Version:           3.2.1 (using KDE KDE 3.4.1)
Installed from:    Gentoo Packages
Compiler:          3.4.3 
OS:                Linux

Example from the gcc info page:

Assume that `struct foo' and `structure' are declared as shown: 

      struct foo {int a; char b[2];} structure;


Here is an example of constructing a `struct foo' with a compound
literal:

      structure = ((struct foo) {x + y, 'a', 0});

The second line gets marked as an error, it is perfectly valid. Note that this is not an obscure extension, it is part of the ISO 99 standard.