Spotted some problems in the Driver's PrepareCommandsForSourcing while
helping a colleague track another problem.
1. One error case was not handled because there was no else clause.
Fixed by switching to llvm's early-out style instead of nested
`if (succes) { } else { }` cases. This keeps error handling close
to the actual error.
2. One call-site failed to call the clean-up function. I solved this
by simplifying the API. PrepareCommandsForSourcing no longer requires
the caller to provide a buffer for the pipe's file descriptors and to
call a separate clean-up function later. PrepareCommandsForSourcing
now ensures the file descriptors are handled before returning.
(The read end of the pipe is held open by the returned FILE * as
before.)
I also eliminated an unnecessary local, shorted the lifetime of another,
and tried to improve the comments.
I wrapped the call to open the pipe to get the `#ifdef`s out of the
mainline. I replaced the `close`/`_close` calls with a platform-neutral
helper from `llvm::sys` for the same reason. Per discussion on the
review, I'm leaving the `fdopen` call to use the spelling that Windows
has officially deprecated because it still works it avoids more `#ifdef`s.
Differential Revision: https://reviews.llvm.org/D60152
llvm-svn: 357626
ffa857c7a6