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Share file offset across processes

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This change ensures that if a file descriptor for an open disk file gets
shared by multiple processes within a process tree, then lseek() changes
will be visible across processes, and read() / write() are synchronized.
Note this only applies to Windows, because UNIX kernels already do this.
This commit is contained in:
Justine Tunney 2024-08-03 01:24:46 -07:00
parent a80ab3f8fe
commit 761c6ad615
No known key found for this signature in database
GPG key ID: BE714B4575D6E328
15 changed files with 256 additions and 63 deletions
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5
libc/calls/open-nt.c
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@ -138,6 +138,7 @@ static textwindows int sys_open_nt_file(int dirfd, const char *file,
int64_t handle;
if ((handle = sys_open_nt_impl(dirfd, file, flags, mode,
kNtFileFlagOverlapped)) != -1) {
g_fds.p[fd].shared = __cursor_new();
g_fds.p[fd].handle = handle;
g_fds.p[fd].kind = kFdFile;
g_fds.p[fd].flags = flags;
@ -170,14 +171,14 @@ static textwindows int sys_open_nt_no_handle(int fd, int flags, int mode,
static textwindows int sys_open_nt_dup(int fd, int flags, int mode, int oldfd) {
int64_t handle;
if (!__isfdopen(oldfd)) {
if (!__isfdopen(oldfd))
return enoent();
}
if (DuplicateHandle(GetCurrentProcess(), g_fds.p[oldfd].handle,
GetCurrentProcess(), &handle, 0, true,
kNtDuplicateSameAccess)) {
g_fds.p[fd] = g_fds.p[oldfd];
g_fds.p[fd].handle = handle;
g_fds.p[fd].isdup = true;
g_fds.p[fd].mode = mode;
if (!sys_fcntl_nt_setfl(fd, flags)) {
return fd;