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Avoid accessing legacy TLV fields after the TLV-stream read #3622

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Merged
merged 1 commit into from
Feb 26, 2025
Merged

Avoid accessing legacy TLV fields after the TLV-stream read #3622

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6 changes: 3 additions & 3 deletions lightning-macros/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -246,8 +246,8 @@ pub fn skip_legacy_fields(expr: TokenStream) -> TokenStream {
/// Is expected to wrap a struct definition like
/// ```ignore
/// drop_legacy_field_definition!(Self {
/// field1: $crate::_ignore_arg!(field1, option),
/// field2: $crate::_ignore_arg!(field2, (legacy, u64, {})),
/// field1: $crate::_init_tlv_based_struct_field!(field1, option),
/// field2: $crate::_init_tlv_based_struct_field!(field2, (legacy, u64, {})),
/// })
/// ```
/// and will drop fields defined like `field2` with a type starting with `legacy`.
Expand Down Expand Up @@ -277,7 +277,7 @@ pub fn drop_legacy_field_definition(expr: TokenStream) -> TokenStream {
for field in new_fields {
if let syn::Expr::Macro(syn::ExprMacro { mac, .. }) = &field.expr {
let macro_name = mac.path.segments.last().unwrap().ident.to_string();
let is_init = macro_name == "_ignore_arg";
let is_init = macro_name == "_init_tlv_based_struct_field";
// Skip `field_name` and `:`, giving us just the type's group
let ty_tokens = mac.tokens.clone().into_iter().skip(2).next();
if let Some(proc_macro2::TokenTree::Group(group)) = ty_tokens {
Expand Down
23 changes: 1 addition & 22 deletions lightning/src/util/ser_macros.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -894,17 +894,6 @@ macro_rules! _init_and_read_tlv_stream {
}
}

/// Dummy macro that drops the second argument (which is used by
/// [`lightning_macros::drop_legacy_field_definition`] to match for legacy fields but isn't needed
/// in the final code we want to generate).
#[doc(hidden)]
#[macro_export]
macro_rules! _ignore_arg {
($field: ident, $fieldty: tt) => {
$field
};
}

/// Reads a TLV stream with the given fields to build a struct/enum variant of type `$thing`
#[doc(hidden)]
#[macro_export]
Expand All @@ -913,18 +902,8 @@ macro_rules! _decode_and_build {
$crate::_init_and_read_len_prefixed_tlv_fields!($stream, {
$(($type, $field, $fieldty)),*
});
// rustc is kinda dumb about unused variable warnings when we declare a variable via an
// ident in a macro and then use it in an expr also defined in the same macro call. Thus,
// it may generate unused variable warnings for variables that are, in fact, very much
// used. Instead, we just blanket ignore unused variables here as it may be useful to write
// field names without a _ prefix for legacy fields even if we don't care about the read
// value.
$(
#[allow(unused_variables)]
let $field = $crate::_init_tlv_based_struct_field!($field, $fieldty);
)*
::lightning_macros::drop_legacy_field_definition!($thing {
$($field: $crate::_ignore_arg!($field, $fieldty)),*
$($field: $crate::_init_tlv_based_struct_field!($field, $fieldty)),*
})
} }
}
Expand Down
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