I may find the reason why it crash.Please read the comment in the code.
int gphoto_read_widget(gphoto_widget *widget)
{
char *ptr=NULL;
int i;
int ret = GP_OK;
switch(widget->type) {
case GP_WIDGET_TEXT:
/* some code here */
case GP_WIDGET_RADIO:
case GP_WIDGET_MENU:
ret = gp_widget_get_value (widget->widget, &ptr);
/* the first time precessing the whitebiaspresetno widget, ret = GP_OK, and ptr still NULL */
if (ret != GP_OK)
return ret;
if (! widget->choices) {
widget->choice_cnt = gp_widget_count_choices (widget->widget);
widget->choices = calloc(sizeof(char *), widget->choice_cnt + 1);
/* allocate memery */
for ( i=0; i<widget->choice_cnt; i++) {
const char *choice=NULL;
ret = gp_widget_get_choice (widget->widget, i, &choice);
/ * ret = GP_OK and choice = "0" */
if (ret != GP_OK)
return ret;
if (ptr && choice)
{
if (strcmp(choice, ptr) == 0)
widget->value.index = i;
widget->choices[i] = choice;
}
else
return GP_ERROR;
/* ptr = NULL, so return GP_ERROR, but widget->choices is not NULL */
}
}
break;
case GP_WIDGET_DATE:
ret = gp_widget_get_value (widget->widget, &widget->value.date);
break;
default:
fprintf(stderr, "WARNING: Widget type: %d is unsupported\n", widget->type);
}
return ret;
}
Back to here:
gphoto_widget *gphoto_get_widget_info(gphoto_driver *gphoto, gphoto_widget_list **iter)
{
gphoto_widget *widget;
if(! *iter)
return NULL;
widget = (*iter)->widget;
int ret = gphoto_read_widget(widget);
/* ret = GP_ERROR */
if (ret == GP_OK)
{
*iter=(*iter)->next;
return widget;
}
else
return NULL;
/* so iter still point to whitbiaspresetno widget */
}
The next time call
int gphoto_read_widget(gphoto_widget *widget)
{
char *ptr=NULL;
int i;
int ret = GP_OK;
switch(widget->type) {
case GP_WIDGET_TEXT:
/* some code here */
case GP_WIDGET_RADIO:
case GP_WIDGET_MENU:
ret = gp_widget_get_value (widget->widget, &ptr);
/* the second time precessing the whitebiaspresetno widget, ret = GP_OK, and ptr still NULL */
if (ret != GP_OK)
return ret;
/* the last time widget whitbiaspresetno's choices's memery is allocated , but value of choices[0] is 0x0 */
/* this time func will directly return ret value, GP_OK */
if (! widget->choices) {
widget->choice_cnt = gp_widget_count_choices (widget->widget);
widget->choices = calloc(sizeof(char *), widget->choice_cnt + 1);
for ( i=0; i<widget->choice_cnt; i++) {
const char *choice=NULL;
ret = gp_widget_get_choice (widget->widget, i, &choice);
if (ret != GP_OK)
return ret;
if (ptr && choice)
{
if (strcmp(choice, ptr) == 0)
widget->value.index = i;
widget->choices[i] = choice;
}
else
return GP_ERROR;
}
}
break;
case GP_WIDGET_DATE:
ret = gp_widget_get_value (widget->widget, &widget->value.date);
break;
default:
fprintf(stderr, "WARNING: Widget type: %d is unsupported\n", widget->type);
}
return ret;
}
So, in func gphoto_get_widget_info, iter will move to the next widget and return a widget with choices[0] = 0x0, this cause create_switch func fail.
this may solve the problem
gphoto_widget *gphoto_get_widget_info(gphoto_driver *gphoto, gphoto_widget_list **iter)
{
gphoto_widget *widget;
if(! *iter)
return NULL;
widget = (*iter)->widget;
int ret = gphoto_read_widget(widget);
*iter=(*iter)->next;
if (ret == GP_OK)
{
return widget;
}
else
return NULL;
}
