[slime-devel] unexpected behavior of eval-when with CCL when compiling with C-c C-k

[Faheem Mitha]

Hi Helmut,

Thanks very much for the detailed and helpful reply.

May I post this as an answer to the SO question? If you don't want to post 
it yourself, that is.

On Thu, 30 Aug 2012, Helmut Eller wrote:

> On Thu, Aug 30 2012, Faheem Mitha wrote:
>
>> Hi,
>>
>> I recently posted a question at
>>
>> http://stackoverflow.com/questions/12156902/unxpected-behavior-with-eval-when
>>
>> Brief summary:
>>
>> The following code should (I think) set *read-default-float-format* to
>> double float. Well, it does compile with C-c C-k, but running
>>
>> *read-default-float-format*
>>
>> in the REPL afterwards gives SINGLE-FLOAT.
>>
>> So the value of *read-default-float-format* in the REPL has not changed
>> from the default value of SINGLE-FLOAT.
>>
>> Note, however, that the
>>
>> (print *read-default-float-format*)
>>
>> in the code does return DOUBLE-FLOAT.
>>
>> Rainer Joswig, in his answer to this question, says that this is
>> because the compilation and the REPL are on different threads (if I
>> understand him correctly), but I'd like some evidence of this.
>
> SLIME creates a new thread for C-c C-k.  As compiling could potentially
> take a long time, using a new thread seems like a reasonable thing to
> do.  Therefore the code that compiles and loads your code is a different
> thread than the REPL thread.
>
> For evidence, evaluate (princ ccl:*current-process*) in the REPL and
> inside the eval-when form.

Ah. I tried the function "all-processes". *current-process* is better.

>> Also, this code works fine with SBCL.

>> In addition to wanting to understand why this is happening, I'd like
>> to know whether it is possible to work around this, and set
>> *read-default-float-format* in a file, rather than having to set it on
>> the command line.
>>
>> I'm not sure whether this issue has something to do with SLIME, so I'm
>> posting here first.
>>
>> Platform and versions. I'm using Debian squeeze x86. The version of
>> SLIME is from Debian unstable, 1:20120525-2. CCL is the 1.8 release. I
>> tried it both with the upstream binaries from
>> http://svn.clozure.com/publicsvn/openmcl/release/1.8/linuxx86/ccl, and
>> a binary package created by me - see Package ccl at
>> mentors.debian.net. The result was the same in each case.
>>
>> Thanks in advance. Please CC me on any reply.
>
> When CCL creates a new thread it binds some special variables in the new
> thread.  *READ-DEFAULT-FLOAT-FORMAT* is one of them.  You can see the
> full list of those variables with (ccl::standard-initial-bindings).
> Also look at the documentation of MAKE-PROCESS[1].  I think
> CCL:DEF-STANDARD-INITIAL-BINDING can be used to change those variables
> for future thread, but I know no easy way to change them in all existing
> threads.

When it says MAKE-PROCESS here, it actually means thread, right? This 
terminology is a little confusing.

The documentation says "See DEF-STANDARD-INITIAL-BINDING" but there is no 
further information about DEF-STANDARD-INITIAL-BINDING that I could find. 
It seems this is a function. I found one example of usage which looks like

  (ccl::def-standard-initial-binding *read-default-float-format* 'double-float)

Is this correct usage? So, this changes the default value of 
*read-default-float-format* for all future threads? Should this be called 
in CCL's init file or somewhere else?

One last question, which is tangentially related. Is there some easy way 
to find out what CCL (or, more generally, any CL implementation) function 
is called by C-c C-k?

                                                           Regards, Faheem

> Helmut
>
> [1] http://ccl.clozure.com/ccl-documentation.html#f_make-process