What is "fnspec function type attribute"?

[Marc Glisse]

On Fri, 6 Jun 2014, FX wrote:

> In fortran/trans-decl.c, we have a comment above the code building function decls, saying:
>
>>    The SPEC parameter specifies the function argument and return type
>>    specification according to the fnspec function type attribute.  */
>
> I was away from GCC development for some time, so this is news to me. The syntax is not immediately clear, and neither a Google search nor a grep of the trunkΒ’s numerous .texi files reveals any information. IΒ’m creating new decls, what I am to do with it?

You can look at the 2 functions in gimple.c that use gimple_call_fnspec, 
and refer to tree-core.h for the meaning of EAF_*, etc. A string like 
"2x." means:
'2': the first letter is about the return, here we are returning the 
second argument
'x': the first argument is ignored
'.': not saying anything about the second argument.

-- 
Marc Glisse