[Buildroot] ccache problem when compiling with different toolchains in different projects

[Arnout Vandecappelle <arnout@mind.be>]

On 19/04/13 13:41, Mathias De Mar? wrote:
>
> wouldn't an alternative possibility be to change the CCACHE_COMPILERCHECK to:
> export CCACHE_COMPILERCHECK=%compiler% -v
>
> You don't rely on the timestamp that way, but you still have a check. I
> believe this resolves the clearing of ccache also (see also
> http://lists.busybox.net/pipermail/buildroot/2012-March/051187.html ).

  That sounds like a very good idea!

  It still has a few shortcomings, but it's definitely better than the 
current situation. At least the following are not solved yet.

- Options included in the external toolchain wrapper are not included. 
For instance, if you switch to Thumb on the Sourcery ARM toolchain, that 
will be recorded in the additional cflags in the wrapper and won't be 
visible to ccache.

- The output of gcc -v contains the absolute path, so if you change the 
output directory (or share the ccache between several developers) it 
won't work. But it would be feasible to strip off the $(O) part.

- For internal/crosstool-NG toolchains, when toolchain parameters are 
changed this is still not detected. For instance, some configure script 
checks for wchar, it fails, you change your configuration to include 
WCHAR and rebuild, and it still fails because the cached test is used...


  The ideal is still what I mentioned a year ago [1]: make a hash of the 
toolchain configuration part of the buildroot config. Too complex, unless 
we do a big rename of the relevant options into BR2_TOOLCHAIN_...
and grep them out of the config.


  Regards,
  Arnout


[1]
    http://lists.busybox.net/pipermail/buildroot/2012-February/049998.html

-- 
Arnout Vandecappelle                          arnout at mind be
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