On 5/3/21 10:10 PM, Ludovic Courtès wrote:
> Hi Tom,
> 
> Tom de Vries <tdevries@suse.de> skribis:
> 
>> The fact that libguile tries to set the libgmp memory functions is a bug which
>> should be fixed starting version v3.0.6.
> 
> Yes.  Building Guile with mini-GMP is recommended in 3.0.6 and later.
> 
>> +++ b/gdb/guile/guile.c
>> @@ -662,10 +662,32 @@ gdbscm_initialize (const struct extension_language_defn *extlang)
>>    {
>>      gdb::block_signals blocker;
>>  
>> +    /* There are libguile versions (f.i. v3.0.5) that by default call
>> +       mp_get_memory_functions during initialization to install custom
>> +       libgmp memory functions.  This is considered a bug and should be
>> +       fixed starting v3.0.6.
>> +       Before gdb commit 880ae75a2b7 "gdb delay guile initialization until
>> +       gdbscm_finish_initialization", that bug had no effect for gdb,
>> +       because gdb subsequently called mp_get_memory_functions to install
>> +       its own custom functions in _initialize_gmp_utils.  However, since
>> +       aforementioned gdb commit the initialization order is reversed,
>> +       allowing libguile to install a custom malloc that is incompatible
>> +       with the custom free as used in gmp-utils.c, resulting in a
>> +       "double free or corruption (out)" error.
>> +       Work around the libguile bug by saving the libgmp memory functions
>> +       before guile initialization, and restoring them afterwards.  */
>> +    void *(*alloc_func) (size_t);
>> +    void *(*realloc_func) (void *, size_t, size_t);
>> +    void (*free_func) (void *, size_t);
>> +    mp_get_memory_functions (&alloc_func, &realloc_func, &free_func);
>> +
>>      /* scm_with_guile is the most portable way to initialize Guile.  Plus
>>         we need to initialize the Guile support while in Guile mode (e.g.,
>>         called from within a call to scm_with_guile).  */
>>      scm_with_guile (call_initialize_gdb_module, NULL);
>> +
>> +    /* Restore libgmp memory functions.  */
>> +    mp_set_memory_functions (alloc_func, realloc_func, free_func);
> 
> This code would lead to memory leaks because Guile would still think it
> has its memory functions installed so it would never explicitly free GMP
> memory.
> 
> Instead, you can do:
> 
>   scm_install_gmp_memory_functions = 0;
> 
> before the first call to ‘scm_with_guile’.  That works with 3.0, 2.2,
> and 2.0.
> 
> HTH!

It does, thanks for the review :)

Committed as below.

Thanks,
- Tom