Comments on: Reading C type declarations

By: Miron Brezuleanu

Miron Brezuleanu — Wed, 30 Jul 2008 05:38:40 +0000

Thanks for the reply,

I’ve used this as a Haskell programming exercise.
http://haskell.pastebin.com/f4c0d351c

It ended up as a simple C->English cdecl.

Maybe you’re interested.

By: eliben

eliben — Sat, 19 Jul 2008 13:15:59 +0000

Miron,

This is called an “abstract declarator” in the jargon of K&R2, as opposed to a “declarator” which has a variable name.

1. Go into the innermost grouping parentheses. If there are none, ignore this step.
2. The virtual declarator would appear between the *s and the []s
3. Proceed decoding as a declarator.

By: Jestine Paul

Jestine Paul — Sat, 19 Jul 2008 07:35:43 +0000

I sometimes follow this brief description from http://klausler.com/cnotes.txt when reading type declarations

How to easily read a declaration from left to right:
— transform function argument types from inside out first
— move the base type to the end
— add outer parentheses if there’s an initial *
— change every (*…) to … ->
———— one -> for each *
———— move qualifiers, so * const becomes const ->

By: Miron Brezuleanu

Miron Brezuleanu — Sat, 19 Jul 2008 05:41:25 +0000

What about declarations that do not have a variable identifier? Example:
int f(int (*)());

This declares a function that return an int and takes a function pointer as argument. The function pointer is a nested declaration, and it doesn’t use a variable name. How do you figure out where to start when parsing the nested declaration?

By: eliben

eliben — Fri, 18 Jul 2008 15:55:17 +0000

Thanks for all the comments (here and on Proggit)- I’ve incorporated some of the information into the article.

Kia Kroas: why, pointing out typos *is* important. Thanks, fixed.

By: Kia Kroas

Kia Kroas — Fri, 18 Jul 2008 14:01:06 +0000

I’m not usually one to point out typos, but…in your second code box, you have inx instead of int.
“inx x[5];”
s/inx/int/

Otherwise, it was a nice, useful post.

By: bernz

bernz — Fri, 18 Jul 2008 13:53:14 +0000

Anyone who actually uses “char *(*(**foo [][8])())[]” must be smoking some pretty heavy stuff. Tip: When pretending you are a C parser, read type definitions from the inside, out.

By: miro

miro — Fri, 18 Jul 2008 11:39:38 +0000

Heh or just use a typedef
Granted it is complex (pascal has much nicer rules).

By: Pádraig Brady

Pádraig Brady — Fri, 18 Jul 2008 11:12:44 +0000

$ cdecl explain “char *(*(**foo [][8])())[];”
declare foo as array of array 8 of pointer to pointer to function returning pointer to array of pointer to char

By: Remko Tronçon

Remko Tronçon — Fri, 18 Jul 2008 09:46:42 +0000

I was about to say the same thing: If you want another good tutorial on reading C types, check out the excellent ‘Expert C Programming’ by Peter van der Linden.