fa1eef8bbe
Apart from bumping the toolchain Clang's and port's version, this commit completely overhauls the way LLVM toolchain is built. First, it gets rid of a complicated two-stage process of first compiling clang and compiler-rt builtins and then building libunwind, libc++abi, and libc++ -- it is possible to create a complete cross-compilation toolchain in a single CMake invocation with a modern LLVM. Moreover, the old method was inherently unsupported and subtly broken. Next, it utilizes full potential of the Stubs "framework". Now we are even able to compile Clang with -Wl,-z,defs which makes one of the patches obsolete and the whole installation less error-prone. Note that it comes at a cost of complicating the bootstrap process on a completely novel architecture but this hopefully won't happen often. Lastly, it fixes handling of the -no*lib* family of flags in the Serenity LLVM driver and correctly uses -nostartfiles in conjunction with stubs to make necessary CMake configure-time checks succeed. |
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| README.md | ||
Library stubs
This directory contains stubs for SerenityOS's LibC that are referenced from the LLVM runtime
libraries. These are needed by the linker in order to add the required DT_NEEDED entries and to
not emit errors regarding undefiend libc symbols. Additionally, it provides fake empty libunwind.so
and libc++.so for CMake configuration checks to succeed when bootstrapping the OS.
Do these need to be updated?
Most likely no but it depends. Either way, if you are reading this, you are probably qualified enough to figure out if a failing LLVM toolchain configuration or build is caused by an out-of-date LibC stub.
How to generate LibC stub?
First, you need to compile the LLVM toolchain and the SerenityOS's LibC. This will be a bit awkward
(see discussion at https://github.com/SerenityOS/serenity/pull/23960) until (unless) we solve the
dependency cycle between LibC and libunwind. Then, using the llvm-ifs tool,
Userland/Libraries/LibC/libc.so can be converted into a stripped-down stub form. To do that, run
the following command:
Toolchain/Local/clang/bin/llvm-ifs --output-elf=<path-to-stub> <path-to-original>
How to generate empty.so?
Simple, my friend:
touch empty.cpp
Toolchain/Local/clang/bin/clang++ --target={arch}-pc-serenity -nostdlib -shared empty.cpp -o empty.so
# And optionally,
Toolchain/Local/clang/bin/llvm-strip empty.so