w2c2

Translates WebAssembly modules to C. Inspired by wabt's wasm2c.

Features

• Implements the WebAssembly Core Specification 1.0
• Passes 99.9% of the WebAssembly core semantics test suite
• Written in C89 and generates C89
• Support for older operating systems and architectures
• Support for big-endian systems
• Streaming compilation, low memory usage
• Parallel compilation into multiple files
• WASI implementation which is able to run clang.wasm

Performance

• Coremark 1.0: ~7% slower than native

Compilation

make

To enables certain features, list them in the FEATURES variable passed to make, e.g. make FEATURES="threads":

• Parallel compilation requires pthreads on the host system. Add threads to FEATURES.
• If the host system has support for getopt, add getopt to FEATURES.
• Generating debug information requires libdwarf on the host system. Add debugging to FEATURES.

Usage

Compile module.wasm to module.c:

./w2c2 -o module.c module.wasm

Parallel Compilation

Compile module.wasm using 12 concurrent jobs into multiple files with 100 functions each:

./w2c2 -o module_directory -j 12 -f 100 module.wasm

Examples

Coremark:

cd examples/coremark
./coremark

Testing

Requires Python 3 and wabt (for wast2json).

cd tests
make gen
make run-tests

WASI Status

• [x] args_get
• [x] args_sizes_get
• [x] clock_res_get
• [x] clock_time_get
• [x] environ_get
• [x] environ_sizes_get
• [ ] fd_advise
• [ ] fd_allocate
• [x] fd_close
• [ ] fd_datasync
• [x] fd_fdstat_get
• [ ] fd_fdstat_set_flags
• [ ] fd_fdstat_set_rights
• [x] fd_filestat_get
• [ ] fd_filestat_set_size
• [ ] fd_filestat_set_times
• [x] fd_pread
• [x] fd_prestat_get
• [x] fd_prestat_dir_name
• [ ] fd_pwrite
• [x] fd_read
• [x] fd_readdir
• [ ] fd_renumber
• [x] fd_seek
• [ ] fd_sync
• [x] fd_tell
• [x] fd_write
• [x] path_create_directory
• [x] path_filestat_get
• [ ] path_filestat_set_times
• [ ] path_link
• [x] path_open
• [x] path_readlink
• [x] path_remove_directory
• [x] path_rename
• [x] path_symlink
• [x] path_unlink_file
• [ ] poll_oneoff
• [x] proc_exit
• [x] random_get
• [ ] sched_yield
• [ ] sock_recv
• [ ] sock_send
• [ ] sock_shutdown

Development

To build a debug release, pass BUILD=debug to make.

To enable sanitizers, list them in the SANITIZERS variable passed to make, e.g. make BUILD=debug SANITIZERS="base clang address thread".

• base enables the Undefined Behavior Sanitizer
• clang enables Clang-specific sanitizers
• thread enables the Thread Sanitizer
• address enables the Address Sanitizer