Re: [RFC,PATCH] Do not GC_INIT the Boehm GC if already initialized

[Jose E. Marchesi]

> On 06/02/2023 19:34, Jose E. Marchesi wrote:
>> 
>> Hello Guile hackers.
>> 
>> We are in the process of integrating GNU poke[1] in GDB by mean of
>> libpoke.
>> 
>> Problem is, libpoke uses the Boehm GC, as guile does.  We are working on
>> switching to an ad-hoc exact collector, but it will get some time.
>> 
>> So, in the interim, we may:
>> 
>> 1) Make both libguile and libpoke to do GC_INIT conditionally, only if
>>    no one else has initialized the collector before.  This is already in
>>    poke master.  A suggested (untested!) patch for guile below.
>> 
>> 2) Test to see if the collector works properly.
>> 
>> 3) Do bug-fix releases of both libguile and libpoke so the GDB people
>>    can check for the right version in configure.ac in order to allow
>>    configuring GDB with both libpoke and libguile support.
>> 
>> Does this sound like a plan?
>> Thanks in advance!
>> 
>> [1] https://jemarch.net/poke
>> 
>> diff --git a/libguile/gc.c b/libguile/gc.c
>> index 7717e9bef..36653d373 100644
>> --- a/libguile/gc.c
>> +++ b/libguile/gc.c
>> @@ -462,7 +462,8 @@ scm_storage_prehistory ()
>>    setenv ("GC_MARKERS", "1", 1);
>>  #endif
>>  
>> -  GC_INIT ();
>> +  if(!GC_is_init_called ())
>> +    GC_INIT ();
>>  
>>    size_t heap_size = GC_get_heap_size ();
>>    if (heap_size < DEFAULT_INITIAL_HEAP_SIZE)
>> 
>
>
>
> Isn't that going to cause problems if the configurations clash?
> For example, the scm_storage_prehistory () function that you
> are modifying does
>
> GC_set_all_interior_pointers (0);
>
> If the application that previously initialized the GC relies
> on interior pointer tracing, Guile disabling it is going to
> cause trouble.

Indeed, we would need to agree on these details and come with a
configuration that works with both configurations.