[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]

These email responses aren't getting captured by phabricator.  Should they?

On Thu, Jul 13, 2017 at 1:07 PM, David Blaikie <dblaikie at gmail.com> wrote:

> I'm OK if this already does the right thing - but would like to know that,
> if you could check :) Otherwise, yeah, adding the empty-test would be good,
> I would think.
>
> On Thu, Jul 13, 2017 at 1:03 PM don hinton <hintonda at gmail.com> wrote:
>
>> 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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