From d868c9c5c37d2a5fb03875eba54ca80a476d7edb Mon Sep 17 00:00:00 2001
From: Leandro Lanzieri <leandro.lanzieri@haw-hamburg.de>
Date: Thu, 28 Nov 2019 14:13:39 +0100
Subject: [PATCH 1/2] makefiles: Do not set CCACHE_BASEDIR environmental
 variable

When CCACHE_BASEDIR variable is set, ccache rewrites absolute paths into
relative paths before computing the hash that identifies the compilation
for all the paths under that directory.

The problem is that those paths are also used when the compiler is
called, so the generated dependency files (*.d) will have a relative
path to the object files, and thus, it will not match our rule for
compiling (we use absolute paths). As dependency files define the
targets this way, any change on its dependencies (e.g. an included
header file) will not re-trigger a build.
---
 Makefile.include      | 3 ---
 makefiles/vars.inc.mk | 3 ---
 2 files changed, 6 deletions(-)

diff --git a/Makefile.include b/Makefile.include
index cea7c51fab..5cfd10ccdc 100644
--- a/Makefile.include
+++ b/Makefile.include
@@ -23,7 +23,6 @@ include $(RIOT_MAKEFILES_GLOBAL_PRE)
 
 # set undefined variables
 RIOTBASE       ?= $(_riotbase)
-CCACHE_BASEDIR ?= $(RIOTBASE)
 RIOTCPU        ?= $(RIOTBASE)/cpu
 RIOTBOARD      ?= $(RIOTBASE)/boards
 RIOTMAKE       ?= $(RIOTBASE)/makefiles
@@ -55,7 +54,6 @@ __DIRECTORY_VARIABLES := \
   BUILD_DIR \
   BINDIRBASE \
   BINDIR \
-  CCACHE_BASEDIR \
   GITCACHE \
   PKGDIRBASE \
   DLCACHE_DIR \
@@ -63,7 +61,6 @@ __DIRECTORY_VARIABLES := \
 
 # Make all paths absolute.
 override RIOTBASE       := $(abspath $(RIOTBASE))
-override CCACHE_BASEDIR := $(abspath $(CCACHE_BASEDIR))
 override RIOTCPU        := $(abspath $(RIOTCPU))
 override RIOTBOARD      := $(abspath $(RIOTBOARD))
 override RIOTMAKE       := $(abspath $(RIOTMAKE))
diff --git a/makefiles/vars.inc.mk b/makefiles/vars.inc.mk
index 06b5b525f0..bc2732b496 100644
--- a/makefiles/vars.inc.mk
+++ b/makefiles/vars.inc.mk
@@ -92,9 +92,6 @@ export HEXFILE               # The 'intel hex' stripped result of the compilatio
 # RESET                      # The command to call on "make reset", this command resets/reboots the target.
 # RESET_FLAGS                # The parameters to supply to RESET.
 
-export CCACHE_BASEDIR        # ccache basedir, allows multiple riot build
-                             # directories to share a ccache directory
-
 export DLCACHE               # directory used to cache http downloads
 export DOWNLOAD_TO_FILE      # Use `$(DOWNLOAD_TO_FILE) $(DESTINATION) $(URL)` to download `$(URL)` to `$(DESTINATION)`.
 export DOWNLOAD_TO_STDOUT    # Use `$(DOWNLOAD_TO_STDOUT) $(URL)` to download `$(URL)` output `$(URL)` to stdout, e.g. to be piped into `tar xz`.

From dc845841f0f201d42c87b10da5faa8ba55ba113c Mon Sep 17 00:00:00 2001
From: Leandro Lanzieri <leandro.lanzieri@haw-hamburg.de>
Date: Thu, 28 Nov 2019 15:34:20 +0100
Subject: [PATCH 2/2] Makefile.base: Set targets of *.d files to absolute
 object path

By passing the -MT flag with the absolute path to the object we make
sure that the compiler generates dependency files with rules that match
our building rules.
---
 Makefile.base | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/Makefile.base b/Makefile.base
index f937603245..5f7fd9f02d 100644
--- a/Makefile.base
+++ b/Makefile.base
@@ -100,25 +100,25 @@ $(OBJC): $(BINDIR)/$(MODULE)/%.o: %.c $(RIOTBUILD_CONFIG_HEADER_C)
 	$(Q)$(CCACHE) $(CC) \
 		-DRIOT_FILE_RELATIVE=\"$(patsubst $(RIOTBASE)/%,%,$(abspath $<))\" \
 		-DRIOT_FILE_NOPATH=\"$(notdir $<)\" \
-		$(CFLAGS) $(INCLUDES) -MD -MP -c -o $@ $(abspath $<)
+		$(CFLAGS) $(INCLUDES) -MQ '$@' -MD -MP -c -o $@ $(abspath $<)
 
 $(GENOBJC): %.o: %.c $(RIOTBUILD_CONFIG_HEADER_C)
 	$(Q) $(CCACHE) $(CC) \
 		-DRIOT_FILE_RELATIVE=\"$(patsubst $(RIOTBASE)/%,%,$<)\" \
 		-DRIOT_FILE_NOPATH=\"$(notdir $<)\" \
-		$(CFLAGS) $(INCLUDES) -MD -MP -c -o $@ $<
+		$(CFLAGS) $(INCLUDES) -MQ '$@' -MD -MP -c -o $@ $<
 
 $(OBJCXX): $(BINDIR)/$(MODULE)/%.o: %.cpp $(RIOTBUILD_CONFIG_HEADER_C)
 	$(Q)$(CCACHE) $(CXX) \
 		-DRIOT_FILE_RELATIVE=\"$(patsubst $(RIOTBASE)/%,%,$(abspath $<))\" \
 		-DRIOT_FILE_NOPATH=\"$(notdir $<)\" \
-		$(CXXFLAGS) $(CXXINCLUDES) $(INCLUDES) -MD -MP -c -o $@ $(abspath $<)
+		$(CXXFLAGS) $(CXXINCLUDES) $(INCLUDES) -MQ '$@' -MD -MP -c -o $@ $(abspath $<)
 
 $(ASMOBJ): $(BINDIR)/$(MODULE)/%.o: %.s
 	$(Q)$(AS) $(ASFLAGS) -o $@ $(abspath $<)
 
 $(ASSMOBJ): $(BINDIR)/$(MODULE)/%.o: %.S $(RIOTBUILD_CONFIG_HEADER_C)
-	$(Q)$(CCAS) $(CCASFLAGS) $(INCLUDES) -MD -MP -c -o $@ $(abspath $<)
+	$(Q)$(CCAS) $(CCASFLAGS) $(INCLUDES) -MQ '$@' -MD -MP -c -o $@ $(abspath $<)
 
 # pull in dependency info for *existing* .o files
 # deleted header files will be silently ignored