A GCC param is wrong somewhere, for the Teensy2 (Atmel AVR)  target case. Compiles OK (C99 compatible) for Teensy3. Something differs in the C99 options for the two targets.

struct foo_t
{
    int me;
};
struct foo_t  thing =
{
    .me = 123;  // C99 standard's named initializer
};
 

I'll check. It may be that VM's arguments passed to GCC such as -std=  differ for Teensy 2 than Teensy 3, where the latter is correct.

In the Arduino IDE, when teensy 2 is chosen, the struct initializer by name per the C99 standard does not work. It does work when the teensy 3 is chosen (different command line). Same issue in VM. Of course, different versions of GCC are used for Teensy 2 and Teensy 3. The the choice of target core type has nothing to do with supporting struct init per C99.

I noted, in the GCC command line args, that Teensy 2 uses -std=c++0x  whereas Teensy 3 uses -std=gnu++0x. I don't know if that's relevant.

How does VM define the GCC command line it uses?

ah, that's why your comment implied "not a VM problem!"

Teensy is still on Arduino 1.0.5, as I read, because Arduino has yet to finalize a new library management methodology and implementation of such.

Sorry, I didn't explain that very well. 1.0.x is fine and I am in no position to comment on the default install of Teensy. It probably makes sense to stick with 1.0.

What I meant was that 1.5 is actually just a matter of making up the config files which we might find time to look at in a few months just for a bit of fun. The Visual Micro config supports adding another Teensy entry to the apps list with a different specification (Teensy 1.5). The underlying core can stay the same so the compiled program code remains the same. It's a job for someone who knows arduino and teensy config files.