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Rec-descent absolutely does work (source: wrote a working parser), but it's a bit annoying to make it build a syntax tree. Making it build a prefix encoding of

Rec-descent absolutely does work (source: wrote a working parser), but it's a bit annoying to make it build a syntax tree. Making it build a prefix encoding of the declaration is much easier. If you have to, you can make a syntax tree work, too, but you'll have to thread through the declarator parser a double (triple?) pointer for the hole in the tree where the next part goes, and at the end plug it with the specifiers-and-qualifiers part you parsed before that. Or at least that's what I had working before I gave up and switched to a prefix code. It'd probably pay to check the LCC book (Fraser & Hanson, A Retargetable C Compiler: Design and Implementation) to see what they do there, because their type representation is in fact a hash-consed tree. (The LuaJIT FFI parser needs some sort of magic fix-up pass at the end that I didn't much like, but I don't remember the specifics.)

HexDecOctBin 2y ago
> Rec-descent absolutely does work (source: wrote a working parser), but it's a bit annoying to make it build a syntax tree. Yeah, it required too much backtracking and state snap-shotting and resets, and I couldn't figure out a decent way of reporting good errors. Thanks for the references. The code I have now is pretty elegant and functional, so I'm not in the mood of diving back into it. But if I ever need to change it, I'll take a look.
foldr 2y ago
I think the most straightforward recursive-descent approach is just to parse the expression part of the type as an expression and then turn it inside out to get the type. So if you have e.g. 'int (*(p[5]))(char)', then your parse tree is something like declaration int function call * [] p 5 char and you need to turn that inside out to get something like array pointer to function int (char) This way you have a simple expression parser combined with a simple recursive tree transformation function. (The tree transformation took about 50 LOC when I implemented it for a toy parser.)

HexDecOctBin 2y ago

> Rec-descent absolutely does work (source: wrote a working parser), but it's a bit annoying to make it build a syntax tree. Yeah, it required too much backtracking and state snap-shotting and resets, and I couldn't figure out a decent way of reporting good errors. Thanks for the references. The code I have now is pretty elegant and functional, so I'm not in the mood of diving back into it. But if I ever need to change it, I'll take a look.

foldr 2y ago

I think the most straightforward recursive-descent approach is just to parse the expression part of the type as an expression and then turn it inside out to get the type. So if you have e.g. 'int (*(p[5]))(char)', then your parse tree is something like declaration int function call * [] p 5 char and you need to turn that inside out to get something like array pointer to function int (char) This way you have a simple expression parser combined with a simple recursive tree transformation function. (The tree transformation took about 50 LOC when I implemented it for a toy parser.)