Rust no longer has support for JIT compilation, so it doesn't currently
require a PaX MPROTECT exception. The extended attributes are preferred
over modifying the binaries so it's not actually going to work on most
systems like this anyway.

If JIT compilation ends up being supported again, it should handle this
by *always* applying the exception via an extended attribute without
performing auto-detection of PaX on the host. The `paxctl` tool is only
necessary with the older method involving modifying the ELF binary.

If the compiler is built with --{llvm,jemalloc,libuv}-root, then the configure
script can skip updating these submodules.

Closes #14822

Closes #5563

This adds a new configure option, --jemalloc-root, which will specify a location
at which libjemalloc_pic.a must live. This library is then used for the build
triple as the jemalloc library to link.

Remove a warning  (./configure: 1140: [: unexpected operator) when built with --disable-manage-submodules

Signed-off-by: NOGINO Masanori <masanori.ogino@gmail.com>

I mostly tried to remain backwards compatible with old invocations of
the `configure` script; if you do not want to use `CC` et al., you
should not have to; you can keep using `--enable-clang` and/or
`--enable-ccache`.

The overall intention is to capture the following precedences for
guessing the C compiler:

 1. Value of `CC` at make invocation time.
 2. Value of `CC` at configure invocation time.
 3. Compiler inferred at configure invocation time (`gcc` or `clang`).

The strategy is to check (at `configure` time) if each of the
environment variables is set, and if so, save its value in a
corresponding `CFG_` variable (e.g. `CFG_CC`).

Then, in the makefiles, if `CC` is not set but `CFG_CC` is, then we
use the `CFG_CC` setting as `CC`.

Also, I fold the potential user-provided `CFLAGS` and `CXXFLAGS`
values into all of the per-platform `CFLAGS` and `CXXFLAGS` settings.
(This was opposed to adding `$(CFLAGS)` in an ad-hoc manner to various
parts of the mk files.)

Fix #13805.

----

Note that if you try to set the compiler to clang via the `CC` and
`CXX` environment variables, you will probably need to also set
`CXXFLAGS` to `--enable-libcpp` so that LLVM will be configured
properly.

----

Introduce CFG_USING_CLANG, which is distinguished from
CFG_ENABLE_CLANG because the former represents "we think we're using
clang, choose appropriate warning-control options" while the latter
represents "we asked configure (or the host required) that we attempt
to use clang, so check that we have an appropriate version of clang."

The main reason I added this is that I wanted to allow the user to
choose clang via setting the `CC` environment variable, but I did not
want that method of selection to get confused with the user passing
the `--enable-clang` option.

----

A digression: The `configure` script does not infer the compiler
setting if `CC` is set; but if `--enable-clang` was passed, then it
*does* still attempt to validate that the clang version is compatible.

Supporting this required revising `CLANG_VERSION` check to be robust
in face of user-provided `CC` value.

In particular, on Travis, the `CC` is set to `gcc` and so the natural
thing to do is to attempt to use `gcc` as the compiler, but Travis is
also passing `--enable-clang` to configure.  So, what is the right
answer in the face of these contradictory requests?

One approach would be to have `--enable-clang` supersede the setting
for `CC` (and instead just call whatever we inferred for `CFG_CLANG`).
That sounds maximally inflexible to me (pnkfelix): a developer
requesting a `CC` value probably wants it respected, and should be
able to set it to something else; it is harder for that developer to
hack our configure script to change its inferred path to clang.

A second approach would be to blindly use the `CC` value but keep
going through the clang version check when `--enable-clang` is turned
on.  But on Travis (a Linux host), the `gcc` invocation won't print a
clang version, so we would not get past the CLANG_VERSION check in
that context.

A third approach would be to never run the CLANG_VERSION check if `CC`
is explicitly set.  That is not a terrible idea; but if the user uses
`CC` to pass in a path to some other version of clang that they want
to test, probably should still send that through the `CLANG_VERSION`
check.

So in the end I (pnkfelix) took a fourth approach: do the
CLANG_VERSION check if `CC` is unset *or* if `CC` is set to a string
ending with `clang`.  This way setting `CC` to things like
`path/to/clang` or `ccache clang` will still go through the
CLANG_VERSION check, while setting `CC` to `gcc` or some unknown
compiler will skip the CLANG_VERSION check (regardless of whether the
user passed --enable-clang to `configure`).

----

Drive-by fixes:

* The call that sets `CFG_CLANG_VERSION` was quoting `"$CFG_CC"` in
  its invocation, but that does not play nicely with someone who sets
  `$CFG_CC` to e.g. `ccache clang`, since you do not want to intepret
  that whole string as a command.

  (On the other hand, a path with spaces might need the quoted
  invocation.  Not sure which one of these corner use-cases is more
  important to support.)

* Fix chk_cc error message to point user at `gcc` not `cc`.

This adds a `std::rt::heap` module with a nice allocator API. It's a
step towards fixing #13094 and is a starting point for working on a
generic allocator trait.

The revision used for the jemalloc submodule is the stable 3.6.0 release.

Closes #11807

Compile-fail tests for syntax extensions belong in this suite which has correct
dependencies on all artifacts rather than just the target artifacts.

Closes #13818

The goal of the snapshot bots is to produce binaries which can run in as many
locations as possible. Currently we build on Centos 6 for this reason, but with
LLVM's update to C++11, this reduces the number of platforms that we could
possibly run on.

This adds a --enable-llvm-static-stdcpp option to the ./configure script for
Rust which will enable building a librustc with a static dependence on
libstdc++. This normally isn't necessary, but this option can be used on the
snapshot builders in order to continue to make binaries which should be able to
run in as many locations as possible.

OSX often has a more recent version of clang than it does for GCC. When an older
version of gcc is detected on OSX, the --enable-clang flag is implicitly
enabled.

When clang is enabled, also pass through --enable-libcpp to LLVM's configure
command line to help it pick up the most recent c++ runtime library. This also
changes the mklldeps.py script to pick up on whether LLVM was linked against
stdc++ or c++ based on the --cxxflags that llvm-config prints.

In an ongoing attempt to update LLVM, the bots need to update their C compilers
to something that supports c++11 (LLVM recently switched). The OSX bots are
running Lion (10.7), which only supports up to gcc 4.2 and clang 3.2. Apparently
the libstdc++ is too old (even on the most updated command line tools) for LLVM,
but using libc++ instead appears to work just fine.

This comes with a number of fixes to be compatible with upstream LLVM:

* Previously all monomorphizations of "mem::size_of()" would receive the same
  symbol. In the past LLVM would silently rename duplicated symbols, but it
  appears to now be dropping the duplicate symbols and functions now. The symbol
  names of monomorphized functions are now no longer solely based on the type of
  the function, but rather the type and the unique hash for the
  monomorphization.

* Split stacks are no longer a global feature controlled by a flag in LLVM.
  Instead, they are opt-in on a per-function basis through a function attribute.
  The rust #[no_split_stack] attribute will disable this, otherwise all
  functions have #[split_stack] attached to them.

* The compare and swap instruction now takes two atomic orderings, one for the
  successful case and one for the failure case. LLVM internally has an
  implementation of calculating the appropriate failure ordering given a
  particular success ordering (previously only a success ordering was
  specified), and I copied that into the intrinsic translation so the failure
  ordering isn't supplied on a source level for now.

* Minor tweaks to LLVM's API in terms of debuginfo, naming, c++11 conventions,
  etc.

The previous regex was a bit to strict, rejecting versions such as 3.4.1 which
is apparently the version which travis is currently installing, causing all
travis builds to fail.

MSYS2 supports `MINGW64` system for 64-bit environment. It sets
`MSYSTEM=MINGW64` environment variable, which changes output of
`uname -s` thus affects `configure` behavior.

This patch adds `MINGW64*` support for `configure`.

Another sanity check. Can be disabled in `install.sh` via `--disable-verify`
and `configure` with `--disable-verify-install`.

Trying to reduce the complexity of installation

`prep.js` outputs its own HTML directives, which `pandoc` cannot
recognize when converting the document into LaTeX (this is why the
PDF docs have never been highlighted as of now).

Note that if we were to add the `.rust` class to snippets, we could
probably use pandoc's native highlighting capatibilities i.e. Kate.

std::condition was removed in 454882dc
but there are still links to the guide. Removing them.

This is the current head of LLVM, and we can indeed build with 3.5

This is the current head of LLVM, and we can indeed build with 3.5

This way of doing snapshots hasn't been used since 2011.

This upgrade brings commit by @EddyB to help optimizations of virtual calls in
a few places (https://github.com/llvm-mirror/llvm/commit/6d2bd95) as well as a
commit by @c-a to *greatly* improve the runtime of the optimization passes
(https://github.com/rust-lang/llvm/pull/3).

Nice work to these guys!

By default, the compiler and libraries are all still built with rpaths, but this
can be opted out of with --disable-rpath to ./configure or --no-rpath to rustc.

cc #5219

We'll use this when building snapshots so we can upgrade freely, but all
compilers will inject a version by default.