[Buildroot] ccache directory not being created

[Dan Moulding <dan.moulding@rackwareinc.com>]

Hello,

I have experienced a problem where, with ccache enabled, and the cache directory set to a subdirectory within the buildroot output directory, the build fails because ccache is trying to write files to the cache directory, but the cache directory doesn't exist. Well, more precisely, ccache will create the cache directory itself, but the cache directory's parent directory does not exist and ccache will not create that.

The error I get, during host-binutils 2.24 configuration, is:

  checking for C compiler default output file name...
  configure: error: in `/home/dmoulding/rwi1/cai/buildroot/output/build/host-binutils-2.24':
  configure: error: C compiler cannot create executables
  See `config.log' for more details.
  make: *** [/home/dmoulding/rwi1/cai/buildroot/output/build/host-binutils-  2.24/.stamp_configured] Error 77

Examining config.log I see this:

  configure:4258: checking for C compiler default output file name
  configure:4280: /home/dmoulding/rwi1/cai/buildroot/output/host/usr/bin/ccache /usr/lib64/ccache/gcc -O2 -I/home/dmoulding/rwi1/cai/buildroot/output/host/usr/include -I/home/dmoulding/rwi1/cai/buildroot/output/host/usr/include -L/home/dmoulding/rwi1/cai/buildroot/output/host/lib -L/home/dmoulding/rwi1/cai/buildroot/output/host/usr/lib -Wl,-rpath,/home/dmoulding/rwi1/cai/buildroot/output/host/usr/lib conftest.c  >&5
  ccache: failed to create /home/dmoulding/rwi1/cai/buildroot/output/build/toolchain-undefined/ccache-3.1.8/cache (No such file or directory)
  configure:4284: $? = 1
  configure:4321: result: 
  configure: failed program was:
  | /* confdefs.h */
  | #define PACKAGE_NAME ""
  | #define PACKAGE_TARNAME ""
  | #define PACKAGE_VERSION ""
  | #define PACKAGE_STRING ""
  | #define PACKAGE_BUGREPORT ""
  | #define PACKAGE_URL ""
  | /* end confdefs.h.  */
  | 
  | int
  | main ()
  | {
  | 
  |   ;
  |   return 0;
  | }
  configure:4327: error: in `/home/dmoulding/rwi1/cai/buildroot/output/build/host-binutils-2.24':
  configure:4331: error: C compiler cannot create executables
  See `config.log' for more details.

Note that ccache is complaining that it cannot create the "cache" directory (the parent directory does not exist).
 
Relevant Buildroot configuration:

  BR2_CCACHE=y
  BR2_CCACHE_DIR="$(TOOLCHAIN_DIR)/ccache-$(CCACHE_VERSION)/cache"

Looking way back in buildroot's history, I see that in 2010 (commit 17b66af), the way ccache is managed was reworked. Prior to this rework, the ccache makefile used to "mkdir -p" the cache directory. I don't see anywhere in the current revision where the equivalent is being done.

For now, I have patched my package/ccache/ccache.mk to add a hook that does the "mkdir -p" step. Is this the right way to solve this problem, or have I overlooked something else?

Cheers,

-- Dan