Make this stuff a bit easier to maintain by using the
root level variables to build up the Toolchain paths.
Also leave a note for future editors of BuildIt.sh to
give them warning about the other changes they'll need
to make.
This enables building usermode programs with exception handling. It also
builds a libstdc++ without exception support for the kernel.
This is necessary because the libstdc++ that gets built is different
when exceptions are enabled. Using the same library binary would
require extensive stubs for exception-related functionality in the
kernel.
GCC determines whether the system's <limits.h> header is usable
and installs a different version of its own <limits.h> header
depending on whether the system header file exists.
If the system header is missing GCC's <limits.h> header does not
include the system header via #include_next.
For this to work we need to install LibC's headers before
attempting to build GCC.
Also, re-running BuildIt.sh "hides" this problem because at that
point the sysroot directory also already has a <limits.h> header
file from the previous build.
realpath(1) is specific to coreutils and its behavior can be had
with readlink -f
Create the Toolchain Build directory if it doesn't exist before
calling readlink, since realpath(3) on at least OpenBSD will error
on a non-existent path
* Add SERENITY_ARCH option to CMake for selecting the target toolchain
* Port all build scripts but continue to use i686
* Update GitHub Actions cache to include BuildIt.sh
A good number of contributors use macOS. However, we have a bit of
a tendency of breaking the macOS build without realising it.
Luckily, GitHub Actions does actually supply macOS environments,
so let's use it.
This is necessary because cache reusability will be determined by Github Actions.
Note that we only cache if explicitly asked to do so,
which only happens on Github Actions.
When libstdc++ was added in 4977fd22b8, just calling
'make install' was the easiest way to install the headers. And the headers are all
that is needed for libstdc++ to determine the ABI. Since then, BuildIt.sh was
rewritten again and again, and somehow everyone just silently assumed that
libstdc++ also depends on libc.a and libm.a, because surely it does?
Turns out, it doesn't! This massively reduces the dependencies of libstdc++,
hopefully meaning that the Toolchain doesn't need to be rebuilt so often on Travis.
Furthermore, the old method of trying to determine the dependency tree with
bash/grep/etc. has finally broken anyways:
https://travis-ci.com/github/SerenityOS/serenity/builds/179805569#L567
In summary, this should eliminate most of the Toolchain rebuilds on Travis,
and therefore make Travis build blazingly fast! :^)
./configure generates about 3500 lines in a few seconds. Noone will ever read
those lines and they make loading the Travis webpage slower. And if there is
ever a problem, it will be because the Travis base image changed (which happens
only rarely) in a way that interferes with compiling gcc (which is incredibly
unlikely), or we update gcc (which happens very rarely) and gcc doesn't like
the Travis iamge (which again is incredibly unlikely). In all of these cases,
finding the culprit will be self-evident.
Empirically, every single push or PR has to download *and then upload*
about 3.6 GiB of "cache stuff", which takes up about 400 seconds:
https://travis-ci.com/github/SerenityOS/serenity/builds/177500795
On every single push/PR! No matter what!
Those 3.6 GB consist of:
- 3.2 GB Toolchain cache (around 260 MB per compressed item)
- 0.4 GB ccache, but is capped at 0.5 GB: https://travis-ci.com/github/BenWiederhake/serenity/builds/177528549
- (And 200 KB for some weird debian package? Dunno.)
Investigating in the size, the Toolchain consists mostly of *DEBUG SYMBOLS IN
THE COMPILER BINARIES* which comically misses the point. If we ever run into
compiler crashes, any stacktrace would be lost anyway as soon as the Travis VM
shuts down. Furthermore, Travis will only ever compile Serenity itself, and
Serenity forbids C in it's Contribution Guidelines. That's another 20 MB we
don't need to cache.
Stripping the binaries and deleting the C compiler reduces the uncompressed size
from 1200 MB down to 220 MB. The compressed size gets reduced from 260 MB to 70MB.
That's a reduction of 73%.
It'll take a while until the 'old' toolchains get deleted.
I guess it'll take less than a week.
From that point onward, the Travis cache will be 1.2 GB, consisting of:
- 0.7 GB Toolchain cache
- 0.5 GB ccache
- (And that weird 200 KB deb file)
If network speeds are linear, then this should reduce the "cache network
overhead time" from about 400 seconds to about 120 seconds.
tl;dr: Strip unnecessary debug infos, delete an unused files, and speed
everything up by two minutes. (Both Toolchain cache hits and Toolchain rebuilds!)
This change allows users to use CMAKE_GENERATOR=Ninja ./BuildIt.sh
BuildIt.sh assumes the default cmake generator is Make. However,
the user may specify CMAKE_GENERATOR=Ninja, for example, to set the
default generator. Therefore, instead of calling make to build the
LibC target we should call cmake --build to use the correct generated
files.
We can do away with that shenanigans now that libstdc++ is gone.
Also, simplify the toolchain dependency hash calculation to only depend
on the toolchain build script(s) and the Patches files we use to modify
the toolchain itself.
This is __cxa_guard_acquire, __cxa_guard_release, and __cxa_guard_abort.
We put these symbols in a 'fake' libstdc++ to trick gcc into thinking it
has libstdc++. These symbols are necessary for C++ programs and not C
programs, so, seems file. There's no way to tell gcc that, for example,
the standard lib it should use is libc++ or libc. So, this is what we
have for now.
When threaded code enters a block that is trying to call the constructor
for a block-scope static, the compiler will emit calls to these methods
to handle the "call_once" nature of block-scope statics.
The compiler creates a 64-bit guard variable, which it checks the first
byte of to determine if the variable should be intialized or not.
If the compiler-generated code reads that byte as a 0, it will call
__cxa_guard_acquire to try and be the thread to call the constructor for
the static variable. If the first byte is 1, it will assume that the
variable's constructor was called, and go on to access it.
__cxa_guard_acquire uses one of the 7 implementation defined bytes of
the guard variable as an atomic 8 bit variable. To control a state
machine that lets each entering thread know if they gained
'initialization rights', someone is working on the varaible, someone is
working on the varaible and there's at least one thread waiting for it
to be intialized, or if the variable was initialized and it's time to
access it. We only store a 1 to the byte the compiler looks at in
__cxa_guard_release, and use a futex to handle waiting.
In order to remove libstdc++ completely, we need to give up on their
implementation of abi::__cxa_demangle. The demangler logic will actually
have to be quite complex, and included in both the kernel and userspace.
A definite fixme for the future, to parse the mangled names into real
deal names.
Back in 36ba0a35ee I thought that Travis would
automagically delete theoldest files. Apparently it does not.
Note that no dummy changes are needed, because BuildIt.sh lists itself
as a dependency for the Toolchain. Hooray for something that works!
The toolchain builds just fine without the git repository (tested on
windows and linux). We can skip setting up the repo and apply the
patches directly when we aren't working on the toolchain itself. A
flag `--dev` has been added for cases when git repo is needed. Without
the flag, regular patch is applied. This significantly improves build
times for first time builds.
