[cfe-dev] FunctionDecls by typedef crash the C++ front-end

Chris Lattner clattner at apple.com
Thu Oct 23 22:33:23 PDT 2008

On Oct 23, 2008, at 6:37 PM, Argiris Kirtzidis wrote:

> e.g:
> typedef void fn(int);
> fn f;
> There are no ParmVarDecls created for the 'f' FunctionDecl, and I  
> assume
> this is intended to save space.
> This crashes the C++ front-end when trying to use the ParmVarDecls
> (mostly for handling default args).
> In C there is no problem since ParmVarDecls are used only for
> definitions, otherwise FunctionTypeProto is used

Two options here.  The best is probably for the C++ front-end to  
create the parm var decls in this case, to be consistent with "void  
f(int);".  The typedef shouldn't affect the AST generated other than  
the pretty type.

Long term, I'd love to get rid of parm var decls in the common case.   
They are needed for stuff like this in C:

void f(int i, int x[i*42]);

etc.  However, this is obviously not the common case, and most clients  
don't care about parmvardecls in function prototypes.  Considering  
that tons of headers have lots of function prototypes, I think this  
would be a big win.  This isn't a particularly high priority though,


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