[SV 62706] Only second-expand targets that might be built

Second-expand only the prerequisites of the targets being built.
Defer second-expanding the prerequisites of targets until we need
to decide if they should be built.

* NEWS: Mention the change in behavior.
* doc/make.texi (Secondary Expansion): Document the new behavior.
* src/filedef.h (struct file): Add flag snapped.
(expand_deps): Declare a function to second expand the
prerequisites of a target.
* src/file.c (rehash_file): Merge flag snapped.
(expand_deps): Remove qualifier static. Check flag snapped.
(snap_deps): Remove the loop which performed second expansion for all
targets.
* src/remake.c (update_file_1): Second expand the prerequisites of
the considered target.
* tests/scripts/features/se_explicit: Add tests.
* tests/scripts/features/se_implicit: Ditto.
* tests/scripts/features/se_statpat: Ditto.

1 files changed, 3 insertions, 0 deletions

diff --git a/src/filedef.h b/src/filedef.h
index 4330d787..1eb8f61c 100644
--- a/src/filedef.h
+++ b/src/filedef.h
@@ -110,6 +110,8 @@ struct file
                                    diagnostics has been issued (dontcare). */
     unsigned int was_shuffled:1; /* Did we already shuffle 'deps'? used when
                                     --shuffle passes through the graph.  */
+    unsigned int snapped:1;     /* True if the deps of this file have been
+                                   secondary expanded.  */
   };
 
 
@@ -120,6 +122,7 @@ struct file *lookup_file (const char *name);
 struct file *enter_file (const char *name);
 struct dep *split_prereqs (char *prereqstr);
 struct dep *enter_prereqs (struct dep *prereqs, const char *stem);
+void expand_deps (struct file *f);
 struct dep *expand_extra_prereqs (const struct variable *extra);
 void remove_intermediates (int sig);
 void snap_deps (void);