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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
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GPG key ID: BE714B4575D6E328
15 changed files with 256 additions and 63 deletions
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9
libc/proc/describefds.c
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@ -17,9 +17,9 @@
│ PERFORMANCE OF THIS SOFTWARE. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/assert.h"
#include "libc/intrin/fds.h"
#include "libc/calls/syscall_support-nt.internal.h"
#include "libc/fmt/itoa.h"
#include "libc/intrin/fds.h"
#include "libc/intrin/strace.h"
#include "libc/mem/mem.h"
#include "libc/nt/files.h"
@ -151,7 +151,12 @@ textwindows char *__describe_fds(const struct Fd *fds, size_t fdslen,
*p++ = '_';
p = FormatInt64(p, f->mode);
*p++ = '_';
p = FormatInt64(p, f->pointer);
//
// - v1 abi: This field was originally the file pointer.
//
// - v2 abi: This field is the negated shared memory address.
//
p = FormatInt64(p, -(uintptr_t)f->shared);
*p++ = '_';
p = FormatInt64(p, f->type);
*p++ = '_';