ATLAS — C compiler for x86-64 Windows

Capabilities

Preprocessor Full macro expansion — object-like, function-like, variadic (__VA_ARGS__). Token pasting (##) and stringification (#). Recursive #include with cycle detection. #ifdef/#if/#elif. #pragma pack push/pop. Automatic discovery of Windows SDK and MSVC include paths — #include <windows.h> resolves without any configuration.

Semantic analysis Dedicated type-checking pass before IR lowering. Collects function signatures, struct field maps, typedef chains, globals, and enum constants. Validates expressions, assignment compatibility, lvalue requirements, and argument counts. Reports errors as line:col: message.

Multi-file compilation -c flag compiles a .c file to a custom .obj (magic CCOBJ001). Multiple .c and .obj inputs can be mixed in one command. Dead code elimination via BFS reachability from main over the merged relocation graph.

PE32+ writer Hand-written PE32+ output — DOS stub, COFF header, optional header, .text / .rdata / .data / .idata sections, import directory, IAT, hint/name entries. Entry trampoline aligns the stack and calls ExitProcess.

Peephole optimizer Tracks which [RBP+N] stack slots hold known values. Eliminates redundant load-after-store sequences and mov r, r no-ops. Runs to a fixed point before encoding.

Import resolution Parses installed .lib archives from the Windows SDK and MSVC toolchain. Reads COFF Short Import Objects to map symbol names to DLLs. No hardcoded lookup table. Unknown externs warn with a --import DLL:FUNC hint.

Precompiled headers Binary serialization of the full parsed AST, all active macro definitions, typedef names, and enum constants. Magic: COMPPCH\x01. Eliminates repeated parsing of heavy SDK headers.

x86-64 encoder Emits raw bytes from machine IR — REX prefixes, ModR/M, SIB, displacements, RIP-relative relocations patched by the PE writer. 8/16/32/64-bit load/store variants. No text assembly stage.

Pipeline

01preprocessormacros · #include · #ifdef · pack
02lexerspan-tracked tokens
03parserrecursive descent · full AST
04semantic analysistypes · scopes · lvalues
05IR loweringtyped IR · struct layout
06codegen + peepholex64 ABI · fixed-point opt
07encoderraw x86-64 bytes · relocs
-c.obj outputCCOBJ001
08linker → .exemerge · DCE · PE32+

Quick start

build

git clone https://github.com/fusexyz/Atlas
cd Atlas
cargo build --release

compile and link

./target/release/compiler \
  examples/sysinfo.c examples/sysinfo_format.c \
  -o sysinfo.exe

./sysinfo.exe

separate compilation

./target/release/compiler -c examples/sysinfo.c        -o sysinfo.obj
./target/release/compiler -c examples/sysinfo_format.c  -o sysinfo_format.obj
./target/release/compiler sysinfo.obj sysinfo_format.obj -o sysinfo.exe

all flags

compiler [-c] <file.c|file.obj>... [-o output]
         [--import DLL:FUNC ...]
         [--make-pch FILE] [--use-pch FILE]

Example output

examples/sysinfo.c + sysinfo_format.c — Win32 APIs via #include <windows.h>

[*] Local System Time:
    Date: 2026-06-10 (YYYY-MM-DD)
    Time: 14:23:07

[*] Host Identity:
    Host Computer Name: DESKTOP-XYZ
    Current User: fuse

[*] Physical Memory (RAM):
    Total RAM: 32678 MiB
    Avail RAM: 18475 MiB
    Memory Load: 43%

[*] CPU and Architecture:
    Architecture: x64 (AMD64)
    Processor Cores: 16

[*] Storage Status (C:\):
    Total Capacity: 476837 MiB
    Free Disk Space: 123456 MiB