[Bug 245452] net-im/telegram-desktop: Fails to build with ccache: fatal error: file '*' has been modified since the precompiled header '*'

[bugzilla-noreply at freebsd.org]

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=245452

--- Comment #17 from Charlie Li <ml+freebsd at vishwin.info> ---
After hitting this problem with audio/audacity (which now uses cmake), this is
almost entirely a ccache implementation defect. What we're dealing with is how
clang handles precompiled headers, which is a bit different than how gcc does
it.

Some upstream threads for context:
https://gitlab.kitware.com/cmake/cmake/-/merge_requests/4400
https://github.com/ccache/ccache/issues/539
https://github.com/ccache/ccache/issues/549

With regard to PCHs in ccache generally, ccache(1) has a dedicated section
describing how to make it process PCHs properly (because it doesn't by
default). Quote the part that needs done in ccache.conf:

   ccache has support for GCC's precompiled headers. However, you have to
   do some things to make it work properly:

   o   You must set sloppiness to pch_defines,time_macros. The reason is
       that ccache can't tell whether __TIME__ or __DATE__ is used when
       using a precompiled header. Further, it can't detect changes in
       #defines in the source code because of how preprocessing works in
       combination with precompiled headers.

Once added, at least on my -CURRENT setup where base LLVM got updated since I
last built and cached this port, the error message changes to:

error: PCH file built from a different branch
((git at github.com:llvm/llvm-project.git llvmorg-10.0.0-129-gd24d5c8e308)) than
the comp
iler ((git at github.com:llvm/llvm-project.git llvmorg-10.0.1-rc2-0-g77d76b71d7d))

Further tests will need done to find other error messages, ie when base LLVM
stays the same.

-- 
You are receiving this mail because:
You are the assignee for the bug.