libexhelper

A lightweight C/assembly library for bridging exception handling between managed and native code using the DWARF unwinder.

Overview

A re-implementation of MonoMod's libexhelper, consolidated into a single cross-platform codebase. The original had separate implementations for each platform/architecture combination, which was difficult to maintain. This version uses unified C and assembly sources with platform-specific macros for Linux/macOS on x86_64/arm64.

libexhelper provides three exported functions for exception handling interoperability:

• eh_get_exception_ptr() - Returns a pointer to the thread-local current exception pointer
• eh_managed_to_native(target) - Calls native code from managed context, catching any C++ exceptions
• eh_native_to_managed(target) - Calls managed code from native context, rethrowing any pending exceptions

Supported Platforms

Platform	Architecture
Linux	x86_64, arm64
macOS	x86_64, arm64

Building

Using Clang (recommended for smallest binary)

./build.sh

Environment Variables

Variable	Default	Description
MODE	debug	Build mode: debug or release
TEST	0	Build and run test executable: 0 or 1
OS	auto-detect	Target OS: Darwin or Linux
PLATFORM	auto-detect	Platform name: e.g. macos, linux, linux-gnu
ARCH	auto-detect	Target architecture: x86_64 or arm64
CC	clang	C compiler (for zig zig cc)
CXX	clang++	C++ compiler (for zig zig c++)

Examples

# Release build
MODE=release ./build.sh

# Build and run tests
MODE=release TEST=1 ./build.sh

# Cross-compile for Linux arm64 on macOS
OS=Linux PLATFORM=linux ARCH=arm64 ./build.sh

Outputs to build/release/bin/ and build/debug/bin/.

Using Zig (recommended for cross-compilation)

# Native build
zig build -Doptimize=ReleaseFast

# Cross-compile for Linux x86_64
zig build -Doptimize=ReleaseFast -Dtarget=x86_64-linux-gnu

# Cross-compile for Linux arm64
zig build -Doptimize=ReleaseFast -Dtarget=aarch64-linux-gnu

Outputs to zig-out/lib/.

Testing

# With build.sh
TEST=1 ./build.sh

# With zig
zig build test

Contributing

Contributions are welcome! Feel free to open issues and pull requests.

License

MIT