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[WasmFS] Fix argument name for open in the Node backend. NFC #26597

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[WasmFS] Fix argument name for open in the Node backend. NFC #26597

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4 changes: 2 additions & 2 deletions src/lib/libwasmfs_node.js
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Original file line number Diff line number Diff line change
Expand Up @@ -171,8 +171,8 @@ addToLibrary({
},

_wasmfs_node_open__deps: ['$wasmfsTry'],
_wasmfs_node_open: (path_p, mode_p) => {
return wasmfsTry(() => fs.openSync(UTF8ToString(path_p), UTF8ToString(mode_p)));
_wasmfs_node_open: (path_p, flags_p) => {
return wasmfsTry(() => fs.openSync(UTF8ToString(path_p), UTF8ToString(flags_p)));
},

_wasmfs_node_rename__deps: ['$wasmfsTry'],
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2 changes: 1 addition & 1 deletion system/lib/wasmfs/backends/node_backend.h
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Expand Up @@ -37,7 +37,7 @@ int _wasmfs_node_symlink(const char *target, const char *linkpath);
int _wasmfs_node_readlink(const char *path, const char *buf, int bufsize);

// Open the file and return the underlying file descriptor.
[[nodiscard]] int _wasmfs_node_open(const char* path, const char* mode);
[[nodiscard]] int _wasmfs_node_open(const char* path, const char* flags);
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@sbc100 sbc100 Apr 1, 2026

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Isn't mode the correct name for the string arguments like w+ etc? i.e. its a string which matches FILE *fdopen(int fd, const char *mode); so mode makes sense to me.

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@kleisauke kleisauke Apr 1, 2026

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I tried to follow Node.js conventions here:
https://nodejs.org/api/fs.html#fsopensyncpath-flags-mode

At first, I wondered "Why is mode being passed to flags?" and made this change to prevent that confusion.

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@sbc100 sbc100 Apr 1, 2026

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Ok.. well thats confusing. C calls the r/w/a string things mode.. not flags, but node calls is falgs. I guess maybe worth adding a comment for this.

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@kleisauke kleisauke Apr 3, 2026

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It's a bit confusing indeed. I think it's only a issue with fs.open{sync,}() though, as that accepts flags (which can also be a number) and mode (corresponding to mode_t in native code).

emscripten/system/lib/libc/musl/src/fcntl/open.c

Lines 5 to 16 in 8e4eee8

int open(const char *filename, int flags, ...)
{
mode_t mode = 0;
if ((flags & O_CREAT) || (flags & O_TMPFILE) == O_TMPFILE) {
va_list ap;
va_start(ap, flags);
mode = va_arg(ap, mode_t);
va_end(ap);
}
int fd = __sys_open_cp(filename, flags, mode);

As possible follow-up, perhaps we could do?:

Suggested change
[[nodiscard]] int _wasmfs_node_open(const char* path, const char* flags);
[[nodiscard]] int _wasmfs_node_open(const char* path, int flags);

That would make it less confusing, as it would align with POSIX open(2) (and would avoid the need of UTF8ToString()).

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@kleisauke kleisauke Apr 3, 2026

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... actually, we can't change const char* flags to int flags as Node.js's fs.constants are derived from the underlying file system constants, which can vary.


// Close the underlying file descriptor.
[[nodiscard]] int _wasmfs_node_close(int fd);
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