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LibertyXDR: add support for default in unions

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This commit is contained in:
Přemysl Eric Janouch 2025-05-07 19:42:46 +02:00
parent 9a26284a64
commit b69d3f8692
Signed by: p
GPG Key ID: A0420B94F92B9493
3 changed files with 30 additions and 7 deletions
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6
libertyxdr.adoc
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@ -93,10 +93,12 @@ and always-present field, which must be a tag *enum*:
case CAR: void;
case LORRY: i8 axles;
case PLANE: i8 engines;
default: void;
};
All possible enumeration values must be named, and there is no *case*
fall-through.
There is no *case* fall-through.
Unless *default* is present, only the listed enumeration values are valid.
Any *default* must currently be empty.
Framing
-------

2
tests/lxdrgen.lxdr
View File

@ -25,5 +25,7 @@ struct Struct {
union Onion switch (Enum tag) {
case NOTHING:
void;
default:
void;
} o;
};

29
tools/lxdrgen.awk
View File

@ -1,6 +1,6 @@
# lxdrgen.awk: an XDR-derived code generator for network protocols.
#
# Copyright (c) 2022 - 2023, Přemysl Eric Janouch <p@janouch.name>
# Copyright (c) 2022 - 2025, Přemysl Eric Janouch <p@janouch.name>
# SPDX-License-Identifier: 0BSD
#
# Usage: env LC_ALL=C awk -f lxdrgen.awk -f lxdrgen-{c,go,mjs}.awk \
@ -218,7 +218,7 @@ function defstruct( name, d, cg) {
}
function defunion( name, tag, tagtype, tagvalue, cg, scg, d, a, i,
unseen, exhaustive) {
unseen, defaulted, exhaustive) {
delete cg[0]
delete scg[0]
delete d[0]
@ -249,9 +249,22 @@ function defunion( name, tag, tagtype, tagvalue, cg, scg, d, a, i,
if (!unseen[tagvalue]--)
fatal("no such value or duplicate case: " tagtype "." tagvalue)
codegen_struct_tag(tag, scg)
} else if (accept("default")) {
if (tagvalue)
codegen_union_struct(name, tagvalue, cg, scg)
expect(accept(":"))
if (defaulted)
fatal("duplicate default")
tagvalue = ""
defaulted = 1
} else if (tagvalue) {
if (readfield(d))
codegen_struct_field(d, scg)
} else if (defaulted) {
if (readfield(d))
fatal("default must not contain fields")
} else {
fatal("union fields must fall under a case")
}
@ -259,11 +272,17 @@ function defunion( name, tag, tagtype, tagvalue, cg, scg, d, a, i,
if (tagvalue)
codegen_union_struct(name, tagvalue, cg, scg)
# Unseen cases are simply not recognized/allowed.
# Unseen cases are only recognized/allowed when default is present.
exhaustive = 1
for (i in unseen)
if (i && unseen[i])
exhaustive = 0
if (i && unseen[i]) {
if (defaulted) {
codegen_struct_tag(tag, scg)
codegen_union_struct(name, i, cg, scg)
} else {
exhaustive = 0
}
}
Types[name] = "union"
codegen_union(name, cg, exhaustive)