[PATCH] D35377: [CMAKE] PR33717 When LLVM_APPEND_VC_REV = OFF, only create VCSRevision.h if it doesn't already exist.

[don hinton via llvm-commits]

I think so, but we could also check to see if it's empty.  That way you'll
always have an empty file if it's OFF.

On Thu, Jul 13, 2017 at 12:51 PM, David Blaikie <dblaikie at gmail.com> wrote:

> Does this do the correct/desired thing if LLVM_APPEND_VC_REV is changed
> from ON to OFF - or does it leave the last rev in the file indefinitely?
> That could eb confusing to developers.
>
>
> On Thu, Jul 13, 2017 at 12:40 PM don hinton via Phabricator <
> reviews at reviews.llvm.org> wrote:
>
>> hintonda created this revision.
>> Herald added a subscriber: mgorny.
>>
>> If LLVM_APPEND_VC_REV = OFF, find_first_existing_vc_file will
>> not set llvm_vc and VCSRevision.h will be rewritten every time cmake
>> is run, which causes everything VCSRevision.h depends on to get
>> rebuilt and relinked even if nothing else changed.
>>
>>
>> https://reviews.llvm.org/D35377
>>
>> Files:
>>   include/llvm/Support/CMakeLists.txt
>>
>>
>> Index: include/llvm/Support/CMakeLists.txt
>> ===================================================================
>> --- include/llvm/Support/CMakeLists.txt
>> +++ include/llvm/Support/CMakeLists.txt
>> @@ -55,7 +55,9 @@
>>      PROPERTIES GENERATED TRUE
>>                 HEADER_FILE_ONLY TRUE)
>>  else()
>> -  file(WRITE "${version_inc}" "")
>> +  if(NOT EXISTS "${version_inc}")
>> +    file(WRITE "${version_inc}" "")
>> +       endif()
>>  endif()
>>
>>  add_custom_target(llvm_vcsrevision_h DEPENDS "${version_inc}")
>>
>>
>>
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