Awesome

The XCC C Compiler

A C23(C2X) C compiler.

JIT

Just In Time Compilation demo

Setting up your environment - Install LLVM

The main driver is tests/main.cpp.

XCC provides makefiles in tests directory.

In Windows, a MSYS2 installation is recommended for convenience(you can download binarys without building from source!).

you can install LLVM via

# MSYS2
$ pacman -S mingw-w64-x86_64-llvm

Also you install gdb debug tool.

$ pacman -S mingw-w64-x86_64-gdb

In Debian and Ubuntu, https://apt.llvm.org/ provides llvm.sh can help you install LLVM and Clang.

Or use apt

sudo apt install llvm-15

Installing and Building

• Windows - MSYS2

Install LLD include headers and static library files(.a)

$ pacman -S mingw-w64-x86_64-lld

Build XCC (assume you MSYS2 is installed in C:/msys64)

$ clang++ main.cpp -DCC_HAS_LLD -fno-exceptions -fno-rtti -D_FILE_OFFSET_BITS=64 -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS C:/msys64/mingw64/lib/liblldWasm.a C:/msys64/mingw64/lib/liblldCOFF.a C:/msys64/mingw64/lib/liblldELF.a C:/msys64/mingw64/lib/liblldMachO.a C:/msys64/mingw64/lib/liblldMinGW.a C:/msys64/mingw64/lib/liblldCommon.a -lLLVM-15 -g C:/msys64/mingw64/bin/zlib1.dll

• Linux - GNU Make

Install LLD via apt/dpkg

$ sudo apt install liblld-15 liblld-15-dev

Or building from source

$ git clone https://github.com/llvm/llvm-project llvm-project
$ mkdir build
$ cd build
$ cmake -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_PROJECTS=lld -DCMAKE_INSTALL_PREFIX=/usr/local ../llvm-project/llvm
$ make install

Finally, build XCC with GNU make.

$ make
$ make main
$ make testLexer
$ make testCpp
$ make testParser
$ make testCodeGen
$ make all
$ make all -j

Features

Dump colored AST

cdecl syntax

Expressive diagnostics

Include stack information

Supports Windows, WSL, Linux ...

Fix-it Hints

_Complex, _Imaginary support.

• trigraphs

Support trigraphs(both two and three characters) in command line option -trigraphs.

Author

ianfun

• 015006@mst.hlis.hlc.edu.tw
• ianfun.github.io@gmail.com

References

• C23: https://open-std.org/JTC1/SC22/WG14/www/docs/n3054.pdf

Optimizations

• remove unused variables

  remove

  • global variables/functions which not used and have static linkage
  • local variables not used, if has initializer and the initializer has side-effects, replace with the initializer

• constant folding

  constant folding using LLVM's APInt, APFloat and llvm::Constant ...

Alignment

Alignment affects size of objects.

root [0] struct alignas(void*) bar {};
root [1] alignof(bar)
(unsigned long) 8
root [2] struct foo {};
root [3] alignof(foo)
(unsigned long) 1
root [4] sizeof(foo)
(unsigned long) 1
root [5] sizeof(bar)
(unsigned long) 8

Alignments must be power of 2 and must less or equal than the object's size.

root [1] struct alignas(2) bar { int a; };
ROOT_prompt_1:1:8: error: requested alignment is less than minimum alignment of 4 for type 'bar'
struct alignas(2) bar { int a; };

Memory Leaks

Use AddressSanitizer to detect memory leaks.

TODO List