From b959655822df6c5610372c9da54ea93f93ac87e9 Mon Sep 17 00:00:00 2001
From: Amaury Pouly <amaury.pouly@gmail.com>
Date: Fri, 12 May 2017 19:50:56 +1000
Subject: Fix unsafe substitutions in Makefile.

Strange things can happen in the (unlikely) case that ROOTDIR=/rockbox

Change-Id: I085f928fd859b307667e8fccf40b29a9c325f7ae
---
 tools/functions.make | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

(limited to 'tools/functions.make')

diff --git a/tools/functions.make b/tools/functions.make
index 2a26e48bf2..806e1a2f3e 100644
--- a/tools/functions.make
+++ b/tools/functions.make
@@ -73,3 +73,18 @@ ifeq ($(call info),old)
 export info=echo "$$(1)";
 endif
 
+# path substituion can be surprisingly tricky, indeed the following almost
+# always work but not quite:
+#   BMPOBJ = $(BMP:$(ROOTDIR)/%.bmp=$(BUILDDIR)/%.o)
+# indeed if
+#   ROOTDIR=/rockbox
+#   BUILDDIR=/rockbox/build-bla
+# then:
+#   /rockbox/apps/bitmaps/rockboxlogo-bla.bmp -> /rockbox/apps/bitmaps/rockbox/build-blalogo.o
+# this function ensure that this type of problems does not occur
+#
+# usage: $(call full_path_subst,patterm,replacement,text)
+#
+# example: $(call full_path_subst,$(ROOTDIR)/%.bmp,$(BUILDDIR)/%.o,$(BMP))
+NO_MATCH=this_string_will_never_match_anything
+full_path_subst=$(patsubst $(NO_MATCH)/%,%, $(patsubst $(NO_MATCH)/$(1), $(2), $(addprefix $(NO_MATCH)/, $(3))))
-- 
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