bdfbb54520
* Link `populate_environ` only if we actually need environment variables. This avoids linking in the environment variable initialization code, and the __wasi_environ_sizes_get and __wasi_environ_get imports, in programs that don't use environment variables. This also removes the "___environ" (three underscores) alias symbol, which is only in musl for backwards compatibility. * Switch to //-style comments. * If malloc fails, don't leave `__environ` pointing to an uninitialized buffer. * Fix a memory leak if one malloc succeeds and the other fails. * Use calloc to handle multiplication overflow. This also handles the NULL terminator. * Don't initialize __environ until everything has succeeded. * Avoid leaking in case __wasi_environ_get fails. * Handle overflow in the add too. * Add #include <stdlib.h> for malloc etc. * If the environment is empty, don't allocate any memory. |
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|---|---|---|
| basics | ||
| dlmalloc | ||
| expected/wasm32-wasi | ||
| libc-bottom-half | ||
| libc-top-half | ||
| .azure-pipelines.yml | ||
| .gitignore | ||
| CODE_OF_CONDUCT.md | ||
| LICENSE | ||
| Makefile | ||
| README.md | ||
WASI Libc
This is a work in progress. It's usable for many purposes, though the APIs aren't stable yet.
What is this?
It's several things.
First, it's a usable libc. It builds a "libc" which can be used by compilers, such as Clang 8.0, using the wasm32-wasi target. It's a work in progress, but it is already sufficient to run basic programs.
Second, it's a "reference" implementation, which means the interfaces defined
here can be used by other tools and libraries, even if they don't use all the
actual implementations here. For example, we don't expect everyone will want
to use the exact malloc implementation provided here, but tools and
libraries using an ABI-compatible malloc interface will be able to
interoperate regardless of which actual implementation is used.
Third, it's an example showing the use of the WASI API. The libc functionality is implemented using calls to WASI functions.
Usage
The easiest way to get started with this is to use one of the prepackaged releases.
Building from source
To build a WASI sysroot from source, obtain a WebAssembly-supporting C compiler (currently this is only clang 8+, though we'd like to support other compilers as well), and then run:
make WASM_CC=/path/to/clang/with/wasm/support \
WASM_AR=/path/to/llvm-ar \
WASM_NM=/path/to/llvm-nm
This makes a directory called "sysroot", by default. See the top of the Makefile for customization options.
To use the sysroot, use the --sysroot= option:
/path/to/wasm/supporting/c/compiler --sysroot=/path/to/the/newly/built/sysroot ...
to run the compiler using the newly built sysroot.