ccache directory not being created

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

Dear Dan Moulding,

Thanks for your report and investigation! Some comments below.

This is not done anywhere, because ccache creates the directory for its cache, but it does not recursively creates the parent directories for it. So as long as the parent directory of the specified cache directory exists, then ccache will create it automatically.

It does seem like a good idea to me to ensure that the cache directory exists before actually using ccache, in order to properly support custom BR2_CCACHE_DIR configurations, such as yours.

Best regards,

Thomas

Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com