ccache: set COMPILERCHECK to 'none'

This allows ccache to re-use its cache contents even if the compiler
binary mtime has changed. It is the simplest approach to solve this
problem, and it works for the internal, external and crosstool-ng
toolchain backends.

Of course, it leaves the user responsible for invalidating the cache
when necessary, but there doesn't seem to be a real good solution that
allows both to: 1/ keep the cache contents accross builds and re-use
it and 2/ invalidate the cache automatically when the compiler chances
in an incompatible way.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

diff --git a/Config.in b/Config.in
index 8579a63b1884114fe3b56decf120015388dd595c..2002996fe3de63dc509bf094c36c67bb53c7f33f 100644 (file)
--- a/Config.in
+++ b/Config.in
@@ -191,6 +191,13 @@ config BR2_CCACHE
          up future builds. The cache is stored in
          $HOME/.buildroot-ccache.
 
+         Note that Buildroot does not try to invalidate the cache
+         contents when the compiler changes in an incompatible
+         way. Therefore, if you make a change to the compiler version
+         and/or configuration, you are responsible for purging the
+         ccache cache by removing the $HOME/.buildroot-ccache
+         directory.
+
 config BR2_DEPRECATED
        bool "Show packages that are deprecated or obsolete"
        help

diff --git a/package/ccache/ccache.mk b/package/ccache/ccache.mk
index 393989f546f4639f063919937ed84233e81853ba..f71376ee8528ece435458aff754df9083faa38bc 100644 (file)
--- a/package/ccache/ccache.mk
+++ b/package/ccache/ccache.mk
@@ -25,10 +25,18 @@ HOST_CCACHE_CONF_ENV = \
 # has zero dependency besides the C library.
 HOST_CCACHE_CONF_OPT += ccache_cv_zlib_1_2_3=no
 
-# We directly hardcode the cache location into the binary, as it is
-# much easier to handle than passing an environment variable.
+# We directly hardcode configuration into the binary, as it is much
+# easier to handle than passing an environment variable. Our
+# configuration is:
+#  - the cache location
+#  - the fact that ccache shouldn't use the compiler binary mtime to
+#  - detect a change in the compiler, because in the context of
+#  - Buildroot, that completely defeats the purpose of ccache. Of
+#  - course, that leaves the user responsible for purging its cache
+#  - when the compiler changes.
 define HOST_CCACHE_FIX_CCACHE_DIR
        sed -i 's,getenv("CCACHE_DIR"),"$(CCACHE_CACHE_DIR)",' $(@D)/ccache.c
+       sed -i 's,getenv("CCACHE_COMPILERCHECK"),"none",' $(@D)/ccache.c
 endef
 
 HOST_CCACHE_POST_CONFIGURE_HOOKS += \