The goal here is to be able to construct a build of the runtimes
directly in Bazel, or by emitting `BUILD` files, or by emitting into C++
code and using that on-demand. For that, we want a single source of
truth, and that source in Starlark.
This should also make the information more generally useful, and so I'm
moving as much as I can into the LLVM Bazel build. Apologies as that
makes the diffs extra annoying.
I do plan on upstreaming the Bazel parts of this, but would like to get
everything working in Carbon and stabilized first.
While here, I've also made a change suggested for the future in the
initial review by lifting the C++ template out of a string literal in
the `.bzl` file, and into an actual separate C++ file.
This only moves libc++, libc++abi, and libunwind. I want to get those
three working end-to-end before I work on the builtins or `crtbegin` and
`crtend`, as those have a bunch of additional complexity.
This also only uses the info in the C++ on-demand build. It seemed like
a reasonable increment to start code review, and my plan is to work on
other build strategies in a follow-up PR. If that doesn't work, let me
know and I'll come back once I have at least a second use of the info
here.
This let's you point Bazel at an installed toolchain or download one of
our release archives. When you do, it will configure itself as a C++
Bazel toolchain. This toolchain works reasonably well, but doesn't cache
the C++ runtimes, and so linking is inefficient. The next step will be
to pivot the runtimes from the implicitly on-demand (which can't cache
when using a sandboxed build system like Bazel) to _explicit_ on-demand
runtimes directly with Bazel support.
I've included an example Bazel project that uses this and provides a
bunch of documentation and an example script that should let folks try
this out easily.
---------
Co-authored-by: Geoff Romer <gromer@google.com>
Co-authored-by: David Blaikie <dblaikie@gmail.com>
This requires re-working our config features to be usable in
feature-level `requires` clauses in addition to `with_feature_set` by
always including all of the features, but controlling whether the
features are enabled or disabled based on the target.
This is a little more verbose in the config features, but lets us use
them more widely and is a bit more principled.
This lets us use a single undconditional feature for linking with flag
sets that are enabled based on the underlying OS. While here, tidy up
the feature names a bit.
The diff here may look really bad without aggressive whitespace
ignoring, but none of the contents of the two flag sets changed --
they've just be indented more and placed into a single list.
Now the CPU flags feature can be unconditionally added as part of the
optimization features and another of the conditions in the main
configuration goes away.
The failure to pass these to links was probably harmless, but it's
better to include it there as well.
This removes another chunk of platform-specific feature construction and
simplifies the code further.
Also removes a now-stale comment about adding more platform-specific
features.
---------
Co-authored-by: Geoff Romer <gromer@google.com>
This PR merges the OS-specific Clang flags into the main Clang flags
features using feature-based constraints instead of separate features
conditionally added. Similarly for libc++. This also move flags to more
correctly live in the Clang flag set vs. the libc++ flag set as some of
these flags were specific to using libc++.
To make this change, the libc++ feature needs to be computed rather than
being fixed, as we need to add search paths based on the installed
location of LLVM and Clang.
All of this only works when the OS-config flags work. The earlier PR
adding these had a bug -- _none_ of the OS features would ever be
enabled. This didn't result in a problem as the initial use was only to
_disable_ flags on the wrong OS. Now that we're enabling flags, we have
to get it right by marking all of these as `enabled`.
This leaves behind project-specific features such as the system header
management of our dependencies and the fancy cache management string.
No expected changes here, but yet another slightly different order of
flags.
This introduces the first pieces of a cleaner way to configure toolchain
components on target dimensions: dedicated features for those target
dimensions.
With that, we extract a `libcxx_feature` that can always be present but
disables its flags on unsupported targets.
With `-stdlib` in its own feature, move `-std=c++20` to not require
a variable but directly live in the flags.
This should enable us to extract the largest remaining feature into its
own file cleanly by removing dynamic configuration of it, along with
libcxx.
Further refactoring of target-specific logic will follow in its
footsteps.
This brings some fixes:
- The handling of `zlib` and `zstd` are much cleaner
- Three of our patches are no longer needed
This also includes the fixes from #6562
It also moves us from `zlib` to `zlib-ng` which is a much better basis
for what we want, and likely makes our toolchain faster when generating
debug info at least.
It fixes another API change in terms of which headers provide the
`createInvocation` we use.
Lastly, it cleans up the deps test to correctly recognize the wrappers
for `zlib-ng` and `zstd`, as well as improving the documentation for why
we allow dependencies on them.
This moves the simplest parts of the toolchain config into separate
files. These parts are either unparameterized or trivially parameterized
and so easily extracted from the main file.
I tried to minimize the interesting edits here, but wasn't _completely_
successful I'm afraid. I'll try to describe them.
First, all of the interesting content of the new files is copied and
re-indented, no interesting edits were done.
The main file sees some more significant edits in order to realize this
refactoring:
- Extract the feature array building to a helper method.
- Collapse some extraneous features as there was no where to extract
them.
- Restructure how the array itself is built to support building it using
array fragments from the various files.
The only interesting semantic change I'm aware of here is that this
somewhat changes the order of command line flags in compiles and links.
The previous order was "fine", but not especially logical. I've tried to
more logically have features that should "override" or are "more
specific" come later here. However, that results in a slightly different
ordering. None of the current features had any flags that overlap, so
this should have no behavior change other than the changed flag order.
This is only the first step, however. There remain complex features in
the main configuration that I want to move out. However, to make those
moves simple requires some significant changes to how these remaining
features work and so I wanted to break them out. I've tried to leave
TODOs that can help as breadcrumbs on the parts of this refactoring that
aren't yet complete.
The comments also are mostly what we already had. I'm happy to try and
add some, but not sure how much I can cover as there is a _lot_ of code
here that I'm just moving around. Please let me know if there are
particularly places that would benefit from comments.
---------
Co-authored-by: Geoff Romer <gromer@google.com>
These checks include a full check that a red-black tree satisfies its
invariants on every erase. This leads to
`llvm::DWARFDebugAranges::construct` becoming quadratic in the number of
debug symbols in the binary, which means that in `-c dbg`, symbolization
of backtraces is astronomically slow, and in practice never completes.
(I left it for over 12 hours and it did not finish.)
Reduce the libc++ hardening mode from *debug* to *extensive* to turn off
the checks that have unbounded performance impact.
Previously, we used the FHS "prefix" concept as the basis of the
install, but this makes it hard to integrate an installed toolchain with
Bazel (or similar) build system where it wants the "root" of the
toolchain to have some specific files (`MODULES.bazel` or
`BUILD.bazel`), and cannot reference anything outside that directory
tree.
An easy solution is to make the `lib/carbon` directory the root of the
install and never walking up from it. Then we simply have a `bin/carbon`
symlink to the busybox that is useful for getting the command into the
PATH, but isn't used for anything else. The FHS-constrained install
paths surround a root we fully control the layout and files within.
While initially motivated by trying to make a single toolchain structure
that works both for installation and for Bazel, it actually makes the
paths we end up using in the toolchain much simpler. We no longer have
awkward `.../lib/carbon/../../lib/carbon/...` sequences in the toolchain
which is cleaner and even a (trivial) efficiency gain.
As I was doing this I noticed several out-of-date comments that I tried
to fix, and I tried to improve some code reuse rather than re-computing
paths.
---------
Co-authored-by: Geoff Romer <gromer@google.com>
Also consolidate on using `//bazel/cc_rules:defs.bzl` where appropriate.
Also update a couple of Bazel modules deps of `@rules_cc` to the latest
versions.
Sadly, the formatter for starlark doesn't fully canonicalize the
formatting -- new lines and trailing `,`s can influence this formatting.
I've tried to pick a canonical format for these:
- Collapse as many balanced delimited sequences into a single line
without exceeding 80-columns.
- Collapse as many single comma-separated elements in a delimited region
into single lines with multiple opening constructs and single lines with
multiple closing constructs, reducing indentation and lines that consist
of only an opening delimited construct.
Generally, my goal with these heuristics was to minimize the number of
lines and indentation without creating irregularities, formatting
incompatible with `buildifier`, or egregiously long lines.
I've also tried to lexicographically sort named parameters where there
isn't any important ordering and currently there was a mixture just so
that we have a canonical ordering.
I've removed some redundant parentheses around arrays.
And lastly, I've reformatted some quite long lines to follow a pattern
that fits easily in 80-columns.
This shouldn't result in any behavior changes, just trying to tidy
things up here before making some more significant edits to refactor
this into composable logic instead of a single monolith.
If others have suggestions for different formatting, I'm happy to
change. I don't have any strong feelings about the formatting here, I
just wanted it to be consistent.
This enables on-demand building of runtimes by default, and enables
their header files for all of the Clang invocations. This also switches
the default flags to use the LLVM-provided runtimes (compiler-rt,
libunwind, and libcxx).
This also switches even `llvm_symlinks_test` to use the Bazel prebuilt
runtimes, which requires having a way to pass a Carbon flag even when
invoking the busybox as `clang` or `clang++`. This uses the pattern that
has worked for other Clang wrappers of spelling flags:
`-X<tool-name>=--flag=value`
Last but not least, this updates the Carbon Bazel rules to use our
installed and the Bazel prebuilt runtimes. With that, we make the C++
interop hello-world be enabled by default as this should pass reliably
on both Linux and macOS now.
This builds on the previous work to flesh out more on-demand runtimes
building. It adds building of the `libc++.a` archive runtime.
A number of changes are required for this to work:
- The runtimes build infrastructure needs to support building sources
from multiple parts of LLVM rather than a single part. We do this by
lifting the root of the runtimes source paths up a level to a common
runtimes tree, and installing the runtimes sources below this
directory.
- Both libc++ and libc++abi runtimes sources need to be installed, and
we even need to install some interesting parts of llvm-libc that are
used in the build of libc++.
- We need to generate the site configuration header file for libc++ from
the CMake template. This includes both setting up a set of
platform-independent defines and introducing some basic Bazel support
for processing the CMake template itself.
Doing all of this also exposed some missing features and limitations of
the runtimes building infrastructure that are addressed here.
One note is that all of this just adds libc++ to the explicit
`build-runtimes` command for testing. It doesn't yet trigger
automatically building these prior to linking, or configuring any of the
other subcommands to automatically use these runtimes. All of that will
come in follow-up PRs.
Also, this makes the `clang_runtimes_test` ... _very_ slow in our
default build configuration. Compiling libc++, even with many threads on
a large Linux server requires up to 50 seconds. I'm open to any
suggestions on how to handle this, including disabling the test in
non-optimized builds. I have some ideas to speed this up, but
fundamentally building libc++ is... not cheap.
I did look at some of the existing Bazel tools to process the CMake
template, but they all seemed significantly more complex than what we
need and didn't have broad adoption. Given that, it seemed slightly
better to just roll our own given the simple format.
Two of the new LLVM patch are currently under review upstream and so
hopefully temporary:
- https://github.com/llvm/llvm-project/pull/169155
- https://github.com/llvm/llvm-project/pull/169292
This test started failing with #6405, but it wasn't caught by our PR
testing or the merge queue as the test didn't _appear_ to be impacted by
the change (I think).
When run explicitly, as the post-commit actions do, it started failing
because of the new dependency edge.
This is the first real step towards building libc++ itself, and fleshes
out both the core runtimes management logic and the archive-based
runtimes logic for a quite simple runtime.
Nothing here causes us to _use_ libunwind, and in fact this doesn't
include even the "on-demand" aspect of building `libunwind`. Instead,
this just wires it up to the explicit `build-runtimes` subcommand for
simple testing. The full integration along side the target directory is
future work.
Most inputs are matched against the current regex. An input that starts
and ends with `/` sets a new regex instead. EOF terminates the program.
---------
Co-authored-by: josh11b <15258583+josh11b@users.noreply.github.com>
This removes the need for a patch and improves on the quality of the
rules significantly. A follow-up PR will use this to apply a number of
fixes to how we build the runtimes.
This is the first step to having Clang's runtime libraries fully
available for the Carbon toolchain. This PR focuses on the lowest level
runtimes, the CRT files and the builtins library.
The goal is to intercept Clang runs where it needs these
target-dependent pieces to be available, and build them on demand using
our Clang-running infrastructure. This avoids most of the subprocess
overhead, but there is still some due to missing features in Clang.
This requires exporting the sources for these runtimes from the Bazel
build, and installing them in our target-independent resource directory.
We then build a simplified "build" of these sources within the
`ClangRunner` itself to produce the specific artifacts and layout
expected by Clang.
It also required fixing our use of Clang on macOS to have a default
system root in order to successfully compile or link.
It also required cleaning up how the `ClangRunner` used target
information more generally -- instead of taking the target as
a constructor parameter, it manages its target internally and relies on
the Clang target-specifying command line flags.
I looked at whether we could split this into another layer separate from
the `ClangRunner`, but that proved frustratingly difficult to manage.
While we support building these on-demand as part of a detected link,
that doesn't seem feasible as we don't have the necessary separation
between compilation runs of Clang and link runs of Clang. However,
I have tried to factor the internals to provide as clear of separation
as I could across these.
I have also created a stand-alone subcommand to directly build the
runtimes which allows for easy testing. It also supports building them
into a specific directory, and that directory can in turn be passed to
a Clang invocation. This is designed to work both at the API level with
`ClangRunner` and at the subcommand level.
Currently, the only part of the commandline that is detected and
forwarded to the runtimes build is the target. Eventually, the plan is
to expand this so that we can build a maximally tailored set of runtimes
for a given compilation.
The other big TODO here is to actually implement caching storage of
these runtimes so they aren't built on every execution. Right now, this
uses a somewhat hack-y build of a temporary directory, but this isn't
expected to be suitable long-term. Building these runtimes on *every*
link makes those commands take approximately 15 seconds with an ASan
build like our default development build, and just over 2 seconds in an
optimized build. Because of this, I've kept all of this disabled by
default for now. The goal is that once caching and some other
improvements land, we can enable this by default.
---------
Co-authored-by: Jon Ross-Perkins <jperkins@google.com>
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
Stop using the clang tooling library to build an ASTUnit; that library
is set up to process clang frontend arguments, assuming that something
has already built frontend arguments from the compiler arguments. It is
also too encapsulated and doesn't let us inspect and modify the compiler
invocation before it's executed.
Instead, build the AST unit directly in two phases:
* FIrst, take a list of clang driver arguments and convert them into a
list of compiler arguments, using `clang::createInvocation`. Internally,
this uses the clang driver to build a frontend invocation, including
building system-specific include paths as needed.
* Then, directly build an ASTUnit from this compiler invocation.
I've factored this so that we can split out the `createInvocation` step,
with the intention that we may want to move it out of check and into the
carbon driver with the rest of the driver-level argument handling, and
we may want to customize some of the clang options before we invoke the
clang frontend with that set of options.
In order to make the invocation reusable, it no longer depends on the
name of the carbon file importing the C++ code. In place of synthesizing
a header file name as `<foo.carbon>.generated.cpp_imports.h`, we now
insert line marker directives into the generated header so that errors
in that header cause Clang to point a diagnostic back at the Carbon
source file itself. This results in a minor improvement in the
diagnostic output: we no longer refer to a nonexistent generated file.
But the snippet still contains text that doesn't match the source code,
so it remains imperfect.
---------
Co-authored-by: Chandler Carruth <chandlerc@gmail.com>
This is based on #5664 because it's fixing an issue which `DEBUG` would
catch. That's also why I'm switching to `DEBUG` from `EXTENSIVE`; I
think we should be okay with the performance cost in `file_test`, which
is probably our main concern.
Note digging into this also got me to notice that the flags weren't
actually enabled; this is fixing the define names.
---------
Co-authored-by: Dana Jansens <danakj@orodu.net>
This avoids reallocating the backing buffer in ValueStore so that
references into the ValueStore are never invalidated when adding new
values. This works especially well since we never delete values from a
ValueStore.
The strategy used is to allocate chunks of a fixed size, and inserting
into each chunk until it is full before allocating the next. The
ValueStore starts with an initial allocated chunk in all cases, so that
there is only a single indirection for adding and accessing values from
this chunk. After it's full, additional chunks are allocated in a
vector, so two indirections are required to add or access values in
these chunks.
This obviates the need for
https://github.com/carbon-language/carbon-lang/pull/5529 as we no longer
need to worry about holding pointers into a ValueStore.
We introduce a Flatten operation for ranges. It flattens a "range over
ranges over Ts" down to a "range over Ts". This allows us to make an
range over the values in the ValueStore from a range over the chunks in
the ValueStore. See
https://doc.rust-lang.org/stable/std/iter/trait.Iterator.html#method.flatten
for inspiration for this name choice. Flatten is used in one other case
where we were writing two levels of for loops to do the same thing.
The `array_ref()` accessor is changed to `values()` and its now a range
(typed as a `ValueStoreRange`) over all values as references (like
ArrayRef was, but without random access).
As pointers to a ValueStore can no longer be invalidated, we remove the
ASAN poisoning feature and support from ValueStore.
This may cause a regression in our compile benchmark of up to 5%, though
that is close to or within the noise of the benchmark. We can look at
ways to optimize things further in the future. Perhaps by tuning the
chunk size further, or by making later chunks larger than earlier
chunks, or other strategies.
This reverts commit 1889ee3904.
We have identified that this is causing ODR violations, because the
`fuzzer` feature is being added `cc_fuzz_test` targets, and thus any
includes they make, but not to the rest of the build. Any include that
is seen from both places has ODR violations if it branches on
FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION.
We need to apply fuzzer globally when building fuzz targets somehow, or
not set different defines in fuzzer.
The `FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION` flag is a standard flag
proposed by LibFuzzer that is meant to inform compiled code that it is
being built for fuzzing, as described here:
https://llvm.org/docs/LibFuzzer.html#fuzzer-friendly-build-mode
We add the flag to our `fuzzing` feature/config, and enable DCHECKs when
under fuzzing so that we can catch bugs that currently are caught on the
other side of DCHECK, even if they don't cause ASAN to trap a read/write
beyond the capacity of a value store.
With this enabled, entities that live in value stores are poisoned
whenever any action is taken that might invalidate pointers and
references to those options -- in particular, adding another item to
that value store, or attempting to load any entity from an import IR.
Subsequent uses of those pointers or references then trigger an ASan
failure.
This detects latent bugs where the pointer or reference to the entity
would become stale if we got unlucky about when the value store
reallocates, even in cases where the reallocation didn't actually
happen.
This is not enabled by default: it finds a lot of latent bugs, so our
tests don't pass with this option. This PR also includes fixes for a few
of those bugs.
---------
Co-authored-by: Chandler Carruth <chandlerc@gmail.com>
Co-authored-by: Carbon Infra Bot <carbon-external-infra@google.com>
#5445 updates to bazel 8.2.1, this does more updates (including to
buildifier, which does autofixes like the `sh_test` loads in the other
PR).
Note I'm using the latest available clang-format wheel. That's not
really something I expect people to have installed, but should mostly be
consistent. I'm specifically skipping clang-format 18 because it had
some broad regressions, and 19 got really confused by a `requires` on a
trailing return. Using the latest seemed probably okay since most people
won't see the difference. Do note that trailing returns in macros,
https://github.com/llvm/llvm-project/issues/47664, seems to be cropping
up again as an issue.
- Updates incompatible flags.
- `rules_flex` is no longer used, so enable its flag.
- Fixes `sh_test` deps for
`--incompatible_disable_autoloads_in_main_repo`
- Broadens the exception for `rules_cc` and `bazel_tools` due to changes
to runfiles deps; trying to avoid minutiae that shouldn't affect the
decision.
Ran into this trying to debug #5428
Before:
```
lex.cpp:793:21: runtime error: null pointer passed as argument 1, which is declared to never be null
string.h:90:51: note: nonnull attribute specified here
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior lex.cpp:793:21
```
After:
```
lex.cpp:793:21: runtime error: null pointer passed as argument 1, which is declared to never be null
string.h:90:51: note: nonnull attribute specified here
#0 0x5572db22a680 in Carbon::Lex::Lexer::MakeLines(llvm::StringRef) /proc/self/cwd/toolchain/lex/lex.cpp:793:14
#1 0x5572db227ee4 in Lex /proc/self/cwd/toolchain/lex/lex.cpp:738:3
(etc)
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior lex.cpp:793:21
```
Interestingly, even though this is labelled as UB, it's using the
ASAN_SYMBOLIZER_PATH (specifically not LLVM_SYMBOLIZER_PATH). But
canonically UBSAN_SYMBOLIZER_PATH may also be used per
https://github.com/llvm/llvm-project/blob/main/compiler-rt/lib/ubsan/ubsan_flags.cpp#L53,
so I'm adding it to the list out of an excess of caution.
Also doing some small related cleanup:
- Removing `ASAN_SYMBOLIZER_PATH` from `--test_env` because it should
now be getting overridden by these settings (also was a little
inconsistent in that `LLVM_SYMBOLIZER_PATH` was not included).
- Improving the environment construction and documentation.
- Add pkg rules to the search, specifically so that we can pull the full
release tar instead of the busybox binary.
- Shift the tree_sitter exclusion to the script, so that it's easier to
use the script.
- tcmalloc_if_linux_opt isn't really interesting (it's referenced by
.bazelrc).
- Misc tiny changes to the query, just to simplify it.
Rules executed by bazel don't necessarily have the right environment to
find the symbolizer, which was the intent of `cc_env` setting
`LLVM_SYMBOLIZER_PATH`. So far, this has kind of been a case-by-case
fix, but every so often I'm trying to debug a crash in a test that
doesn't provide it. Rather continuing down this route, instead add
drop-in wrappers for cc rules so that it's hard to forget.
Note `bazel/cc_rules` is intended to mirror `bazel/carbon_rules` and
`bazel/cc_toolchains`, rather than `@rules_cc`.
AFAICT there isn't a great way to add this as a default for the `bazel
run` environment. It's not typically going to be set on its own,
forwarding `$PATH` would be too broad, and the [action
`env_sets`](https://bazel.build/docs/cc-toolchain-config-reference#using-action-config)
I think are not quite what we need (I think those don't include output
execution, only compilation).
Chandler Carruth
Justin Horvitz
Richard Smith
