From 0296e40fc73d88b33e78899f95ef7b6c1a957d06 Mon Sep 17 00:00:00 2001
From: Paul Smith <psmith@gnu.org>
Date: Sun, 22 Sep 2013 12:13:28 -0400
Subject: [PATCH] Allow loaded objects to opt out of the "auto-rebuild"
 feature.

---
 ChangeLog     |  4 ++++
 doc/make.texi |  7 +++++--
 read.c        | 14 +++++++++++---
 3 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 8c5b3e5d..5b0fcb59 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,9 @@
 2013-09-22  Paul Smith  <psmith@gnu.org>
 
+	* read.c (eval): If load_file() returns -1, don't add this to the
+	"to be rebuilt" list.
+	* doc/make.texi (load Directive): Document it.
+
 	* guile.c (guile_gmake_setup): Don't initialize Guile so early.
 	(func_guile): Lazily initialize Guile the first time the $(guile ..)
 	function is invoked.  Guile can steal file descriptors which
diff --git a/doc/make.texi b/doc/make.texi
index 62c71910..f89f8b77 100644
--- a/doc/make.texi
+++ b/doc/make.texi
@@ -10910,7 +10910,8 @@ The @code{load} directive and extension capability is considered a
 ``technology preview'' in this release of GNU make.  We encourage you
 to experiment with this feature and we appreciate any feedback on it.
 However we cannot guarantee to maintain backward-compatibility in the
-next release.
+next release.  Consider using GNU Guile instead for extending GNU make
+(@pxref{Guile Function, ,The @code{guile} Function}).
 @end quotation
 @end cartouche
 
@@ -10978,7 +10979,9 @@ same directive.
 The initializing function will be provided the file name and line
 number of the invocation of the @code{load} operation.  It should
 return a value of type @code{int}, which must be @code{0} on failure
-and non-@code{0} on success.
+and non-@code{0} on success.  If the return value is @code{-1}, then
+GNU make will @emph{not} attempt to rebuild the object file
+(@pxref{Remaking Loaded Objects, ,How Loaded Objects Are Remade}).
 
 For example:
 
diff --git a/read.c b/read.c
index a4ca72d6..7f90b9b9 100644
--- a/read.c
+++ b/read.c
@@ -947,19 +947,27 @@ eval (struct ebuffer *ebuf, int set_default)
                                   PARSEFS_NOAR);
           free (p);
 
-          /* Load each file and add it to the list "to be rebuilt".  */
+          /* Load each file.  */
           while (files != 0)
             {
               struct nameseq *next = files->next;
               const char *name = files->name;
               struct dep *deps;
+              int r;
+
+              /* Load the file.  0 means failure.  */
+              r = load_file (&ebuf->floc, &name, noerror);
+              if (! r && ! noerror)
+                fatal (&ebuf->floc, _("%s: failed to load"), name);
 
               free_ns (files);
               files = next;
 
-              if (! load_file (&ebuf->floc, &name, noerror) && ! noerror)
-                fatal (&ebuf->floc, _("%s: failed to load"), name);
+              /* Return of -1 means a special load: don't rebuild it.  */
+              if (r == -1)
+                continue;
 
+              /* It succeeded, so add it to the list "to be rebuilt".  */
               deps = alloc_dep ();
               deps->next = read_files;
               read_files = deps;