.Fd size_t cdecl_explain(char *buf, size_t n, struct cdecl *decl);
.Fd size_t cdecl_declare(char *buf, size_t n, struct cdecl *decl);
.Pp
+.Fd const struct cdecl_error *cdecl_get_error(void);
+.Pp
.Fd int cdecl_spec_kind(struct cdecl_declspec *spec);
+.Fd bool cdecl_is_abstract(struct cdecl_declarator *declarator);
.Sh DESCRIPTION
.Nm
provides support for parsing C declarations and translating them to something
is intended to be portable to any system with a working C implementation that
at least makes an effort to support C99. The library is thread-safe when
appropriate facilities exist and are enabled at build time.
+.Sh NAMESPACE
+.Nm
+reserves all identifiers beginning with either
+.Li cdecl_
+or
+.Li CDECL_
+in both the tag and ordinary identifier namespaces. All external names
+beginning with
+.Li cdecl_
+are reserved, and the library headers may define object-like macros beginning
+with
+.Li CDECL_ .
+The
+.Nm
+library headers may use other identifiers where they do not pollute the global
+namespaces, such as struct members or function parameter names. Such internal
+identifiers shall not contain any upper-case letters. As these internal
+identifiers can only conflict with object-like macros, this practice is safe as
+long as the convention of defining object-like macros using upper-case letters
+is adhered to.
+.Pp
+External names beginning with
+.Li cdecl
+followed by two consecutive underscores are not considered part of the ABI and
+are thus subject to change at any time.
.Sh ABSTRACT SYNTAX TREE
The functions in
.Nm
.El
.Ss Terminal Declarators
Null and identifier declarators have no children and are thus leaf nodes. A
-null declarator indicates an abstract declarator; that is, one which does not
-declare any identifier. Such declarators appear in type names and possibly
-function parameters. An identifier declarator has the obvious meaning; the
+null declarator is not strictly a C language construct, but is used by
+.Nm
+to indicate an abstract declarator; that is, one which does not declare any
+identifier. Such declarators appear in type names and possibly function
+parameters. An identifier declarator has the obvious meaning; the
.Va ident
union member points to the C string containing the identifier.
+.Pp
+Since a null declarator may be deeply nested in the declarator chain, the
+function
+.Pp
+.Fd bool cdecl_is_abstract(struct cdecl_declarator *declarator);
+.Pp
+can be used to determine whether or not a given declarator declares an
+identifier. The result is true if and only if the declarator is abstract.
.Ss Pointer Declarators
.Bd -literal -offset indent
struct cdecl_pointer {
otherwise). If
.Va variadic
is true, then the function is variadic.
+.Pp
+Note that old-style function declarations with non-empty identifier lists are
+not directly represented here: this is because they are syntactically identical
+to a prototype where every parameter is a typedef name. Since
+.Nm
+isn't a C compiler, there is no way for the parser to tell these two kinds of
+declarations apart.
+.Sh ERROR HANDLING
+Some functions in
+.Nm
+can fail. Such functions will be documented as indicating an error condition
+in a particular way. It is sometimes necessary to know more about a particular
+error in order to print an informative error message or perform some other
+action. To facilitate this,
+.Nm
+provides a structure which describes a particular error.
+.Bd -literal -offset indent
+struct cdecl_error {
+ unsigned code;
+ const char *str;
+};
+.Ed
+.Pp
+The
+.Va code
+member identifies the sort of error which has occurred, while the
+.Va str
+member points to a string containing a human-readable description of the error.
+This error information can be retrieved by calling the function
+.Pp
+.Fd const struct cdecl_error *cdecl_get_error(void);
+.Pp
+which returns a pointer to the error structure most recently generated in the
+current thread. It is therefore thread-safe in that errors occurring in
+another thread will not interfere with the current one. The returned pointer
+shall remain valid until the next call to any function from
+.Nm
+by the same thread, except that multiple consecutive calls to
+.Va cdecl_get_error
+shall all return the same value. The same applies to the
+.Va str
+pointer inside the error structure itself.
+.Pp
+If this function is called before an error has been indicated by an earlier
+call in the same thread, the behaviour is undefined.
.Sh PARSING DECLARATIONS
To parse a declaration, the function
.Pp
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