RFR: 8044797 Building with clang gives: fatal error: file '...' has been modified since the precompiled header was built

[Staffan Larsen]

On 5 jun 2014, at 13:38, David Holmes <david.holmes at oracle.com> wrote:

> On 4/06/2014 11:54 PM, Staffan Larsen wrote:
>> When building with clang and changing a file that is part of the precompiled header, you can get:
>> 
>> fatal error: file '/Users/staffan/mercurial/jdk9-hs-rt/hotspot/src/share/vm/runtime/thread.hpp' has been modified since the precompiled header was built
>> 
>> clang behaves differently than gcc here.
> 
> You mean clang reports an error when regenerating the pch file? That seems like a bug to me.

Yes. It also deletes the files, so rerunning the same command again succeeds...

> 
> Deleting the file first seems quite reasonable.

Thanks.

/Staffan

> 
> Thanks,
> David
> 
>> Example with clang:
>> 
>> $ ls
>> test.h
>> $ cat test.h
>> #include <stdio.h>
>> $ clang -x c-header -include test.h test.h -o test.h.pch
>> $ touch test.h
>> $ clang -x c-header -include test.h test.h -o test.h.pch
>> fatal error: file '/Users/staffan/tmp/pch/test.h' has been modified since the precompiled header was built
>> 1 error generated.
>> 
>> Same with gcc:
>> 
>> $ ls
>> test.h
>> $ cat test.h
>> #include <stdio.h>
>> $ gcc -x c-header -include test.h test.h -o test.h.pch
>> $ touch test.h
>> $ gcc -x c-header -include test.h test.h -o test.h.pch
>> 
>> 
>> The proposed fix is to delete the .pch file before calling clang or gcc.
>> 
>> diff --git a/make/bsd/makefiles/vm.make b/make/bsd/makefiles/vm.make
>> --- a/make/bsd/makefiles/vm.make
>> +++ b/make/bsd/makefiles/vm.make
>> @@ -295,6 +295,7 @@
>>  $(PRECOMPILED_HEADER):
>>  	$(QUIETLY) echo Generating precompiled header $@
>>  	$(QUIETLY) mkdir -p $(PRECOMPILED_HEADER_DIR)
>> +	$(QUIETLY) rm -f $@
>>  	$(QUIETLY) $(COMPILE.CXX) $(DEPFLAGS) -x c++-header $(PRECOMPILED_HEADER_SRC) -o $@ $(COMPILE_DONE)
>> 
>>  # making the library:
>> 
>> 
>> Thanks,
>> /Staffan
>>