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Recover from bad redirections in the middle of a job pipeline

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Currently fish aborts execution mid-pipeline if a file redirection
failed, which can leave the shell in a broken state (job abandoned after
giving control of the terminal to an already-executed job in the
pipeline).

This patch replaces a failed fd with a closed fd and continues execution
if the affected process wasn't the first in the pipeline.

While this is a hack to address the regression behind fish-shell/#7038
introduced in d62576c, it can also be argued that this behavior is
actually more correct... right?

Closes #7038.
This commit is contained in:
Mahmoud Al-Qudsi
2020-05-29 23:54:42 -05:00
parent 4785440f65
commit bc756a981e
3 changed files with 21 additions and 5 deletions
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18
src/exec.cpp
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@@ -745,8 +745,8 @@ static bool exec_block_or_func_process(parser_t &parser, const std::shared_ptr<j
return true;
}
/// Executes a process \p in job \j, using the pipes \p pipes (which may have invalid fds if this is
/// the first or last process).
/// Executes a process \p \p in \p job, using the pipes \p pipes (which may have invalid fds if this
/// is the first or last process).
/// \p deferred_pipes represents the pipes from our deferred process; if set ensure they get closed
/// in any child. If \p is_deferred_run is true, then this is a deferred run; this affects how
/// certain buffering works. \returns true on success, false on exec error.
@@ -800,8 +800,18 @@ static bool exec_process_in_job(parser_t &parser, process_t *p, const std::share
// This may fail.
if (!process_net_io_chain.append_from_specs(p->redirection_specs(),
parser.vars().get_pwd_slash())) {
// Error.
return false;
// If the redirection to a file failed, append_from_specs closes the corresponding handle
// allowing us to recover from failure mid-way through execution of a piped job to e.g.
// recover from loss of terminal control, etc.
// It is unsafe to abort execution in the middle of a multi-command job as we might end up
// trying to resume execution without control of the terminal.
if (p->is_first_in_job) {
// It's OK to abort here
return false;
}
// Otherwise, just rely on the closed fd to take care of things. It's also probably more
// semantically correct!
}
// Read pipe goes last.