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This library provides stubs for POSIX compatibility when compiling sources using the WASI SDK. The WASI SDK and the accomanying wasi-libc do provide some POSIX functionality, but many functions that are not currently supported or do not make sense in the context of WASM are missing. This can make it difficult to compile sources to WASI that expect POSIX compatibility.
The library in this project aims to fill the gaps between POSIX and WASI. In many cases, the implementation of functions will simply return an error code, but it will allow many 3rd party sources to compile using WASI and access any functionality that doesn't require the stubbed out functions.
Some functions (e.g., getpid, getuid, getgid) are implemented to return
a static value given at compile time or an environment variable specified
at runtime. This allows you to more closely emulate some POSIX functions
in your environment as needed.
The build requirements for WASIX are the same as for WASI SDK. The Makefile may need to be changed to reflect the installation path of WASI SDK and wasi-libc.
To build libwasix.a, simply run the Makefile:
make all
The default behavior for WASIX is to return an error code if a function is not implemented. Depending on how the library is used, it may be preferable to have the process abort when an unimplemented function is called. To enable this behavior use the following build command:
make all_abort
To use libwasix.a, add the following options to your compilation step:
-isystem ${WASIX_DIR}/include
Then add the following options to your link step:
-L${WASIX_DIR} -lwasix
Some functions in WASIX can be configured to return a static value rather than an error. The following functions can be configured in the specified ways.
| Function | Environment Variable | Compile-Time Definition | Default |
|---|---|---|---|
getpid |
WASIX_PID |
-D_WASIX_PID=value |
66600 |
getppid |
WASIX_PPID |
-D_WASIX_PPID=value |
55500 |
getuid |
WASIX_UID |
-D_WASIX_UID=value |
1 |
geteuid |
WASIX_EUID |
-D_WASIX_EUID=value |
1 |
getgid |
WASIX_GID |
-D_WASIX_GID=value |
100 |
getegid |
WASIX_EGID |
-D_WASIX_EGID=value |
100 |
Some functions in WASIX do nothing and return a successful return value. These
include chmod, fchmod, chown, fchown, and umask (returns 0755).
Currently, threads are stubbed out and do not allow new threads to be created. We are planning on doing a thread implementation based on async which will enable threads to be created although only one thread will actually be working at any time.
Some of the structure definitions in the header and source files were taken from the WASI SDK sources and modified to include additions to assist in the compilation of various libraries. The WASI SDK uses the same license as this project.