Bug 462451: Don't be confused by .deps dirs in the source tree. r=bsmedberg

$(MDDEPDIR) needs to be created in the build tree, but if make rules
list $(MDDEPDIR) as a dependency, then the VPATH search will tend to
find dependency directories in source trees if the source tree has
been configured in the past.  So use $(CURDIR)/$(MDDEPDIR) instead.

Some directory Makefiles have been adding $(MDDEPDIR) to MAKE_DIRS and
GARBAGE_DIRS explicitly, since they're not setting any of the
variables that would cause config/rules.mk to create $(MDDEPDIR)
automatically.  Those makefiles would have to use the $(CURDIR) trick
to defeat the VPATH search, too.  Instead, have rules.mk check an
additional variable NEED_MDDEPDIRS, and let the makefiles set that;
this keeps the magic in one place.

config/Makefile.in

@@ -62,8 +62,8 @@ TARGETS		= $(HOST_PROGRAM) $(PLSRCS:.pl=) $(SIMPLE_PROGRAMS)
 ifndef CROSS_COMPILE
 ifdef USE_ELF_DYNSTR_GC
 TARGETS		+= elf-dynstr-gc
-MAKE_DIRS	+= $(MDDEPDIR)
-GARBAGE_DIRS	+= $(MDDEPDIR)
+# Compiling the above will create dependency files.
+NEED_MDDEPDIR	= 1
 endif
 endif
 

config/rules.mk

@@ -396,8 +396,10 @@ HOST_PROGOBJS		= $(HOST_OBJS)
 endif
 
 # MAKE_DIRS: List of directories to build while looping over directories.
-ifneq (,$(OBJS)$(XPIDLSRCS)$(SDK_XPIDLSRCS)$(SIMPLE_PROGRAMS))
-MAKE_DIRS		+= $(MDDEPDIR)
+# A Makefile that needs $(MDDEPDIR) created but doesn't set any of these
+# variables we know to check can just set NEED_MDDEPDIR explicitly.
+ifneq (,$(OBJS)$(XPIDLSRCS)$(SDK_XPIDLSRCS)$(SIMPLE_PROGRAMS)$(NEED_MDDEPDIR))
+MAKE_DIRS		+= $(CURDIR)/$(MDDEPDIR)
 GARBAGE_DIRS		+= $(MDDEPDIR)
 endif
 
@@ -2041,7 +2043,13 @@ endif # COMPILER_DEPEND
 #   builds (-jN). If this were done in the LOOP_OVER_DIRS macro, two
 #   processes could simultaneously try to create the same directory.
 #
-$(MDDEPDIR):
+#   We use $(CURDIR) in the rule's target to ensure that we don't find
+#   a dependency directory in the source tree via VPATH (perhaps from
+#   a previous build in the source tree) and thus neglect to create a
+#   dependency directory in the object directory, where we really need
+#   it.
+
+$(CURDIR)/$(MDDEPDIR):
 	@if test ! -d $@; then echo Creating $@; rm -rf $@; mkdir $@; else true; fi
 
 ifneq (,$(filter-out all chrome default export realchrome tools clean clobber clobber_all distclean realclean,$(MAKECMDGOALS)))

js/src/config/rules.mk

@@ -396,8 +396,10 @@ HOST_PROGOBJS		= $(HOST_OBJS)
 endif
 
 # MAKE_DIRS: List of directories to build while looping over directories.
-ifneq (,$(OBJS)$(XPIDLSRCS)$(SDK_XPIDLSRCS)$(SIMPLE_PROGRAMS))
-MAKE_DIRS		+= $(MDDEPDIR)
+# A Makefile that needs $(MDDEPDIR) created but doesn't set any of these
+# variables we know to check can just set NEED_MDDEPDIR explicitly.
+ifneq (,$(OBJS)$(XPIDLSRCS)$(SDK_XPIDLSRCS)$(SIMPLE_PROGRAMS)$(NEED_MDDEPDIR))
+MAKE_DIRS		+= $(CURDIR)/$(MDDEPDIR)
 GARBAGE_DIRS		+= $(MDDEPDIR)
 endif
 
@@ -2041,7 +2043,13 @@ endif # COMPILER_DEPEND
 #   builds (-jN). If this were done in the LOOP_OVER_DIRS macro, two
 #   processes could simultaneously try to create the same directory.
 #
-$(MDDEPDIR):
+#   We use $(CURDIR) in the rule's target to ensure that we don't find
+#   a dependency directory in the source tree via VPATH (perhaps from
+#   a previous build in the source tree) and thus neglect to create a
+#   dependency directory in the object directory, where we really need
+#   it.
+
+$(CURDIR)/$(MDDEPDIR):
 	@if test ! -d $@; then echo Creating $@; rm -rf $@; mkdir $@; else true; fi
 
 ifneq (,$(filter-out all chrome default export realchrome tools clean clobber clobber_all distclean realclean,$(MAKECMDGOALS)))

xpcom/tests/static-checker/Makefile.in

@@ -41,9 +41,8 @@ topsrcdir = @top_srcdir@
 srcdir = @srcdir@
 VPATH = @srcdir@
 
-# MAKE_DIRS: List of directories to build while looping over directories.
-MAKE_DIRS               += $(MDDEPDIR)
-GARBAGE_DIRS            += $(MDDEPDIR)
+# We will do compilations that create dependency files.
+NEED_MDDEPDIR = 1
 
 include $(DEPTH)/config/autoconf.mk