[Qemu-devel] [PATCH] configure: disallow ccache during compile tests

[Qemu-devel] [PATCH] configure: disallow ccache during compile tests

[John Snow]

If the user is using CCACHE during the configuration step,
it may interfere with some of the configuration tests,
particularly the "Is CCACHE interfering with macro analysis" step,
which is a bit of a poetic problem.

1) Disallow CCACHE from reading from the cache during configure,
   but don't disable it to allow us to see if it causes other problems.

2) Force off CCACHE_CPP2 during the ccache test to get a deterministic
   answer over whether or not we need to enable that feature later.

Signed-off-by: John Snow <jsnow@redhat.com>
---
 configure | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/configure b/configure
index 7a1d08d..9c726eb 100755
--- a/configure
+++ b/configure
@@ -8,6 +8,9 @@
 CLICOLOR_FORCE= GREP_OPTIONS=
 unset CLICOLOR_FORCE GREP_OPTIONS
 
+# Don't allow CCACHE, if present, to use cached results of compile tests!
+export CCACHE_RECACHE=yes
+
 # Temporary directory used for files created while
 # configure runs. Since it is in the build directory
 # we can safely blow away any previous version of it
@@ -4412,6 +4415,7 @@ fi
 # check if ccache is interfering with
 # semantic analysis of macros
 
+unset CCACHE_CPP2
 ccache_cpp2=no
 cat > $TMPC << EOF
 static const int Z = 1;
-- 
2.4.3

Re: [Qemu-devel] [PATCH] configure: disallow ccache during compile tests

[Markus Armbruster]

John Snow <jsnow@redhat.com> writes:

> If the user is using CCACHE during the configuration step,
> it may interfere with some of the configuration tests,
> particularly the "Is CCACHE interfering with macro analysis" step,
> which is a bit of a poetic problem.
>
> 1) Disallow CCACHE from reading from the cache during configure,
>    but don't disable it to allow us to see if it causes other problems.

This is confusing.  "don't disable it entirely"?

> 2) Force off CCACHE_CPP2 during the ccache test to get a deterministic
>    answer over whether or not we need to enable that feature later.
>
> Signed-off-by: John Snow <jsnow@redhat.com>

Re: [Qemu-devel] [PATCH] configure: disallow ccache during compile tests

[John Snow]

On 10/29/2015 02:17 AM, Markus Armbruster wrote:
> John Snow <jsnow@redhat.com> writes:
> 
>> If the user is using CCACHE during the configuration step,
>> it may interfere with some of the configuration tests,
>> particularly the "Is CCACHE interfering with macro analysis" step,
>> which is a bit of a poetic problem.
>>
>> 1) Disallow CCACHE from reading from the cache during configure,
>>    but don't disable it to allow us to see if it causes other problems.
> 
> This is confusing.  "don't disable it entirely"?
> 

We allow it to submit items into the cache, but not to read items from
the cache. This prevents it from picking up cached results to the
compile tests.

I don't disable it entirely (just pass-through to the real compiler
without using ccache at all) because I still want to allow ccache to be
processing things to test for ccache failures -- particularly the ccache
macro check that occurs later.

If I just disable ccache, that later check is meaningless. Setting the
cache to "write only" gives me the best of both worlds.

>> 2) Force off CCACHE_CPP2 during the ccache test to get a deterministic
>>    answer over whether or not we need to enable that feature later.
>>
>> Signed-off-by: John Snow <jsnow@redhat.com>

Re: [Qemu-devel] [PATCH] configure: disallow ccache during compile tests

[Markus Armbruster]

John Snow <jsnow@redhat.com> writes:

> On 10/29/2015 02:17 AM, Markus Armbruster wrote:
>> John Snow <jsnow@redhat.com> writes:
>> 
>>> If the user is using CCACHE during the configuration step,
>>> it may interfere with some of the configuration tests,
>>> particularly the "Is CCACHE interfering with macro analysis" step,
>>> which is a bit of a poetic problem.
>>>
>>> 1) Disallow CCACHE from reading from the cache during configure,
>>>    but don't disable it to allow us to see if it causes other problems.
>> 
>> This is confusing.  "don't disable it entirely"?
>> 
>
> We allow it to submit items into the cache, but not to read items from
> the cache. This prevents it from picking up cached results to the
> compile tests.
>
> I don't disable it entirely (just pass-through to the real compiler
> without using ccache at all) because I still want to allow ccache to be
> processing things to test for ccache failures -- particularly the ccache
> macro check that occurs later.
>
> If I just disable ccache, that later check is meaningless. Setting the
> cache to "write only" gives me the best of both worlds.

All right, shows that I can confuse with the best of them!

It took my a moment to understand what "disallow but don't disable"
means.  I think inserting "entirely" into your sentence right after
"disable it" makes it easier to understand.

>>> 2) Force off CCACHE_CPP2 during the ccache test to get a deterministic
>>>    answer over whether or not we need to enable that feature later.
>>>
>>> Signed-off-by: John Snow <jsnow@redhat.com>

Re: [Qemu-devel] [PATCH] configure: disallow ccache during compile tests

[Paolo Bonzini]

On 29/10/2015 17:22, Markus Armbruster wrote:
> John Snow <jsnow@redhat.com> writes:
> 
>> On 10/29/2015 02:17 AM, Markus Armbruster wrote:
>>> John Snow <jsnow@redhat.com> writes:
>>>
>>>> If the user is using CCACHE during the configuration step,
>>>> it may interfere with some of the configuration tests,
>>>> particularly the "Is CCACHE interfering with macro analysis" step,
>>>> which is a bit of a poetic problem.
>>>>
>>>> 1) Disallow CCACHE from reading from the cache during configure,
>>>>    but don't disable it to allow us to see if it causes other problems.
>>>
>>> This is confusing.  "don't disable it entirely"?
>>>
>>
>> We allow it to submit items into the cache, but not to read items from
>> the cache. This prevents it from picking up cached results to the
>> compile tests.
>>
>> I don't disable it entirely (just pass-through to the real compiler
>> without using ccache at all) because I still want to allow ccache to be
>> processing things to test for ccache failures -- particularly the ccache
>> macro check that occurs later.
>>
>> If I just disable ccache, that later check is meaningless. Setting the
>> cache to "write only" gives me the best of both worlds.
> 
> All right, shows that I can confuse with the best of them!
> 
> It took my a moment to understand what "disallow but don't disable"
> means.  I think inserting "entirely" into your sentence right after
> "disable it" makes it easier to understand.

Ok, commit log adjusted.

Paolo

Re: [Qemu-devel] [PATCH] configure: disallow ccache during compile tests

[Paolo Bonzini]

On 28/10/2015 18:56, John Snow wrote:
> If the user is using CCACHE during the configuration step,
> it may interfere with some of the configuration tests,
> particularly the "Is CCACHE interfering with macro analysis" step,
> which is a bit of a poetic problem.
> 
> 1) Disallow CCACHE from reading from the cache during configure,
>    but don't disable it to allow us to see if it causes other problems.
> 
> 2) Force off CCACHE_CPP2 during the ccache test to get a deterministic
>    answer over whether or not we need to enable that feature later.
> 
> Signed-off-by: John Snow <jsnow@redhat.com>
> ---
>  configure | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/configure b/configure
> index 7a1d08d..9c726eb 100755
> --- a/configure
> +++ b/configure
> @@ -8,6 +8,9 @@
>  CLICOLOR_FORCE= GREP_OPTIONS=
>  unset CLICOLOR_FORCE GREP_OPTIONS
>  
> +# Don't allow CCACHE, if present, to use cached results of compile tests!
> +export CCACHE_RECACHE=yes
> +
>  # Temporary directory used for files created while
>  # configure runs. Since it is in the build directory
>  # we can safely blow away any previous version of it
> @@ -4412,6 +4415,7 @@ fi
>  # check if ccache is interfering with
>  # semantic analysis of macros
>  
> +unset CCACHE_CPP2
>  ccache_cpp2=no
>  cat > $TMPC << EOF
>  static const int Z = 1;
> 

Queued, thanks.