This change implements a leftover task from #307211, namely passing
monorepoSrc to the different llvmPackages_13 package expressions. Before
this change, all packages llvmPackages_13 would be built from a
subdirectory of the full LLVM monorepo tree. After this change only the
relevant directories are made available at build time. This
- reduces the size of the source that needs to be made available to the
builder.
- prevents LLVM from sidestepping our instructions and including extra
sources from other directories it shouldn't.
Since LLVM 12 and 13 don't have the `cmake` directory at the top level,
the runCommand expressions filtering the source need to be adjusted, but
this causes no rebuild for any other LLVM version (ofborg should confirm
this).
The only problem encountered was in lld:
- We need to make the patch to the inclusion of libunwind headers
unconditional now. lld needs this on non-darwin as well. In the
full monorepo, LLVM_MAIN_SRC_DIR would be set correctly, so the
patch wasn't necessary.
- The substitute mechanism for LLVM 12 and 13 can't be unified yet since
LLVM 12 still uses a non monorepo build, so we come up with a
different LLVM_MAIN_SRC_DIR.
Change was tested by building the following expression on x86_64-linux.
with import ./. {};
builtins.removeAttrs llvmPackages_13 [ "lldb" "lldbPlugins" ]'
lld was also tested on aarch64-darwin.
cmake flags have a 'last flag wins' logic, so by appending to the end of
the flags it is possible to override any cmake flag.
It also ignores (and warns) if a flag is unused, so passing flags across
all packages should be safe if you want to target one package.
In combination with #320261, this PR allows consistently overriding all
packages within LLVM with additional cmake arguments. Consistency here
means for example 'if you override LLVM, then all dependencies on it are
also see the overridden LLVM in their input'. Consistency is hard to
achieve with the other obvious way of implementing this as a user: if
you use overrideAttrs then you have to write a big mess of override code
in order to override all dependents, and this can be very difficult in a
cross-compilation scenario using crossSystem and useLLVM, for example.
With this PR it is possible to write an overlay which overlays
`llvmPackages` with `llvmPackage.override { devExtraCmakeFlags = [ ... ]; }`,
and then the toolchain used with useLLVM in effect should respect
these flags.
This is useful in development for experimenting with the effect of
various flags, hence the chosen name `devCmakeFlags`.
This won't work out of the box without #341855 applied, which fixes
override passthrough.
See-Also: #320261, #341855
Signed-off-by: Peter Waller <p@pwaller.net>
If building clang under clang, don't pass -Wno-maybe-uninitialized;
this is a gcc-only warning and clang emits a diagnostic for every TU
about the unknown warning flag.
Signed-off-by: Peter Waller <p@pwaller.net>
Most Linux distributions are enabling this these days and it does
protect against real world vulnerabilities as demonstrated by
CVE-2018-16864 and CVE-2018-16865.
Fix#53753.
Information on llvm version support gleaned from
6609892a2d68e07da3e5092507a730
Information on gcc version support a lot harder to gather,
but both 32bit and 64bit arm do appear to be supported
based on the test suite.
Clang assumes that `libLTO.dylib` is located at `../lib` in the same
prefix as `clang`, but that’s not true in nixpkgs. `libLTO.dylib` is
actually located at `libllvm^lib/lib.libLTO.dylib`.
