config: explain CONFIG_TYPE_EXTENDED

Also add an explanation of a possible future refactoring where we
might remove the config_type_t enumeration entierly.

Fixes ticket 31624.

No changes file, since this is a comment-only change.
This commit is contained in:
Nick Mathewson 2019-09-04 11:54:42 -04:00
parent 34f3fcef40
commit 03ce67d378

View File

@ -63,8 +63,17 @@ typedef enum config_type_t {
* context-sensitive config lines when fetching.
*/
CONFIG_TYPE_OBSOLETE, /**< Obsolete (ignored) option. */
CONFIG_TYPE_EXTENDED, /**< Extended type; definition will appear in
* pointer. */
/**
* Extended type: definition appears in the <b>type_def</b> pointer
* of the corresponding struct_member_t.
*
* For some types, we cannot define them as particular values of this
* enumeration, since those types are abstractions defined at a higher level
* than this module. (For example, parsing a routerset_t is higher-level
* than this module.) To handle this, we use CONFIG_TYPE_EXTENDED for those
* types, and give a definition for them in the struct_member_t.type_def.
**/
CONFIG_TYPE_EXTENDED,
} config_type_t;
/* Forward delcaration for var_type_def_t, for extended types. */
@ -74,15 +83,26 @@ struct var_type_def_t;
typedef struct struct_member_t {
/** Name of the field. */
const char *name;
/** Type of the field, according to the config_type_t enumeration.
/**
* Type of the field, according to the config_type_t enumeration.
*
* This value is CONFIG_TYPE_EXTENDED for any type not listed in
* config_type_t.
* For any type not otherwise listed in config_type_t, this field's value
* should be CONFIG_TYPE_EXTENDED. When it is, the <b>type_def</b> pointer
* must be set.
**/
/*
* NOTE: In future refactoring, we might remove this field entirely, along
* with its corresponding enumeration. In that case, we will require that
* type_def be set in all cases. If we do, we will also need a new mechanism
* to enforce consistency between configuration variable types and their
* corresponding structures, since our current design in
* lib/conf/conftesting.h won't work any more.
*/
config_type_t type;
/**
* Pointer to a type definition for the type of this field. Overrides
* <b>type</b> if not NULL.
* <b>type</b> if it is not NULL. Must be set when <b>type</b> is
* CONFIG_TYPE_EXTENDED.
**/
const struct var_type_def_t *type_def;
/**