The compiler doesn't handle response files at all. line-directive expands them.

I'm not sure what you're trying to do, either. You can't pass -primary-file with -Xfrontend. It has to go before the particular file that's the primary one.

The compiler doesn't handle response files at all. line-directive expands them.

That is what I suspected, and it's absolutely, obviously, the wrong design. This means any Windows users who don't want to use line-directive can't build swift code if the command line gets too long.

I'm not sure what you're trying to do, either.

I'm trying to do what Doug suggested.

You can't pass -primary-file with -Xfrontend. It has to go before the particular file that's the primary one.

It was going before the file that was the primary one. That doesn't make it exclusive with -Xfrontend, which preceded it—unless maybe there are rules behind the Swift command line that aren't clearly documented (at least, not where I can find them). It's all quite mysterious, so marking this invalid seems a bit... premature.

/cc erg (JIRA User) this is what I was talking about the other day.

-Xfrontend arguments are additional arguments to pass to the frontend; they have nothing to do with the non-Xfrontend arguments you pass.

Please don't try to play games with the driver.

Oh, and the compiler doesn't handle response files because the correct way to handle response files would be to accept any arguments, not just input files, and that's Difficult To Implement.

I have nothing against doing it, though.

llvm::cl::ExpandResponseFiles will probably help here.

Retitled to reflect the actual feature we can do. Inserting -primary-file via -Xfrontend just isn't ever going to be safe or supported.

Comment by Austin Belknap (JIRA)

Addressed this issue in PR: #15853. Still needs review.

Cherry-picked Austin's changes to the 4.2 branch: #17409