---
sidebar_label: Build system
---
# Build System
## Compiler Backends
DCR supports 7 compilation backends. Selection is automatic based on file extension and `build.compiler` value.
| Backend | Files | When used |
|---------|-------|-----------|
| `unix_cc` | `.c`, `.cpp`, `.cxx`, `.cc`, `.S` | gcc/clang on Linux/macOS/BSD |
| `msvc` | `.c`, `.cpp`, `.cxx`, `.cc` | Windows (cl, clang-cl) |
| `gas` | `.s` | ARM/ARM64 assembler (no preprocessor) |
| `nasm` | `.asm`, `.s` | x86/x86_64 NASM assembler |
| `masm` | `.asm` | MASM (ml/ml64) on Windows |
| `fasm` | `.asm`, `.fasm` | Flat Assembler |
| `llvm_ir` | `.ll` | LLVM IR via `llc -filetype=obj` |
## Qt Support
DCR provides native Qt support for automatic meta-object handling (MOC, UIC, RCC).
Enable it by setting `build.qt = true` in `dcr.toml`. DCR will automatically detect Qt-related files (`.ui`, `.qrc`, `.h` with `Q_OBJECT`) and process them.
```toml
[build]
qt = true
```
*Note: Requires `qt6` modules (Core, Widgets, Gui, Svg) installed via `pkg-config`.*
Advanced customization is still possible via `build.steps` if special handling is needed:
```toml
[build.steps]
moc = "moc {in} -o {out}"
```
### Unix CC
- Compiler resolved via `resolve_compiler()`: `DCR_COMPILER` > `DCR_CC` > `[toolchain]` > `build.compiler` > `PATH`
- Supports `.d` files for header dependency tracking
- Flags: `-std=`, `-MMD -MF`, `-c -o`, `-I`, `-L`, `-l`
- Conditional flags based on config:
- `freestanding` or bare-metal target: `-ffreestanding` (compile), `-nostdlib -static` (link)
- `lto`: `-flto` (compile + link)
- `panic = "abort"`: `-fno-exceptions` (C++ only), `-fno-unwind-tables`, `-fno-asynchronous-unwind-tables`
### MSVC
- Supports cl.exe and clang-cl.exe
- Flags: `/std:`, `/Fo:`, `/Fe:`, `/I`, `/link`
### GAS / NASM / MASM / FASM / LLVM-IR
- GAS: `-I`, `-c -o`, `--defsym`
- NASM: `-I`, `-o`, `-D`, `-f` (format: win64/elf64/macho64/macho32/elf32; **`bin` when `kind = "flat-bin"`**)
- MASM: `/nologo /c /Fo<obj> <source>`
- FASM: `<source> <output>` (output path is the object file)
- LLVM IR: `-filetype=obj <source> -o <output>`
## Incremental Builds
Three levels of incrementality:
1. **mtime** — if output is newer than all inputs, skip
2. **`.d` files** — header change tracking (including transitive)
3. **SHA256 fingerprint** — recompile if compiler flags changed (stored in `.dcr_fingerprint`)
## Parallel Compilation
- `thread::scope` for thread pool
- Atomic task queue (`AtomicU64`)
- Mutex on stdout (`OUTPUT_MUTEX`)
- Thread count = `available_parallelism()`, capped by `build.codegen-units` if set
## Build Kinds
| Kind | Type | Path (Linux example) |
|------|------|---------------------|
| `bin` | Executable | `target/<triple>/<profile>/<name>` (.exe on Windows) |
| `staticlib` | Static library | `target/<triple>/<profile>/lib<name>.a` (.lib) |
| `sharedlib` | Dynamic library | `target/<triple>/<profile>/lib<name>.so` (.dll/.dylib) |
| `efi` | UEFI application | `target/<triple>/<profile>/<name>.efi` |
| `elf` | ELF without stdlib | `target/<triple>/<profile>/<name>` |
| `none` | Compile only, no link | — |
| `custom` | Full filename+extension control | `target/<triple>/<profile>/<filename>.<extension>` |
| `flat-bin` | Raw binary | ASM: `<stem>.bin` (NASM `-f bin` / FASM / GAS·MASM·LLC via objcopy); C/C++: `<name>.bin` (link + objcopy) |
## Disk images (`[archive]`)
After a successful build, if `[archive]` is present in `dcr.toml`, DCR formats a FAT volume and copies files from `layout` into the image. See [dcr.toml → archive](/docs/reference/dcr-toml#archive).
## Build Steps
DCR supports pre-build and post-build steps:
- `build.steps` — commands before compilation
- `build.post_steps` — commands after compilation
Substitutions: `{stem}`, `{in}`, `{out}`, `{profile}`, `{version}`, `{name}`.
Example Qt codegen via build steps:
```toml
[build.steps]
moc = "moc {in} -o {out}"
```
## pkg-config
Automatic lookup (read from raw config):
```toml
[build]
pkg_config = ["sdl2", "gl"]
```
DCR runs `pkg-config --cflags sdl2 gl` and `pkg-config --libs sdl2 gl` and adds results to compiler/linker flags.
## Variable Substitution
Supported variables:
| Variable | Description |
|----------|-------------|
| `{version}` | Package version |
| `{version_major}` | Major version part |
| `{version_minor}` | Minor version part |
| `{version_patch}` | Patch version |
| `{version_suffix}` | Suffix (e.g., `-rc1`) |
| `{version_suffix_dash}` | Suffix with dash |
| `{profile}` | Profile name (debug/release) |
| `{name}` | Package name |