New function: compile-update-file.

The new function only compiles a file if the output file doesn't exist
or is out of date.

In addition, both compile-file now deletes the output file if
compilation fails, and has a documented return value.

* lisplib.c (compiler_set_entries): Add autoload entry fro
compile-update-file.
(open-compile-streams): Accepts a third argument: a function to test the
input stream against the output path. The output file is opened, and the
streams are returned, only if that test function returns true.
Also, a third element is returned: the output path. This lets the
caller to know what to delete, if the output file must be deleted.
(compile-file-conditionally): New internal function, formed from
compile-file. Takes an extra argument, the test function to pass to
open-compile-streams. Compilation is skipped if open-compile-streams
returns nil. Internals reshuffled a bit. If compilation doesn't set the
success flag, then the with-resources logic now removes the output file
in addition to closing the output stream. Prior to setting the success
flag, we flush the output stream.

* txr.1: Documented new function, all return values, and deletion of
output file on unsuccessful compilation.

1 files changed, 2 insertions, 1 deletions

diff --git a/lisplib.c b/lisplib.c
index 78d6c024..d143ab2d 100644
--- a/lisplib.c
+++ b/lisplib.c
@@ -716,7 +716,8 @@ static val compiler_set_entries(val dlt, val fun)
     nil
   };
   val name[] = {
-    lit("compile-toplevel"), lit("compile-file"), lit("compile"),
+    lit("compile-toplevel"), lit("compile"), lit("compile-file"),
+    lit("compile-update-file"),
     lit("with-compilation-unit"), lit("dump-compiled-objects"),
     nil
   };