diff options
Diffstat (limited to 'butl/fdstream')
| -rw-r--r-- | butl/fdstream | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/butl/fdstream b/butl/fdstream index 8d01b2f..8d6385f 100644 --- a/butl/fdstream +++ b/butl/fdstream @@ -486,6 +486,9 @@ namespace butl // process' umask, so effective permissions are permissions & ~umask. On // Windows permissions other than ru and wu are unlikelly to have effect. // + // Also note that on POSIX the FD_CLOEXEC flag is set for the file descriptor + // to prevent its leakage into child processes. + // LIBBUTL_EXPORT auto_fd fdopen (const char*, fdopen_mode, @@ -510,6 +513,13 @@ namespace butl // Duplicate an open file descriptor. Throw ios::failure on the underlying // OS error. // + // Note that on POSIX the FD_CLOEXEC flag is set for the new descriptor if it + // is present for the source one. That's in contrast to POSIX dup() that + // doesn't copy file descriptor flags. Also note that duplicating descriptor + // and setting the flag is not an atomic operation. + // + // @@ Should we copy HANDLE_FLAG_INHERIT flag on Windows as well? + // LIBBUTL_EXPORT auto_fd fddup (int fd); @@ -563,6 +573,9 @@ namespace butl // closed. One difference, however, would be if you were to both write to // and read from the descriptor. // + // Note that on POSIX the FD_CLOEXEC flag is set for the file descriptor to + // prevent its leakage into child processes. + // // @@ You may have noticed that this interface doesn't match fdopen() (it // does not throw and return int instead of auto_fd). The reason for this // is process and its need to translate everything to process_error). @@ -591,6 +604,13 @@ namespace butl // In particular, the process class that uses fdpipe underneath makes the // appropriate end of pipe (the one being passed to the child) inheritable. // + // Note that on POSIX the FD_CLOEXEC flag is set for both ends, so they get + // automatically closed by the child process to prevent undesired behaviors + // (such as child deadlock on read from a pipe due to the write-end leakage + // into the child process). Opening pipe and setting the flag is not an + // atomic operation. Also note that you don't need to reset the flag for a + // pipe end being passed to the process class ctor. + // LIBBUTL_EXPORT fdpipe fdopen_pipe (fdopen_mode = fdopen_mode::none); } |