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asn1: Circular types and Topo. sort declarations

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Many external ASN.1 modules that we have imported over time define types
like this:

  Foo ::= SEQUENCE { bar Bar }
  Bar ::= SEQUENCE { aMember INTEGER }

and before this change one had to re-order the definitions so that the
one for `Bar` came first.  No more.

We can now have out of order definitions in ASN.1 modules and the
compiler will topologically sort output C type declarations so that one
no longer has to manually sort types in ASN.1 modules when importing
them.

Besides that, it is now possible to create circular data types using
OPTIONAL since we generate such fields as pointers (which can then be
pointers to incomplete struct declarations):

  Circular ::= SEQUENCE {
          name UTF8String,
          next Circular OPTIONAL
  }

Circular types aren't necessarily useful, but they have been used in the
past.  E.g., the rpc.mountd protocol uses a circular type as a linked
list -- it should just have used an array, of course, as that's
semantically equivalent but more space efficient in its encoding, but
the point is that such types exist out there.
This commit is contained in:
Nicolas Williams
2020-12-24 03:18:28 -06:00
parent 5b978c7437
commit 83d4c6ddb5
8 changed files with 367 additions and 30 deletions
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21
lib/asn1/main.c
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@@ -71,6 +71,7 @@ int one_code_file;
char *option_file;
int parse_units_flag = 1;
char *type_file_string = "krb5-types.h";
int original_order;
int version_flag;
int help_flag;
struct getargs args[] = {
@@ -88,7 +89,15 @@ struct getargs args[] = {
{ "preserve-binary", 0, arg_strings, &preserve, NULL, NULL },
{ "sequence", 0, arg_strings, &seq, NULL, NULL },
{ "one-code-file", 0, arg_flag, &one_code_file, NULL, NULL },
{ "option-file", 0, arg_string, &option_file, NULL, NULL },
{ "gen-name", 0, arg_string, &name,
"Name of generated module", "NAME" },
{ "option-file", 0, arg_string, &option_file,
"File with additional compiler CLI options", "FILE" },
{ "original-order", 0, arg_flag, &original_order,
"Define C types and functions in the order in which they appear in "
"the ASN.1 module instead of topologically sorting types. This "
"is useful for comparing output to earlier compiler versions.",
NULL },
{ "parse-units", 0, arg_negative_flag, &parse_units_flag, NULL, NULL },
{ "type-file", 0, arg_string, &type_file_string, NULL, NULL },
{ "version", 0, arg_flag, &version_flag, NULL, NULL },
@@ -116,11 +125,11 @@ main(int argc, char **argv)
int len = 0, i;
setprogname(argv[0]);
if(getarg(args, num_args, argc, argv, &optidx))
if (getarg(args, num_args, argc, argv, &optidx))
usage(1);
if(help_flag)
if (help_flag)
usage(0);
if(version_flag) {
if (version_flag) {
print_version(NULL);
exit(0);
}
@@ -204,7 +213,7 @@ main(int argc, char **argv)
}
init_generate (file, name);
init_generate(file, name);
if (one_code_file)
generate_header_of_codefile(name);
@@ -213,6 +222,8 @@ main(int argc, char **argv)
ret = yyparse ();
if(ret != 0 || error_flag != 0)
exit(1);
if (!original_order)
generate_types();
close_generate ();
if (argc != optidx)
fclose(yyin);