| # Fuchsia's libc |
| |
| Fuchsia's libc started as a fork of musl libc. It has since diverged |
| significantly, but the approximate source code layout remains the same. The |
| source can be found in |
| [`zircon/third_party/ulib/musl`](/zircon/third_party/ulib/musl). |
| |
| TODO(https://fxbug.dev/42106460) Type more here. |
| |
| ## Standards |
| |
| ### C11 |
| |
| Fuchsia's libc supports most of the [C11][c11std] standard. This |
| in particular includes the atomic and threading portions of the |
| standard library. |
| |
| ### POSIX |
| |
| Fuchsia implements a subset of POSIX. |
| |
| Things at least partially supported include the basics of POSIX I/O |
| (open/close/read/write/stat/...), and pthreads (threads and mutexes). |
| |
| On Fuchsia, the portion of file paths beginning with a sequence of |
| `..` is resolved locally. See [this writeup][dotdot] for more |
| information. |
| |
| Similarly, symlinks are not supported on Fuchsia. |
| |
| Conspicuously not supported are UNIX signals, fork, and exec. |
| |
| ## FDIO |
| |
| Fuchsia's libc does not directly support I/O operations. Instead it |
| provides weak symbols that another library can override. This is |
| typically done by [fdio.so][fdio]. |
| |
| ## Linking |
| |
| Statically linking libc is not supported. Everything dynamically links libc.so. |
| |
| ## Dynamic linking and loading |
| |
| libc.so is also the dynamic linker. |
| |
| [c11std]: https://en.wikipedia.org/wiki/C11_(C_standard_revision) |
| [dotdot]: /docs/concepts/filesystems/dotdot.md |
| [fdio]: /sdk/lib/fdio |
