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Fix thread-unsafe lazy initializations.

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* 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.
This commit is contained in:
Mark H Weaver 2013-02-28 17:56:58 -05:00
parent 29ace173b1
commit f57ea23ac8
4 changed files with 29 additions and 14 deletions
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16
doc/ref/api-modules.texi
View file

@ -945,14 +945,18 @@ the @var{name} is not bound in the module, signals an error. Returns a
variable, always. variable, always.
@example @example
static SCM eval_string_var;
/* NOTE: It is important that the call to 'my_init'
happens-before all calls to 'my_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) SCM my_eval_string (SCM str)
@{ @{
static SCM eval_string_var = SCM_BOOL_F;
if (scm_is_false (eval_string_var))
eval_string_var =
scm_c_public_lookup ("ice-9 eval-string", "eval-string");
return scm_call_1 (scm_variable_ref (eval_string_var), str); return scm_call_1 (scm_variable_ref (eval_string_var), str);
@} @}
@end example @end example

8
libguile/debug.c
View file

@ -211,10 +211,14 @@ SCM_DEFINE (scm_debug_hang, "debug-hang", 0, 1, 0,
SCM SCM
scm_local_eval (SCM exp, SCM env) scm_local_eval (SCM exp, SCM env)
{ {
static SCM local_eval_var = SCM_BOOL_F; static SCM local_eval_var = SCM_UNDEFINED;
static scm_i_pthread_mutex_t local_eval_var_mutex
= SCM_I_PTHREAD_MUTEX_INITIALIZER;
if (scm_is_false (local_eval_var)) scm_i_scm_pthread_mutex_lock (&local_eval_var_mutex);
if (SCM_UNBNDP (local_eval_var))
local_eval_var = scm_c_public_variable ("ice-9 local-eval", "local-eval"); local_eval_var = scm_c_public_variable ("ice-9 local-eval", "local-eval");
scm_i_pthread_mutex_unlock (&local_eval_var_mutex);
return scm_call_2 (SCM_VARIABLE_REF (local_eval_var), exp, env); return scm_call_2 (SCM_VARIABLE_REF (local_eval_var), exp, env);
} }

10
libguile/ports.c
View file

@ -418,10 +418,14 @@ SCM_DEFINE (scm_current_error_port, "current-error-port", 0, 0, 0,
SCM SCM
scm_current_warning_port (void) scm_current_warning_port (void)
{ {
static SCM cwp_var = SCM_BOOL_F; static SCM cwp_var = SCM_UNDEFINED;
static scm_i_pthread_mutex_t cwp_var_mutex
= SCM_I_PTHREAD_MUTEX_INITIALIZER;
if (scm_is_false (cwp_var)) scm_i_scm_pthread_mutex_lock (&cwp_var_mutex);
cwp_var = scm_c_private_lookup ("guile", "current-warning-port"); if (SCM_UNBNDP (cwp_var))
cwp_var = scm_c_private_variable ("guile", "current-warning-port");
scm_i_pthread_mutex_unlock (&cwp_var_mutex);
return scm_call_0 (scm_variable_ref (cwp_var)); return scm_call_0 (scm_variable_ref (cwp_var));
} }

9
libguile/strports.c
View file

@ -534,13 +534,16 @@ SCM_DEFINE (scm_eval_string_in_module, "eval-string", 1, 1, 0,
"procedure returns.") "procedure returns.")
#define FUNC_NAME s_scm_eval_string_in_module #define FUNC_NAME s_scm_eval_string_in_module
{ {
static SCM eval_string = SCM_BOOL_F, k_module = SCM_BOOL_F; static SCM eval_string = SCM_UNDEFINED, k_module = SCM_UNDEFINED;
static scm_i_pthread_mutex_t init_mutex = SCM_I_PTHREAD_MUTEX_INITIALIZER;
if (scm_is_false (eval_string)) scm_i_scm_pthread_mutex_lock (&init_mutex);
if (SCM_UNBNDP (eval_string))
{ {
eval_string = scm_c_public_lookup ("ice-9 eval-string", "eval-string"); eval_string = scm_c_public_variable ("ice-9 eval-string", "eval-string");
k_module = scm_from_locale_keyword ("module"); k_module = scm_from_locale_keyword ("module");
} }
scm_i_pthread_mutex_unlock (&init_mutex);
if (SCM_UNBNDP (module)) if (SCM_UNBNDP (module))
module = scm_current_module (); module = scm_current_module ();