (named pipe) using `mkfifo(2)'.
+%% @end
+%%-----------------------------------------------------------------------------
+-spec posix_mkfifo(Path :: iodata(), Mode :: non_neg_integer()) ->
+    ok | {error, posix_error()}.
+posix_mkfifo(_Path, _Mode) ->
+    erlang:nif_error(undefined).
+
 %%-----------------------------------------------------------------------------
 %% @param   Path    Path to the directory to create
 %% @param   Mode    Permission bits for the new directory

src/libAtomVM/posix_nifs.c

@@ -954,7 +954,7 @@ static term nif_atomvm_posix_mkfifo(Context *ctx, int argc, term argv[])
     UNUSED(argc);
     term path_term = argv[0];
     term mode_term = argv[1];
-    VALIDATE_VALUE(mode_term, term_is_integer);
+    VALIDATE_VALUE(mode_term, term_is_non_neg_int);
 
     int ok;
     const char *path = interop_term_to_string(path_term, &ok);