serialization: support passing extra args to fields in DSL #9287
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This PR is upstreaming changes in the Seraphis lib here: UkoeHB#39. This header adds a macro `VA_ARGS_COMMAPREFIX` which, when passed `__VA_ARGS__`, expands to `, __VA_ARGS__` unless the length of `__VA_ARGS__` is 0, in which case it expands to nothing. This macro is useful for passing/declaring optional function arguments.
This PR is upstreaming changes in the Seraphis lib here: UkoeHB#39. The changes to the serialization header allow clean passing of extra arguments to field serialization in the DSL. This is used mainly to pass implied sizes of containers during deserialization to make the format more compact. For example, if my object has two containers A & B which must be the same size, I can serialize only the size of container A. Then, during deserialization, when I deserialize A, I can then use A's size to deserialize B. Depends on monero-project#9286.
| // front if more than one argument, else nothing. | ||
| // If __VA_OPT__ supported, use that. Else, use GCC's ,## hack | ||
| #if VA_OPT_SUPPORTED | ||
| # define VA_ARGS_COMMAPREFIX(...) __VA_OPT__(,) __VA_ARGS__ |
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Why even have this extra mode if the compatibility mode forces a 1+ argument anyway? Basically, you are limited by what the compatibility mode can do anyway.
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The compatibility mode shouldn't force a 1+ argument. __VA_OPT__(x) should expand to nothing if no variadic arguments are provided: https://gcc.gnu.org/onlinedocs/cpp/Variadic-Macros.html
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Yes but:
VA_ARGS_COMMAPREFIX(...) , ## __VA_ARGS__should have a dangling comma ?
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On GCC-style compilers , ## __VA_ARGS__ also expands to nothing if there are no variadic args.
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Ah yes, that's what the comment says.
| } \ | ||
| template <bool W, template <bool> class Archive> \ | ||
| bool do_serialize_object(Archive<W> &ar, stype &v) { \ | ||
| #define BEGIN_SERIALIZE_OBJECT_FN(stype, ...) \ |
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After the first argument, you have to list the typename and variable name? A little funky, but it works.
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Oops closed wrong one |
This PR is upstreaming changes in the Seraphis lib here: UkoeHB#39. The changes to the serialization header allow clean passing of extra arguments to field serialization in the DSL. This is used mainly to pass implied sizes of containers during deserialization to make the format more compact. For example, if my object has two containers A & B which must be the same size, I can serialize only the size of container A. Then, during deserialization, when I deserialize A, I can then use A's size to deserialize B.
Depends on #9286.