sleepy
c6eebf62c2
- Added BUILD_FROM_SOURCE.md with detailed error analysis - Documented SDK version issues and miniaudio cross-compilation problems - Provided alternative approaches and recommendations
139 lines
4.6 KiB
Markdown
139 lines
4.6 KiB
Markdown
# Building LiteRT-LM for iOS from Source
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## Status: Build Issues Encountered
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We attempted to build LiteRT-LM iOS binaries from source but encountered significant cross-compilation challenges with Bazel.
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## Build Attempt Summary
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### Environment
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- **Machine**: Mac Mini (Apple Silicon)
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- **OS**: macOS 15.x
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- **Xcode**: CommandLineTools SDK 15.5
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- **Bazel**: 7.6.1 (via Bazelisk)
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### Commands Attempted
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```bash
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# Clone repository
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git clone https://github.com/google-ai-edge/LiteRT-LM.git
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cd LiteRT-LM
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# Build for iOS device (arm64)
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bazel build --config=ios_arm64 //c:engine
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# Build for iOS simulator (arm64)
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bazel build --config=ios_sim_arm64 //c:engine
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```
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### Issues Encountered
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#### 1. SDK Version Mismatch
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```
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ERROR: SDK version [10.11] for platform [MacOSX] is unsupported
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xcrun: error: SDK "macosx10.11" cannot be located
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```
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**Attempted Fix**: Created `.bazelrc.user` with `--macos_sdk_version=15.5`
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#### 2. OpenGLES Header Missing
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```
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fatal error: 'OpenGLES/EAGL.h' file not found
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#import <OpenGLES/EAGL.h>
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```
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**Root Cause**: The miniaudio library uses AVFoundation framework which on macOS includes CoreImage, which requires OpenGLES headers. When cross-compiling for iOS from macOS, Bazel incorrectly uses the host macOS SDK for some compilation steps.
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**Attempted Fixes**:
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- Patched `BUILD.miniaudio` to use different SDK frameworks
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- Patched `runtime/components/preprocessor/BUILD` to use C version instead of ObjC version
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- Neither fully resolved the issue
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#### 3. Objective-C Syntax Errors
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```
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error: expected identifier or '('
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@class NSInvocation, NSMethodSignature, NSCoder, NSString, NSEnumerator;
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```
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**Root Cause**: After switching to C version of miniaudio, the C compiler tried to parse Objective-C headers.
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### Patches Applied
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1. **`.bazelrc.user`** - SDK version override:
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```
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build --macos_sdk_version=15.5
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build --ios_sdk_version=18.0
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```
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2. **`BUILD.miniaudio`** - Added more SDK frameworks
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3. **`runtime/components/preprocessor/BUILD`** - Changed miniaudio selection to use C version
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### Why These Issues Occur
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1. **Complex Cross-Compilation**: LiteRT-LM uses Bazel with rules_apple for iOS builds, which requires precise toolchain configuration.
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2. **Audio Dependencies**: The miniaudio library needs platform-specific audio backends (AVFoundation on iOS/macOS), which creates complications during cross-compilation.
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3. **Host vs Target Toolchains**: Bazel is mixing host (macOS) and target (iOS) toolchains, causing SDK mismatches.
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## Alternative Approaches
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### Option 1: Use Full Xcode (Not CommandLineTools)
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The build may work better with full Xcode installation which has proper iOS SDKs:
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```bash
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sudo xcode-select -s /Applications/Xcode.app/Contents/Developer
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```
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### Option 2: Build on Linux with iOS Cross-Compilation
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Use a Linux machine with proper iOS cross-compilation toolchain setup.
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### Option 3: Wait for Official Binaries
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Google may provide prebuilt iOS binaries in future releases.
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### Option 4: Use MediaPipe Tasks (Working Alternative)
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While deprecated, MediaPipe Tasks LLM Inference has a working Swift API:
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```ruby
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pod 'MediaPipeTasksGenAI', '~> 0.10.0'
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```
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### Option 5: Use LiteRT C API with Custom Bridge
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Build only the core LiteRT runtime (without LLM features) and implement the conversation handling in Swift.
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## Recommendation
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**For immediate use**: Use the Objective-C++ bridge pattern with stub implementation (already provided in the project) and wait for:
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1. Official LiteRT-LM iOS binaries from Google
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2. LiteRT-LM Swift API release (marked as "coming soon")
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**For production**: Consider building on a CI service like GitHub Actions with proper macOS/iOS build environment.
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## Build Scripts
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The following scripts were created during the build attempt:
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### `/tmp/build_litert_lm_ios.sh`
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Main build script that attempts to build both device and simulator libraries.
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### `/tmp/patch_miniaudio_build.py`
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Patches the miniaudio BUILD file to add additional SDK frameworks.
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### `/tmp/patch_preprocessor_build.py`
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Patches the preprocessor BUILD file to use C version of miniaudio.
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## Next Steps
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To successfully build from source, you would need to:
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1. Install full Xcode (not just CommandLineTools)
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2. Set up proper iOS signing certificates
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3. Modify the Bazel build configuration to handle audio dependencies correctly
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4. Potentially disable audio features entirely for a text-only build
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5. Build in a clean environment with sufficient disk space (20GB+)
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## References
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- [LiteRT-LM Build Instructions](https://github.com/google-ai-edge/LiteRT-LM/blob/main/docs/getting-started/build-and-run.md)
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- [Bazel Apple Rules](https://github.com/bazelbuild/rules_apple)
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- [iOS Cross-Compilation with Bazel](https://bazel.build/concepts/platforms)
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