Support the .EXTRA_PREREQS special variable

Initial implementation by Christof Warlich <cwarlich@gmx.de>

* NEWS: Announce the new feature.
* doc/make.texi (Other Special Variables): Document .EXTRA_PREREQS.
* src/dep.h (struct dep): New flag to note extra prereq deps.
* src/filedef.h (expand_extra_prereqs): Declare a function to expand
the value of .EXTRA_PREREQS.
* src/file.c (expand_extra_prereqs): Given a struct variable lookup
of .EXTRA_PREREQS, convert it into a list of deps and for each one
make sure it has a struct file and has the new flag set.
(snap_file): A new function invoked by hash_map that will perform
per-file operations: set up second expansion, intermediate, and also
.EXTRA_PREREQS.  Manage circular dependencies by ignoring them.
(snap_deps): Defer per-file operations until the end.  Look up the
global .EXTRA_PREREQS and pass it along to snap_file for each file.
* src/implicit.c (struct patdeps): Remember the extra prereqs flag.
(pattern_search): Transfer extra prereqs flag settings into the
matched pattern rule.
* src/rule.h (snap_implicit_rules): Rename count_implicit_rules to
snap_implicit_rules since we now do more than count.
* src/rule.c (snap_implicit_rules): As we walk through all the pattern
rules, add in any global .EXTRA_PREREQS to the dep list.  Ensure we
take them into account for the max number of prereqs and name length.
* src/main.c (main): Add extra-prereqs to .FEATURES.
Call the renamed snap_implicit_rules.
* tests/scripts/variables/EXTRA_PREREQS: Add tests.

AUTHORS

@@ -68,6 +68,7 @@ Other contributors:
   David Boyce <dsb@boyski.com>
   Frank Heckenbach <f.heckenbach@fh-soft.de>
   Kaz Kylheku <kaz@kylheku.com>
+  Christof Warlich <cwarlich@gmx.de>
 
 With suggestions/comments/bug reports from a cast of ... well ...
 hundreds, anyway :)

NEWS

@@ -48,6 +48,13 @@ http://sv.gnu.org/bugs/index.php?group=make&report_id=111&fix_release_id=108&set
   search for 'grouped-target' in the .FEATURES special variable.
   Implementation contributed by Kaz Kylheku <kaz@kylheku.com>
 
+* New feature: .EXTRA_PREREQS variable
+  Words in this variable are considered prerequisites of targets but they are
+  not added to any of the automatic variable values when expanding the
+  recipe.  This variable can either be global (applies to all targets) or
+  a target-specific variable.  To detect this feature search for 'extra-prereqs'
+  in the .FEATURES special variable.
+
 * Makefiles can now specify the '-j' option in their MAKEFLAGS variable and
   this will cause make to enable that parallelism mode.
 

doc/make.texi

@@ -6631,6 +6631,57 @@ Supports dynamically loadable objects for creating custom extensions.
 Expands to a list of directories that @code{make} searches for
 included makefiles (@pxref{Include, , Including Other Makefiles}).
 
+@vindex .EXTRA_PREREQS @r{(prerequisites not added to automatic variables)}
+@item .EXTRA_PREREQS
+Each word in this variable is a new prerequisite which is added to
+targets for which it is set.  These prerequisites differ from normal
+prerequisites in that they do not appear in any of the automatic
+variables (@pxref{Automatic Variables}).  This allows prerequisites to
+be defined which do not impact the recipe.
+
+Consider a rule to link a program:
+
+@example
+myprog: myprog.o file1.o file2.o
+       $(CC) $(CFLAGS) $(LDFLAGS) -o $@@ $^ $(LDLIBS)
+@end example
+
+Now suppose you want to enhance this makefile to ensure that updates
+to the compiler cause the program to be re-linked.  You can add the
+compiler as a prerequisite, but you must ensure that it's not passed
+as an argument to link command.  You'll need something like this:
+
+@example
+myprog: myprog.o file1.o file2.o $(CC)
+       $(CC) $(CFLAGS) $(LDFLAGS) -o $@@ $(filter-out $(CC),$^) $(LDLIBS)
+@end example
+
+Then consider having multiple extra prerequisites: they would all have
+to be filtered out.  Using @code{.EXTRA_PREREQS} and target-specific
+variables provides a simpler solution:
+
+@example
+myprog: myprog.o file1.o file2.o
+       $(CC) $(CFLAGS) $(LDFLAGS) -o $@@ $^ $(LDLIBS)
+myprog: .EXTRA_PREREQS = $(CC)
+@end example
+
+This feature can also be useful if you want to add prerequisites to a
+makefile you cannot easily modify: you can create a new file such as
+@file{extra.mk}:
+
+@example
+myprog: .EXTRA_PREREQS = $(CC)
+@end example
+
+then invoke @code{make -f extra.mk -f Makefile}.
+
+Setting @code{.EXTRA_PREREQS} globally will cause those prerequisites
+to be added to all targets (which did not themselves override it with
+a target-specific value).  Note @code{make} is smart enough not to add
+a prerequisite listed in @code{.EXTRA_PREREQS} as a prerequisite to
+itself.
+
 @end table
 
 @node Conditionals, Functions, Using Variables, Top

src/commands.c

@@ -133,7 +133,7 @@ set_file_variables (struct file *file)
   /* $< is the first not order-only dependency.  */
   less = "";
   for (d = file->deps; d != 0; d = d->next)
-    if (!d->ignore_mtime)
+    if (!d->ignore_mtime && !d->ignore_automatic_vars)
       {
         if (!d->need_2nd_expansion)
           less = dep_name (d);
@@ -178,7 +178,7 @@ set_file_variables (struct file *file)
     bar_len = 0;
     for (d = file->deps; d != 0; d = d->next)
       {
-        if (!d->need_2nd_expansion)
+        if (!d->need_2nd_expansion && !d->ignore_automatic_vars)
           {
             if (d->ignore_mtime)
               bar_len += strlen (dep_name (d)) + 1;
@@ -200,7 +200,7 @@ set_file_variables (struct file *file)
 
     qmark_len = plus_len + 1;   /* Will be this or less.  */
     for (d = file->deps; d != 0; d = d->next)
-      if (! d->ignore_mtime && ! d->need_2nd_expansion)
+      if (! d->ignore_mtime && ! d->need_2nd_expansion && ! d->ignore_automatic_vars)
         {
           const char *c = dep_name (d);
 
@@ -247,7 +247,7 @@ set_file_variables (struct file *file)
 
     for (d = file->deps; d != 0; d = d->next)
       {
-        if (d->need_2nd_expansion)
+        if (d->need_2nd_expansion || d->ignore_automatic_vars)
           continue;
 
         slot = hash_find_slot (&dep_hash, d);
@@ -269,7 +269,7 @@ set_file_variables (struct file *file)
       {
         const char *c;
 
-        if (d->need_2nd_expansion || hash_find_item (&dep_hash, d) != d)
+        if (d->need_2nd_expansion || d->ignore_automatic_vars || hash_find_item (&dep_hash, d) != d)
           continue;
 
         c = dep_name (d);

src/dep.h

@@ -48,7 +48,8 @@ struct nameseq
     unsigned int changed : 1;                   \
     unsigned int ignore_mtime : 1;              \
     unsigned int staticpattern : 1;             \
-    unsigned int need_2nd_expansion : 1
+    unsigned int need_2nd_expansion : 1;        \
+    unsigned int ignore_automatic_vars : 1
 
 struct dep
   {

src/file.c

@@ -550,15 +550,6 @@ enter_prereqs (struct dep *deps, const char *stem)
   return deps;
 }
 
-/* Set the intermediate flag.  */
-
-static void
-set_intermediate (const void *item)
-{
-  struct file *f = (struct file *) item;
-  f->intermediate = 1;
-}
-
 /* Expand and parse each dependency line. */
 static void
 expand_deps (struct file *f)
@@ -644,13 +635,69 @@ expand_deps (struct file *f)
     }
 }
 
-/* Reset the updating flag.  */
+/* Add extra prereqs to the file in question.  */
+
+struct dep *
+expand_extra_prereqs (const struct variable *extra)
+{
+  struct dep *prereqs = extra ? split_prereqs (variable_expand (extra->value)) : NULL;
+
+  for (struct dep *d = prereqs; d; d = d->next)
+    {
+      d->file = lookup_file (d->name);
+      if (!d->file)
+        d->file = enter_file (d->name);
+      d->name = NULL;
+      d->ignore_automatic_vars = 1;
+    }
+
+  return prereqs;
+}
+
+/* Perform per-file snap operations. */
 
 static void
-reset_updating (const void *item)
+snap_file (const void *item, void *arg)
 {
-  struct file *f = (struct file *) item;
+  struct file *f = (struct file*)item;
-  f->updating = 0;
+  struct dep *prereqs = NULL;
+
+  /* If we're not doing second expansion then reset updating.  */
+  if (!second_expansion)
+    f->updating = 0;
+
+  /* If .SECONDARY is set with no deps, mark all targets as intermediate.  */
+  if (all_secondary)
+    f->intermediate = 1;
+
+  /* If .EXTRA_PREREQS is set, add them as ignored by automatic variables.  */
+  if (f->variables)
+    prereqs = expand_extra_prereqs (lookup_variable_in_set (STRING_SIZE_TUPLE(".EXTRA_PREREQS"), f->variables->set));
+
+  else if (f->is_target)
+    prereqs = copy_dep_chain (arg);
+
+  if (prereqs)
+    {
+      struct dep *d;
+      for (d = prereqs; d; d = d->next)
+        if (streq (f->name, dep_name (d)))
+          /* Skip circular dependencies.  */
+          break;
+
+      if (d)
+        /* We broke early: must have found a circular dependency.  */
+        free_dep_chain (prereqs);
+      else if (!f->deps)
+        f->deps = prereqs;
+      else
+        {
+          d = f->deps;
+          while (d->next)
+            d = d->next;
+          d->next = prereqs;
+        }
+    }
 }
 
 /* For each dependency of each file, make the 'struct dep' point
@@ -700,9 +747,6 @@ snap_deps (void)
             expand_deps (f);
       free (file_slot_0);
     }
-  else
-    /* We're not doing second expansion, so reset updating.  */
-    hash_map (&files, reset_updating);
 
   /* Now manage all the special targets.  */
 
@@ -744,10 +788,7 @@ snap_deps (void)
           f2->intermediate = f2->secondary = 1;
     /* .SECONDARY with no deps listed marks *all* files that way.  */
     else
-      {
+      all_secondary = 1;
-        all_secondary = 1;
-        hash_map (&files, set_intermediate);
-      }
 
   f = lookup_file (".EXPORT_ALL_VARIABLES");
   if (f != 0 && f->is_target)
@@ -779,6 +820,15 @@ snap_deps (void)
   if (f != 0 && f->is_target)
     not_parallel = 1;
 
+  {
+    struct dep *prereqs = expand_extra_prereqs (lookup_variable (STRING_SIZE_TUPLE(".EXTRA_PREREQS")));
+
+    /* Perform per-file snap operations.  */
+    hash_map_arg(&files, snap_file, prereqs);
+
+    free_dep_chain (prereqs);
+  }
+
 #ifndef NO_MINUS_C_MINUS_O
   /* If .POSIX was defined, remove OUTPUT_OPTION to comply.  */
   /* This needs more work: what if the user sets this in the makefile?

src/filedef.h

@@ -21,6 +21,11 @@ this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
 #include "hash.h"
 
+struct commands;
+struct dep;
+struct variable;
+struct variable_set_list;
+
 struct file
   {
     const char *name;
@@ -110,6 +115,7 @@ 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);
+struct dep *expand_extra_prereqs (const struct variable *extra);
 void remove_intermediates (int sig);
 void snap_deps (void);
 void rename_file (struct file *file, const char *name);

src/implicit.c

@@ -152,6 +152,7 @@ struct patdeps
     const char *pattern;
     struct file *file;
     unsigned int ignore_mtime : 1;
+    unsigned int ignore_automatic_vars : 1;
   };
 
 /* This structure stores information about pattern rules that we need
@@ -564,6 +565,7 @@ pattern_search (struct file *file, int archive,
                     {
                       ++deps_found;
                       d->ignore_mtime = dep->ignore_mtime;
+                      d->ignore_automatic_vars = dep->ignore_automatic_vars;
                     }
 
                   /* We've used up this dep, so next time get a new one.  */
@@ -723,6 +725,7 @@ pattern_search (struct file *file, int archive,
 
                   memset (pat, '\0', sizeof (struct patdeps));
                   pat->ignore_mtime = d->ignore_mtime;
+                  pat->ignore_automatic_vars = d->ignore_automatic_vars;
 
                   DBS (DB_IMPLICIT,
                        (is_rule
@@ -913,6 +916,7 @@ pattern_search (struct file *file, int archive,
 
       dep = alloc_dep ();
       dep->ignore_mtime = pat->ignore_mtime;
+      dep->ignore_automatic_vars = pat->ignore_automatic_vars;
       s = strcache_add (pat->name);
       if (recursions)
         dep->name = s;

src/main.c

@@ -1313,7 +1313,7 @@ main (int argc, char **argv, char **envp)
   {
     const char *features = "target-specific order-only second-expansion"
                            " else-if shortest-stem undefine oneshell nocomment"
-                           " grouped-target"
+                           " grouped-target extra-prereqs"
 #ifndef NO_ARCHIVES
                            " archives"
 #endif
@@ -2134,9 +2134,9 @@ main (int argc, char **argv, char **envp)
 
   install_default_implicit_rules ();
 
-  /* Compute implicit rule limits.  */
+  /* Compute implicit rule limits and do magic for pattern rules.  */
 
-  count_implicit_rule_limits ();
+  snap_implicit_rules ();
 
   /* Construct the listings of directories in VPATH lists.  */
 

src/rule.c

@@ -60,36 +60,43 @@ struct file *suffix_file;
 
 static size_t maxsuffix;
 
-/* Compute the maximum dependency length and maximum number of
+/* Compute the maximum dependency length and maximum number of dependencies of
-   dependencies of all implicit rules.  Also sets the subdir
+   all implicit rules.  Also sets the subdir flag for a rule when appropriate,
-   flag for a rule when appropriate, possibly removing the rule
+   possibly removing the rule completely when appropriate.
-   completely when appropriate.  */
+
+   Add any global EXTRA_PREREQS here as well.  */
 
 void
-count_implicit_rule_limits (void)
+snap_implicit_rules (void)
 {
-  char *name;
+  char *name = NULL;
-  size_t namelen;
+  size_t namelen = 0;
-  struct rule *rule;
+  struct dep *prereqs = expand_extra_prereqs (lookup_variable (STRING_SIZE_TUPLE(".EXTRA_PREREQS")));
+  unsigned int pre_deps = 0;
 
-  num_pattern_rules = max_pattern_targets = max_pattern_deps = 0;
   max_pattern_dep_length = 0;
 
-  name = 0;
+  for (struct dep *d = prereqs; d; d = d->next)
-  namelen = 0;
-  rule = pattern_rules;
-  while (rule != 0)
     {
-      unsigned int ndeps = 0;
+      size_t l = strlen (dep_name (d));
-      struct dep *dep;
+      if (l > max_pattern_dep_length)
-      struct rule *next = rule->next;
+        max_pattern_dep_length = l;
+      ++pre_deps;
+    }
+
+  num_pattern_rules = max_pattern_targets = max_pattern_deps = 0;
+
+  for (struct rule *rule = pattern_rules; rule; rule = rule->next)
+    {
+      unsigned int ndeps = pre_deps;
+      struct dep *lastdep = NULL;
 
       ++num_pattern_rules;
 
       if (rule->num > max_pattern_targets)
         max_pattern_targets = rule->num;
 
-      for (dep = rule->deps; dep != 0; dep = dep->next)
+      for (struct dep *dep = rule->deps; dep != 0; dep = dep->next)
         {
           const char *dname = dep_name (dep);
           size_t len = strlen (dname);
@@ -99,17 +106,20 @@ count_implicit_rule_limits (void)
           const char *p2;
           if (p == 0)
             p = strrchr (dname, ':');
-          p2 = p != 0 ? strchr (dname, '%') : 0;
+          p2 = p ? strchr (p, '%') : 0;
 #else
           const char *p = strrchr (dname, '/');
-          const char *p2 = p != 0 ? strchr (dname, '%') : 0;
+          const char *p2 = p ? strchr (p, '%') : 0;
 #endif
           ndeps++;
 
           if (len > max_pattern_dep_length)
             max_pattern_dep_length = len;
 
-          if (p != 0 && p2 > p)
+          if (!dep->next)
+            lastdep = dep;
+
+          if (p2)
             {
               /* There is a slash before the % in the dep name.
                  Extract the directory name.  */
@@ -134,13 +144,20 @@ count_implicit_rule_limits (void)
             dep->changed = 0;
         }
 
+      if (prereqs)
+        {
+          if (lastdep)
+            lastdep->next = copy_dep_chain (prereqs);
+          else
+            rule->deps = copy_dep_chain (prereqs);
+        }
+
       if (ndeps > max_pattern_deps)
         max_pattern_deps = ndeps;
-
-      rule = next;
     }
 
   free (name);
+  free_dep_chain (prereqs);
 }
 
 /* Create a pattern rule from a suffix rule.

src/rule.h

@@ -48,7 +48,7 @@ extern size_t max_pattern_dep_length;
 extern struct file *suffix_file;
 
 
-void count_implicit_rule_limits (void);
+void snap_implicit_rules (void);
 void convert_to_pattern (void);
 void install_pattern_rule (struct pspec *p, int terminal);
 void create_pattern_rule (const char **targets, const char **target_percents,

tests/scripts/variables/EXTRA_PREREQS

@@ -0,0 +1,151 @@
+#                                                                    -*-perl-*-
+
+$description = "Test the .EXTRA_PREREQS special variable.";
+$details = "";
+
+# Simple global .EXTRA_PREREQS and automatic variable settings
+run_make_test('
+.EXTRA_PREREQS = tick tack
+.PHONY: all
+all: ; @echo ${.EXTRA_PREREQS}/$@/$</$^/$?/$+/$|/$*/
+tick tack: ; @echo $@
+',
+              '', "tick\ntack\ntick tack/all///////\n");
+
+# Global .EXTRA_PREREQS and pattern rules
+run_make_test('
+.EXTRA_PREREQS = tick tack
+a%: ; @echo ${.EXTRA_PREREQS}/$@/$</$^/$?/$+/$|/$*/
+tick tack: ; @echo $@
+',
+              'all', "tick\ntack\ntick tack/all//////ll/\n");
+
+# Simple target-specific .EXTRA_PREREQS and automatic variable settings
+run_make_test('
+.PHONY: all
+all: ; @echo ${.EXTRA_PREREQS}/$@/$</$^/$?/$+/$|/$*/
+all: .EXTRA_PREREQS = tick tack
+tick tack: ; @echo $@
+',
+              '', "tick\ntack\ntick tack/all///////\n");
+
+# Simple pattern-specific .EXTRA_PREREQS and automatic variable settings
+# This is not currently supported :-/
+if (0) {
+    run_make_test('
+.PHONY: all
+all: ; @echo ${.EXTRA_PREREQS}/$@/$</$^/$?/$+/$|/$*/
+a%: .EXTRA_PREREQS = tick tack
+tick tack: ; @echo $@
+',
+                  '', "tick\ntack\ntick tack/all///////\n");
+}
+
+touch('hi');
+
+# Basic test target specific .EXTRA_PREREQS:
+run_make_test('
+DEPENDENCY_ONLY_PREREQUISITES = ho hey
+OTHER_PREREQUISITES := foo bar baz
+target: .EXTRA_PREREQS := hi ${DEPENDENCY_ONLY_PREREQUISITES}
+target: ${OTHER_PREREQUISITES} ; @echo ${.EXTRA_PREREQS} $^
+.PHONY: target ${DEPENDENCY_ONLY_PREREQUISITES} ${OTHER_PREREQUISITES}
+${DEPENDENCY_ONLY_PREREQUISITES} ${OTHER_PREREQUISITES}: ; @echo $@
+',
+              '', "foo\nbar\nbaz\nho\nhey\nhi ho hey foo bar baz\n");
+
+# Test target specific .EXTRA_PREREQS and pattern rules:
+run_make_test('
+all: target.dst
+DEPENDENCY_ONLY_PREREQUISITES = ho hey
+target.dst: .EXTRA_PREREQS := hi ${DEPENDENCY_ONLY_PREREQUISITES}
+%.dst: %.src ; @echo ${.EXTRA_PREREQS} $^
+.PHONY: ${DEPENDENCY_ONLY_PREREQUISITES} target.src
+${DEPENDENCY_ONLY_PREREQUISITES} target.src: ; @echo $@
+',
+              '', "target.src\nho\nhey\nhi ho hey target.src\n");
+
+# Test that global .EXTRA_PREREQS are built first:
+run_make_test('
+.EXTRA_PREREQS = hi ho hey
+OTHER_PREREQUISITES := foo bar baz
+target: ${OTHER_PREREQUISITES} ; @echo ${.EXTRA_PREREQS} $^
+.PHONY: target ${.EXTRA_PREREQS} ${OTHER_PREREQUISITES}
+${.EXTRA_PREREQS} ${OTHER_PREREQUISITES}: ; @echo $@
+',
+              '', "hi\nho\nhey\nfoo\nbar\nbaz\nhi ho hey foo bar baz\n");
+
+# Test that target specific .EXTRA_PREREQS override global .EXTRA_PREREQS:
+run_make_test('
+.EXTRA_PREREQS = tick tack
+DEPENDENCY_ONLY_PREREQUISITES = ho hey
+OTHER_PREREQUISITES := foo bar baz
+target: .EXTRA_PREREQS := hi ${DEPENDENCY_ONLY_PREREQUISITES}
+target: ${OTHER_PREREQUISITES} ; @echo ${.EXTRA_PREREQS} $^
+.PHONY: target ${DEPENDENCY_ONLY_PREREQUISITES} ${OTHER_PREREQUISITES} ${.EXTRA_PREREQS}
+${DEPENDENCY_ONLY_PREREQUISITES} ${OTHER_PREREQUISITES} ${.EXTRA_PREREQS}: ; @echo $@
+',
+              '', "tick\ntack\nfoo\nbar\nbaz\nho\nhey\nhi ho hey foo bar baz\n");
+
+# Cleanup:
+unlink('hi');
+
+# Test error reporting of global .EXTRA_PREREQS:
+run_make_test('
+.EXTRA_PREREQS = tick tack
+.PHONY: all
+all: ; @echo ${.EXTRA_PREREQS} $^
+',
+              '', "#MAKE#: *** No rule to make target 'tick', needed by 'all'.  Stop.", 512);
+
+# Test error reporting of global .EXTRA_PREREQS and keep-going:
+run_make_test('
+.EXTRA_PREREQS = tick tack
+.PHONY: all
+all: ; @echo ${.EXTRA_PREREQS} $^
+',
+              '-k', "#MAKE#: *** No rule to make target 'tick', needed by 'all'.\n#MAKE#: *** No rule to make target 'tack', needed by 'all'.\n#MAKE#: Target 'all' not remade because of errors.", 512);
+
+# Test error reporting of target specific .EXTRA_PREREQS and keep-going:
+run_make_test('
+all: .EXTRA_PREREQS = tick tack
+.PHONY: all
+all: ; @echo ${.EXTRA_PREREQS} $^
+',
+              '-k',
+              "#MAKE#: *** No rule to make target 'tick', needed by 'all'.
+#MAKE#: *** No rule to make target 'tack', needed by 'all'.
+#MAKE#: Target 'all' not remade because of errors.\n", 512);
+
+# Test wildcard
+
+touch('tick', 'tack');
+
+run_make_test('
+.EXTRA_PREREQS = *ck
+.PHONY: all tick tack
+all: ; @echo ${.EXTRA_PREREQS} $^
+tick tack: ; @echo $@
+',
+              '', "tack\ntick\ntack tick\n");
+
+run_make_test('
+.PHONY: all tick tack
+all: ; @echo ${.EXTRA_PREREQS} $^
+all: .EXTRA_PREREQS = *ck
+tick tack: ; @echo $@
+',
+              '', "tack\ntick\ntack tick\n");
+
+run_make_test('
+.PHONY: tick tack
+a%: ; @echo ${.EXTRA_PREREQS} $^
+.EXTRA_PREREQS = *ck
+tick tack: ; @echo $@
+',
+              'all', "tack\ntick\ntack tick\n");
+
+unlink('tick', 'tack');
+
+# This tells the test driver that the perl test script executed properly.
+1;