Re: [PATCH] Fix thread-unsafe lazy initializations

[ludo@gnu.org (Ludovic Courtès)]

Mark H Weaver <mhw@netris.org> skribis:

> From dadcb1512569c1be039fc75f0a2967e370939e42 Mon Sep 17 00:00:00 2001
> From: Mark H Weaver <mhw@netris.org>
> Date: Thu, 28 Feb 2013 17:56:58 -0500
> Subject: [PATCH] Fix thread-unsafe lazy initializations.
>
> * libguile/debug.c (scm_local_eval):
>   libguile/ports.c (scm_current_warning_port):
>   libguile/strports.c (scm_eval_string_in_module): Perform
>   lazy-initialization while holding a mutex.  Use SCM_UNDEFINED as the
>   uninitialized value.  Use 'scm_c_*_variable'.
>
> * doc/ref/api-modules.texi (Accessing Modules from C): Fix
>   'my_eval_string' example to be thread-safe.

Looks good to me.

> --- a/doc/ref/api-modules.texi
> +++ b/doc/ref/api-modules.texi
> @@ -942,14 +942,15 @@ the @var{name} is not bound in the module, signals an error.  Returns a
>  variable, always.
>  
>  @example
> -SCM my_eval_string (SCM str)
> -@{
> -  static SCM eval_string_var = SCM_BOOL_F;
> +static SCM eval_string_var;
>  
> -  if (scm_is_false (eval_string_var))
> -    eval_string_var =
> -      scm_c_public_lookup ("ice-9 eval-string", "eval-string");
> +void my_init (void)
> +@{
> +  eval_string_var = scm_c_public_lookup ("ice-9 eval-string", "eval-string");
> +@}
>  
> +SCM my_eval_string (SCM str)
> +@{
>    return scm_call_1 (scm_variable_ref (eval_string_var), str);
>  @}
>  @end example

The doc should say something about ‘my_init’, and perhaps mention
locking?

Ludo’.