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Use global POSIX shm names #117

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Merged
dallison merged 2 commits into from
Jul 21, 2026
Merged

Use global POSIX shm names #117

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5d491f0
Use global POSIX shm names
dallison Jul 21, 2026
36c4189
Use global POSIX shm names in Rust
dallison Jul 21, 2026
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9 changes: 8 additions & 1 deletion common/channel.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -401,7 +401,14 @@ Channel::PosixSharedMemoryName(const std::string &shadow_file) {
// Use the inode number (unique per file) to make the shm file name.
// st_ino is unsigned and can be 64-bit on some systems (e.g. QNX), so
// promote to uint64_t before formatting.
return absl::StrFormat("subspace_%llu",
//
// The leading '/' is required: POSIX shm_open names that do not start with
// '/' are implementation-defined. On QNX they resolve relative to the
// process cwd, so a publisher started under
// /applications/install/opt/<App>/ creates objects that a subscriber
// started from '/' cannot open (ENOENT). A leading slash places the object
// in the global shm namespace (macOS also requires a leading '/').
return absl::StrFormat("/subspace_%llu",
static_cast<unsigned long long>(st.st_ino));
}
#endif
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4 changes: 3 additions & 1 deletion rust_client/src/publisher.rs
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Expand Up @@ -880,7 +880,9 @@ fn create_shm(name: &str, size: usize) -> crate::error::Result<RawFd> {
#[cfg(not(target_os = "linux"))]
fn posix_shm_name(shadow_path: &str) -> crate::error::Result<String> {
let stat = crate::syscall_shim::shim_stat(shadow_path)?;
Ok(format!("subspace_{}", stat.st_ino))
// POSIX shm names must use the global namespace so Rust and C++ clients
// resolve the same object even when their working directories differ.
Ok(format!("/subspace_{}", stat.st_ino))
}

#[cfg(not(target_os = "linux"))]
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