Slang Build

Slang Build

For: Building and testing the Slang compiler on any supported platform.

Usage: Referenced by other skills, or invoked directly:

/slang-build [action] [config] [host]
 
  action  build (default) | rebuild | clean | configure
  config  debug (default) | release | releasewithdebug
  host    native (default) | windows | linux

native = the preferred developer build for the current environment. On WSL, native means the Windows build.

Step 1: Parse Arguments

ACTION="build"
CONFIG="debug"
BUILD_HOST="native"
 
for ARG in $ARGUMENTS; do
  ARG_LOWER=$(echo "$ARG" | tr '[:upper:]' '[:lower:]')
  case "$ARG_LOWER" in
    build|rebuild|clean|configure)   ACTION="$ARG_LOWER" ;;
    debug|release|releasewithdebug)  CONFIG="$ARG_LOWER" ;;
    native|windows|linux)            BUILD_HOST="$ARG_LOWER" ;;
  esac
done
 
case "$CONFIG" in
  debug)            CMAKE_BUILD_PRESET="debug";                BIN_PATH="build/Debug/bin" ;;
  release)          CMAKE_BUILD_PRESET="release";              BIN_PATH="build/Release/bin" ;;
  releasewithdebug) CMAKE_BUILD_PRESET="releaseWithDebugInfo"; BIN_PATH="build/RelWithDebInfo/bin" ;;
esac

Config reference

Step 2: Detect Platform and Select Tools

case "$(uname -s)" in
  Darwin)               PLATFORM="macos" ;;
  Linux)                PLATFORM="linux" ;;
  MINGW*|MSYS*|CYGWIN*) PLATFORM="windows" ;;
  *)                    PLATFORM="unknown" ;;
esac
 
if grep -qi microsoft /proc/version 2>/dev/null; then
  PLATFORM="wsl"
fi
 
# Resolve "native" build host.
if [ "$BUILD_HOST" = "native" ]; then
  if [ "$PLATFORM" = "wsl" ]; then
    BUILD_HOST="windows"
  else
    BUILD_HOST="$PLATFORM"
  fi
fi

Select tool binaries

On WSL, git and git.exe (and cmake / cmake.exe) both exist on PATH but are not interchangeable. Pick the binary that matches the chosen build host and use it consistently.

require_tool() {
  if command -v "$1" >/dev/null 2>&1; then printf '%s\n' "$1"; return 0; fi
  printf '%s\n' "$2" >&2; return 1
}
 
if [ "$BUILD_HOST" = "windows" ] && [ "$PLATFORM" = "wsl" ]; then
  GIT=$(require_tool git.exe   "Missing git.exe — install Git for Windows or rerun with host=linux.") || exit 1
  CMAKE=$(require_tool cmake.exe "Missing cmake.exe — install CMake on Windows or rerun with host=linux.") || exit 1
  CMAKE_CONFIGURE_PRESET="vs2026-dev"
  CMAKE_CONFIGURE_ARGS="-DSLANG_IGNORE_ABORT_MSG=ON -DSLANG_EMBED_CORE_MODULE=OFF"
elif [ "$BUILD_HOST" = "windows" ]; then
  GIT=$(require_tool git       "Missing git.") || exit 1
  CMAKE=$(require_tool cmake.exe "Missing cmake.exe.") || exit 1
  CMAKE_CONFIGURE_PRESET="vs2026-dev"
  CMAKE_CONFIGURE_ARGS="-DSLANG_IGNORE_ABORT_MSG=ON -DSLANG_EMBED_CORE_MODULE=OFF"
else
  GIT=$(require_tool git   "Missing git.") || exit 1
  CMAKE=$(require_tool cmake "Missing cmake.") || exit 1
  CMAKE_CONFIGURE_PRESET="default"
  CMAKE_CONFIGURE_ARGS="-DSLANG_EMBED_CORE_MODULE=OFF"
fi

Preset fallback for Windows hosts: try vs2026-dev first, then vs2022-dev, then vs2019-dev.

Use $GIT and $CMAKE everywhere from here on. Append .exe to any other Windows-hosted tool you invoke (slangc.exe, slang-test.exe, python.exe, gh.exe).

Configure flags explained

• -DSLANG_IGNORE_ABORT_MSG=ON — suppresses modal abort dialogs (unattended Windows builds).
• -DSLANG_EMBED_CORE_MODULE=OFF — skips embedding the core module binary; cleaner stack traces.

Platform capabilities

On macOS, CUDA and D3D tests are skipped, not failed. Check skip counts.

Step 3: Check Prerequisites (Linux/WSL-linux only)

for pkg in cmake ninja-build python3 python3-dev libssl-dev; do
  dpkg -l "$pkg" 2>/dev/null | grep -q "^ii" || echo "MISSING: $pkg"
done

If anything missing, request all of them in one install_packages call — the container rebuilds and you'll restart from scratch.

Optional: clang, llvm (for -DSLANG_ENABLE_LLVM=ON).

Step 4: Dispatch by Action

clean      → A (clean)                            → done
configure  → B (submodules + configure)           → done
build      → B (if no build/), then C (build)
rebuild    → A (clean), then B, then C

A. Clean

Rename build/ rather than deleting in place. Renames are atomic; in-place deletes on Windows fail mid-tree when files are open.

bash / WSL / Git Bash:

if [ ! -d "build" ]; then echo "Nothing to clean."; exit 0; fi
BUILD_TRASH="build_$(date +%s)_$$"
if mv build "$BUILD_TRASH" 2>/dev/null; then
  echo "Renamed build/ to $BUILD_TRASH"
  rm -rf "$BUILD_TRASH" &
  echo "Background delete started (PID $!)"
else
  echo "ERROR: build/ in use. Close debuggers / IDE / running binaries and retry."
  exit 1
fi

Windows PowerShell:

if (-not (Test-Path build -PathType Container)) { Write-Host "Nothing to clean."; exit 0 }
$BuildTrash = "build_$([Guid]::NewGuid().ToString('N'))"
if (Rename-Item -Path build -NewName $BuildTrash -ErrorAction SilentlyContinue) {
    Write-Host "Renamed build/ to $BuildTrash"
    Start-Job { Remove-Item -Recurse -Force $using:BuildTrash } | Out-Null
} else {
    Write-Error "build\ in use. Close debuggers / IDE / running binaries and retry."
    exit 1
}

B. Submodules + Configure

$GIT submodule update --init --recursive

Host-cache guard — bail if the existing build/ was configured for a different host:

if [ -f build/CMakeCache.txt ]; then
  case "$BUILD_HOST" in
    windows) EXPECTED="Windows" ;;
    linux)   EXPECTED="Linux" ;;
    macos)   EXPECTED="Darwin" ;;
  esac
  if ! grep -q "^CMAKE_HOST_SYSTEM_NAME:INTERNAL=$EXPECTED\$" build/CMakeCache.txt; then
    echo "Existing build/ is for a different host. Run action 'clean' first, then retry."
    exit 1
  fi
fi

Configure (bash / WSL / Git Bash):

$CMAKE --preset "$CMAKE_CONFIGURE_PRESET" $CMAKE_CONFIGURE_ARGS

Configure (Windows PowerShell):

cmake.exe --preset vs2026-dev -DSLANG_IGNORE_ABORT_MSG=ON -DSLANG_EMBED_CORE_MODULE=OFF

Fallback: GitHub API rate limit

If configure fails with a GitHub API rate-limit error, compute the release tag and pass SLANG_SLANG_LLVM_BINARY_URL explicitly:

$GIT fetch --tags
tagFullVersion="$($GIT describe --tags --match 'v20[2-9][0-9].[0-9]*')"
tagVersion="${tagFullVersion%%-*}"
tag="${tagVersion#v}"
 
LINUX_URL="https://github.com/shader-slang/slang/releases/download/$tagVersion/slang-$tag-linux-x86_64.zip"
WIN_URL="https://github.com/shader-slang/slang/releases/download/$tagVersion/slang-$tag-windows-x86_64.zip"
 
# Re-run configure with the URL matching your build host:
$CMAKE --preset "$CMAKE_CONFIGURE_PRESET" $CMAKE_CONFIGURE_ARGS \
  -DSLANG_SLANG_LLVM_BINARY_URL="$WIN_URL"   # or "$LINUX_URL"

Optional: sccache

Pass -DSLANG_USE_SCCACHE=ON for faster rebuilds.

Pitfall: sccache can return cached objects that miss local debug changes. If printf / IR-dump edits seem to have no effect:

• Force recache: SCCACHE_RECACHE=1 $CMAKE --build --preset "$CMAKE_BUILD_PRESET" --target slangc
• Or reconfigure with -DSLANG_USE_SCCACHE=OFF.

C. Build

bash / WSL / Git Bash:

$CMAKE --build --preset "$CMAKE_BUILD_PRESET" --target slangc slang-test \
  >/dev/null 2>&1 || \
$CMAKE --build --preset "$CMAKE_BUILD_PRESET" --target slangc slang-test

Windows PowerShell:

cmake.exe --build --preset $CMAKE_BUILD_PRESET --target slangc slang-test *>$null
if ($LASTEXITCODE -ne 0) {
    cmake.exe --build --preset $CMAKE_BUILD_PRESET --target slangc slang-test
}

The redirect-then-retry pattern keeps successful builds token-quiet; on failure the second run prints the real errors.

Monitoring a fresh / clean build

Fresh and clean builds are full compiles: 10–20 min on an 8-core CPU, less with a warm sccache.

• After kicking one off, don't poll for 10–15 minutes.
• Still running after that? Check every 2–5 minutes, not seconds.
• Skip tail, ps, verbose progress checks unless you suspect a hang.

Verify outputs

ls "$BIN_PATH"/slangc*
ls "$BIN_PATH"/slang-test*

On WSL Windows-hosted builds, require slangc.exe and slang-test.exe. If only the non-.exe versions exist, stop — they are from a different build.

Testing

slang-test must run from the repository root.

# All tests, multi-server (10–30 min)
"$BIN_PATH"/slang-test -use-test-server -server-count 8
 
# Specific test file
"$BIN_PATH"/slang-test tests/path/to/test.slang
 
# Unit tests
"$BIN_PATH"/slang-test slang-unit-test-tool/

Test directives

• CPU compute: //TEST:COMPARE_COMPUTE(filecheck-buffer=CHECK):-cpu -output-using-type
• GPU compute: //TEST:COMPARE_COMPUTE(filecheck-buffer=CHECK):-dx12 -output-using-type
• Interpreter: //TEST:INTERPRET(filecheck=CHECK):
• Diagnostic: //DIAGNOSTIC_TEST:SIMPLE(diag=CHECK):-target spirv

SPIRV validation

Set SLANG_RUN_SPIRV_VALIDATION=1 and use slangc -target spirv. Do not use the system's spirv-val.

Debugging Tools

IR dump — always combine -dump-ir with -target and -o:

slangc -dump-ir -target spirv-asm -o tmp.spv test.slang | python extras/split-ir-dump.py
slangc -dump-ir-before lowerGenerics -dump-ir-after lowerGenerics \
       -target spirv-asm -o tmp.spv test.slang > pass.dump

InstTrace — trace where a problematic IR instruction was created:

python3 ./extras/insttrace.py <debugUID> ./build/Debug/bin/slangc tests/my-test.slang -target spirv

RTX Remix shader repro: ./extras/repro-remix.sh clones dxvk-remix, swaps in your local Slang, compiles all shaders with SPIRV validation.

SlangPy compat testing: clone external/slangpy, then:

CMAKE_ARGS="-DSGL_LOCAL_SLANG=ON -DSGL_LOCAL_SLANG_DIR=../.. -DSGL_LOCAL_SLANG_BUILD_DIR=build/Debug" \
  python -m pip install -e .

CI

gh run list --repo shader-slang/slang --workflow=ci.yml --limit 5
gh run view <run-id> --log-failed

CLI Gotchas

Slang uses single dashes for multi-character options: -help, -target spirv, -dump-ir, -stage compute. Not double dashes.

Do NOT use: -dump-ast, -dump-intermediate-prefix, -dump-intermediates, -dump-ir-ids, -serial-ir, -dump-repro, -load-repro, -extract-repro, -category, -api.