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Show HN: Cdecl-dump - represent C declarations visually

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Re: Show HN: Cdecl-dump - represent C declarations visually

#11

Post by userbinator »

pcfwik wrote: post #3

Since this is about C declarations: for anyone who (like me) had the misfortune of learning the so-called "spiral rule" in college rather than being taught how declarations in C work, below are some links that explain the "declaration follows use" idea that (AFAIK) is the true philosophy behind C declaration syntax (and significantly easier to remember/read/write). TL;DR: you declare a variable in C _in exactly the s…

if you know how to use a variable, then you know how to read and write a declaration for it.

In other words, the precedence of operators in a declaration have exactly the same precedence as in its use.

Re: Show HN: Cdecl-dump - represent C declarations visually

#12

Post by korianders »

nitrix wrote: post #7
saagarjha wrote: post #6

Earlier quoted context omitted.

Of course, the correct way to use a function pointer is to call it.

Yes, the () operator dereference function pointers automatically for you for convenience. There's also the surprise that you can infinitely dereference function pointers as they just yield you more function pointers.

One baffling thing I see people do with typedefing function pointers is insisting on adding in the pointer part in the typedef which just complicates and hides things.

If you want to typedef a function pointer, make a completely ordinary function declaration, then slap 'typedef' at the beginning, done. This does require you to do "foo_func *f" instead of "foo_func f" when declaring variables, but that is just clearer imo.

    typedef int foo_func(int); // nice

    typedef int (*foo_func)(int); // why?

Re: Show HN: Cdecl-dump - represent C declarations visually

#13

Post by xvilka »

We use the tree-sitter[1] for parsing C declarations in Rizin[2] (see the "td" command, for example). See our custom grammar[3] (modified mainstream tree-sitter-c). The custom grammar was sadly necessary, due to the inability of Tree-Sitter to have the alternate roots[4].

P.S. Please add a license for your code.

[1] https://tree-sitter.github.io/

[2] https://github.com/rizinorg/rizin/tree/dev/librz/type/parser

[3] https://github.com/rizinorg/rizin-grammar-c/

[4] https://github.com/tree-sitter/tree-sitter/issues/711

Re: Show HN: Cdecl-dump - represent C declarations visually

#14

Post by cryptonector »

korianders wrote: post #12
nitrix wrote: post #7

Earlier quoted context omitted.

Yes, the () operator dereference function pointers automatically for you for convenience. There's also the surprise that you can infinitely dereference function pointers as they just yield you more function pointers.

One baffling thing I see people do with typedefing function pointers is insisting on adding in the pointer part in the typedef which just complicates and hides things. If you want to typedef a function pointer, make a completely ordinary function declaration, then slap 'typedef' at the beginning, done. This does require you to do "foo_func *f" instead of "foo_func f" when declaring variables, but that is just clearer…

Why do you need the `*` to be part of every variable/member declaration?

Re: Show HN: Cdecl-dump - represent C declarations visually

#15

Post by coherentpony »

bluetomcat wrote: post #4
coherentpony wrote: post #2

I don’t understand what the visualisation screenshot in the README is trying to communicate to me.

It starts from the identifier. At every stage, it outputs a sub-expression which is the “mirrored use” and corresponds to the boxed representation below it. When it reaches the top of the expression, it prints the final type of the expression which is the lone specifier-qualifier list. As per the screenshot, “arr” is an array of 4 elements. Consequently, “arr[0]” is an array of 8 elements. Then, “arr[0][0]” is a poin…

Ok that helps. Thank you.
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