add stubs for statvfs, chmod, etc.
#463
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Per WebAssembly/wasi-sdk#373, LLVM's libc++ no longer allows us to enable `<fstream>` and `<filesystem>` separately -- it's both or neither. Consequently, we either need to patch libc++ to not use `statvfs`, `chmod`, etc. or add stub functions for those features to `wasi-libc`. Since we're planning to eventually support those features with WASI Preview 2 and beyond, it makes sense to do the latter. Note that since libc++ uses `DT_SOCK`, I've added a definition for it -- even though WASI Preview 1 does not define it. No Preview 1 file will ever have that type, so code that handles that type will never be reached, but defining it allows us to avoid WASI-specific patches to libc++. Related to `DT_SOCK`, I had to change the `S_IFIFO` value so it does not conflict with `S_IFSOCK`, thereby avoiding ambiguity in `__wasilibc_iftodt`. Signed-off-by: Joel Dice <[email protected]>
yamt
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Jan 23, 2024
| char *realpath (const char *__restrict, char *__restrict); | ||
| #endif |
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Yes -- realpath is one of the functions libcxx's <filesystem> relies on, although I just realized I neglected to add realpath.c to LIBC_TOP_HALF_MUSL_SOURCES in the Makefile, and I'm not sure if that implementation is what we want (vs. a stub), so I'll need to take a closer look.
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it was intentionally disabled in the header. #82
if you are going to add a realpath implementation anytime soon, it's great. please go ahead.
otherwise, it's probably better to revert this part for now, until the implementation gets ready.
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Reverting this part causes the libcxx build to fail, so I don't think that's an option (unless we want to patch libcxx). I've added a stub in #473, which I believe is the best we can do right now short of patching libcxx.
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Update: the stub wasn't needed -- turns out musl's realpath implementation works fine.
dicej
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In WebAssembly#463, I added stubs for `statvfs`, `chmod`, etc. but forgot to add one for `realpath`, which is also required by `libc++`'s `<filesystem>` implementation. Signed-off-by: Joel Dice <[email protected]>
sunfishcode
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* provide a `realpath` stub In #463, I added stubs for `statvfs`, `chmod`, etc. but forgot to add one for `realpath`, which is also required by `libc++`'s `<filesystem>` implementation. Signed-off-by: Joel Dice <[email protected]> * remove `realpath` stub and use musl's version instead Signed-off-by: Joel Dice <[email protected]> --------- Signed-off-by: Joel Dice <[email protected]>
rootbeer
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Point to the correct header files where the wasi-libc constants are defined that the Zig lib/std/c.zig is replicating. Zig's current copy of wasi-libc has a bug in the file-mode constants. Both S_IFIFO and S_IFSOCK are 0xc000, but S_IFIFO should be 0x1000. See WebAssembly/wasi-libc#463.
rootbeer
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Point to the correct header files where the wasi-libc constants are defined that the Zig lib/std/c.zig is replicating. Zig's current copy of wasi-libc has a bug in the file-mode constants. Both S_IFIFO and S_IFSOCK are 0xc000, but S_IFIFO should be 0x1000. See WebAssembly/wasi-libc#463.
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As of a recent fix included in LLVM 17[1] and wasi-libc fix[2], we can enable `LIBCXX_ENABLE_FILESYSTEM` in libcxx build for WebAssembly/WASI. This allows us to use `<filesystem>`, `<fstream>`, etc in C++ code. [1]: llvm/llvm-project@66a562d [2]: WebAssembly/wasi-libc#463
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Per WebAssembly/wasi-sdk#373, LLVM's libc++ no longer allows us to enable
<fstream>and<filesystem>separately -- it's both or neither. Consequently, we either need to patch libc++ to not usestatvfs,chmod, etc. or add stub functions for those features towasi-libc. Since we're planning to eventually support those features with WASI Preview 2 and beyond, it makes sense to do the latter.Note that since libc++ uses
DT_SOCK, I've added a definition for it -- even though WASI Preview 1 does not define it. No Preview 1 file will ever have that type, so code that handles that type will never be reached, but defining it allows us to avoid WASI-specific patches to libc++.Related to
DT_SOCK, I had to change theS_IFIFOvalue so it does not conflict withS_IFSOCK, thereby avoiding ambiguity in__wasilibc_iftodt.