Now that the AOT-compiled code image is position-independent, there is
no further need for this distinction. In fact, it was harmful,
because we were still using runtime-generated thunks when we should
have been using the ones in the code image. This resulted in
EXC_BAD_ACCESS errors on non-jailbroken iOS devices.
It seems that the Apple iOS Simulator's stat implementation writes
beyond the end of the struct stat we pass it, which can clobber
unrelated parts of the stack. Perhaps this is due to some kind of
header/library mismatch, but I've been unable to track it down so far.
The workaround is to give it 8 words more than it should need, where 8
is a number I just made up and seems to work.
This avoids the requirement of putting the code image in a
section/segment which is both writable and executable, which is good
for security and avoids trouble with systems like iOS which disallow
such things.
The implementation relies on relative addressing such that the offset
of the desired address is fixed as a compile-time constant relative to
the start of the memory area of interest (e.g. the code image, heap
image, or thunk table). At runtime, the base pointer to the memory
area is retrieved from the thread structure and added to the offset to
compute the final address. Using the thread pointer allows us to
generate read-only, position-independent code while avoiding the use
of IP-relative addressing, which is not available on all
architectures.
This fixes a number of bugs concerning cross-architecture bootimage
builds involving diffent endianesses. There will be more work to do
before it works.
The File.length() method was returning a signed 32-bit value
on 32-bit Windows systems. This was causing an integer overflow
on file sizes greater than 2 GB. This appears to be caused by
the way Windows handles the STAT() function. This patch checks
whether the current platform is Windows then uses the Windows API
to get the correct file size and return it as a jlong.
Some apps and libraries may generate recoverable SEH exceptions on
Windows, in which cases we don't want to waste time and disk space
generating memory dumps.
This monster commit is the first step towards supporting
cross-architecture bootimage builds. The challenge is to build a heap
and code image for the target platform where the word size and
endianess may differ from those of the build architecture. That means
the memory layout of objects may differ due to alignment and size
differences, so we can't just copy objects into the heap image
unchanged; we must copy field by field, resizing values, reversing
endianess and shifting offsets as necessary.
This commit also removes POD (plain old data) type support from the
type generator because it added a lot of complication and little
value.
On Windows, some versions of Git automatically translate Unix line
endings to Windows line endings, which can break the build unless we
treat carriage returns as whitespace when parsing.
We now properly forward the errno value from the child when execvp()
fails, which the parent then uses to for the errno message as well as
including the failed command's name in the message.
