github-mirror/fish-shell
2
0
Fork 0
mirror of https://github.com/fish-shell/fish-shell.git synced 2024-12-13 01:03:47 +08:00
Code Issues Actions 2 Packages Projects Releases Wiki Activity
1c8093fc50
fish-shell/src/exec.cpp
ridiculousfish 1c8093fc50 Bravely remove the "temporary backgrounding" code 
Prior to this commit, when executing a builtin, we mark the job as not
foreground. After this commit we no longer modify the foreground state
of the job just for the builtin.

There was the following comment:

    // Since this may be the foreground job, and since a builtin may execute another
    // foreground job, we need to pretend to suspend this job while running the
    // builtin, in order to avoid a situation where two jobs are running at once.

The concern seemed to be in the `bg` and `fg` builtins, which might attempt
to foreground or background the jobs associated with `bg` and `fg` themselves.
But the builtins run before the job is marked constructed, so it cannot
actually happen.

Bravely remove this code.
2020-02-19 18:25:36 -07:00

1126 lines
46 KiB
C++
Raw Blame History

// Functions for executing a program.
//
// Some of the code in this file is based on code from the Glibc manual, though the changes
// performed have been massive.
#include "config.h"
#include <errno.h>
#include <fcntl.h>
#ifdef HAVE_SIGINFO_H
#include <siginfo.h>
#endif
#include <signal.h>
#ifdef HAVE_SPAWN_H
#include <spawn.h>
#endif
#include <stdio.h>
#include <sys/wait.h>
#include <unistd.h>
#include <algorithm>
#include <cstring>
#include <functional>
#include <map>
#include <memory>
#include <stack>
#include <string>
#include <type_traits>
#include <vector>
#include "builtin.h"
#include "common.h"
#include "env.h"
#include "exec.h"
#include "fallback.h" // IWYU pragma: keep
#include "flog.h"
#include "function.h"
#include "io.h"
#include "iothread.h"
#include "null_terminated_array.h"
#include "parse_tree.h"
#include "parser.h"
#include "path.h"
#include "postfork.h"
#include "proc.h"
#include "reader.h"
#include "redirection.h"
#include "signal.h"
#include "timer.h"
#include "trace.h"
#include "wutil.h" // IWYU pragma: keep
/// Number of calls to fork() or posix_spawn().
static relaxed_atomic_t<int> s_fork_count{0};
pgroup_provenance_t get_pgroup_provenance(const shared_ptr<job_t> &j,
const job_lineage_t &lineage) {
bool first_proc_is_internal = j->processes.front()->is_internal();
bool has_internal = j->has_internal_proc();
bool has_external = j->has_external_proc();
assert(first_proc_is_internal ? has_internal : has_external);
if (lineage.parent_pgid.has_value()) {
// Our lineage indicates a pgid. This means the job is "nested" as a function or block
// inside another job, which has a real pgroup. We're going to use that.
return pgroup_provenance_t::lineage;
} else if (!j->wants_job_control()) {
// This job doesn't need job control, it can just live in the fish pgroup.
return pgroup_provenance_t::fish_itself;
} else if (has_external && !first_proc_is_internal) {
// The first process is external, it will own the pgroup.
return pgroup_provenance_t::first_external_proc;
} else if (has_external && first_proc_is_internal) {
// The terminal owner has to be the process which is permitted to read from stdin.
// This is the first process in the pipeline. When executing, a process in the job will
// claim the pgrp if it's not set; therefore set it according to the first process.
// Only do this if there's an external process - see #6011.
return pgroup_provenance_t::fish_itself;
} else {
assert(has_internal && !has_external && "Should be internal only");
// This job consists of only internal functions or builtins; we do not need to assign a
// pgroup (yet).
return pgroup_provenance_t::unassigned;
}
}
/// This function is executed by the child process created by a call to fork(). It should be called
/// after \c child_setup_process. It calls execve to replace the fish process image with the command
/// specified in \c p. It never returns. Called in a forked child! Do not allocate memory, etc.
static void safe_launch_process(process_t *p, const char *actual_cmd, const char *const *cargv,
const char *const *cenvv) {
UNUSED(p);
int err;
// This function never returns, so we take certain liberties with constness.
char *const *envv = const_cast<char *const *>(cenvv);
char *const *argv = const_cast<char *const *>(cargv);
execve(actual_cmd, argv, envv);
err = errno;
// Something went wrong with execve, check for a ":", and run /bin/sh if encountered. This is a
// weird predecessor to the shebang that is still sometimes used since it is supported on
// Windows. OK to not use CLO_EXEC here because this is called after fork and the file is
// immediately closed.
int fd = open(actual_cmd, O_RDONLY);
if (fd >= 0) {
char begin[1] = {0};
ssize_t amt_read = read(fd, begin, 1);
close(fd);
if ((amt_read == 1) && (begin[0] == ':')) {
// Relaunch it with /bin/sh. Don't allocate memory, so if you have more args than this,
// update your silly script! Maybe this should be changed to be based on ARG_MAX
// somehow.
char sh_command[] = "/bin/sh";
char *argv2[128];
argv2[0] = sh_command;
for (size_t i = 1; i < sizeof argv2 / sizeof *argv2; i++) {
argv2[i] = argv[i - 1];
if (argv2[i] == nullptr) break;
}
execve(sh_command, argv2, envv);
}
}
errno = err;
safe_report_exec_error(errno, actual_cmd, argv, envv);
exit_without_destructors(STATUS_EXEC_FAIL);
}
/// This function is similar to launch_process, except it is not called after a fork (i.e. it only
/// calls exec) and therefore it can allocate memory.
static void launch_process_nofork(env_stack_t &vars, process_t *p) {
ASSERT_IS_MAIN_THREAD();
ASSERT_IS_NOT_FORKED_CHILD();
null_terminated_array_t<char> argv_array;
convert_wide_array_to_narrow(p->get_argv_array(), &argv_array);
auto export_vars = vars.export_arr();
const char *const *envv = export_vars->get();
char *actual_cmd = wcs2str(p->actual_cmd);
// Ensure the terminal modes are what they were before we changed them.
restore_term_mode();
// Bounce to launch_process. This never returns.
safe_launch_process(p, actual_cmd, argv_array.get(), envv);
}
// Returns whether we can use posix spawn for a given process in a given job.
//
// To avoid the race between the caller calling tcsetpgrp() and the client checking the
// foreground process group, we don't use posix_spawn if we're going to foreground the process. (If
// we use fork(), we can call tcsetpgrp after the fork, before the exec, and avoid the race).
static bool can_use_posix_spawn_for_job(const std::shared_ptr<job_t> &job,
const dup2_list_t &dup2s) {
// Hack - do not use posix_spawn if there are self-fd redirections.
// For example if you were to write:
// cmd 6< /dev/null
// it is possible that the open() of /dev/null would result in fd 6. Here even if we attempted
// to add a dup2 action, it would be ignored and the CLO_EXEC bit would remain. So don't use
// posix_spawn in this case; instead we'll call fork() and clear the CLO_EXEC bit manually.
for (const auto &action : dup2s.get_actions()) {
if (action.src == action.target) return false;
}
if (job->wants_job_control()) { //!OCLINT(collapsible if statements)
// We are going to use job control; therefore when we launch this job it will get its own
// process group ID. But will it be foregrounded?
if (job->should_claim_terminal()) {
// It will be foregrounded, so we will call tcsetpgrp(), therefore do not use
// posix_spawn.
return false;
}
}
return true;
}
static void internal_exec(env_stack_t &vars, job_t *j, const io_chain_t &block_io) {
// Do a regular launch - but without forking first...
process_t *p = j->processes.front().get();
io_chain_t all_ios = block_io;
if (!all_ios.append_from_specs(p->redirection_specs(), vars.get_pwd_slash())) {
return;
}
// child_setup_process makes sure signals are properly set up.
dup2_list_t redirs = dup2_list_t::resolve_chain(all_ios);
if (child_setup_process(INVALID_PID, false, redirs) == 0) {
// Decrement SHLVL as we're removing ourselves from the shell "stack".
auto shlvl_var = vars.get(L"SHLVL", ENV_GLOBAL | ENV_EXPORT);
wcstring shlvl_str = L"0";
if (shlvl_var) {
long shlvl = fish_wcstol(shlvl_var->as_string().c_str());
if (!errno && shlvl > 0) {
shlvl_str = to_string(shlvl - 1);
}
}
vars.set_one(L"SHLVL", ENV_GLOBAL | ENV_EXPORT, std::move(shlvl_str));
// launch_process _never_ returns.
launch_process_nofork(vars, p);
}
}
/// If our pgroup assignment mode wants us to use the first external proc, then apply it here.
static void maybe_assign_pgid_from_child(const std::shared_ptr<job_t> &j, pid_t child_pid) {
// If our assignment mode is the first process, then assign it.
if (j->pgid == INVALID_PID &&
j->pgroup_provenance == pgroup_provenance_t::first_external_proc) {
j->pgid = child_pid;
}
}
/// Construct an internal process for the process p. In the background, write the data \p outdata to
/// stdout and \p errdata to stderr, respecting the io chain \p ios. For example if target_fd is 1
/// (stdout), and there is a dup2 3->1, then we need to write to fd 3. Then exit the internal
/// process.
static void run_internal_process(process_t *p, std::string &&outdata, std::string &&errdata,
const io_chain_t &ios) {
p->check_generations_before_launch();
// We want both the dup2s and the io_chain_ts to be kept alive by the background thread, because
// they may own an fd that we want to write to. Move them all to a shared_ptr. The strings as
// well (they may be long).
// Construct a little helper struct to make it simpler to move into our closure without copying.
struct write_fields_t {
int src_outfd{-1};
std::string outdata{};
int src_errfd{-1};
std::string errdata{};
io_chain_t ios{};
maybe_t<dup2_list_t> dup2s{};
std::shared_ptr<internal_proc_t> internal_proc{};
proc_status_t success_status{};
bool skip_out() const { return outdata.empty() || src_outfd < 0; }
bool skip_err() const { return errdata.empty() || src_errfd < 0; }
};
auto f = std::make_shared<write_fields_t>();
f->outdata = std::move(outdata);
f->errdata = std::move(errdata);
// Construct and assign the internal process to the real process.
p->internal_proc_ = std::make_shared<internal_proc_t>();
f->internal_proc = p->internal_proc_;
FLOGF(proc_internal_proc, L"Created internal proc %llu to write output for proc '%ls'",
p->internal_proc_->get_id(), p->argv0());
// Resolve the IO chain.
// Note it's important we do this even if we have no out or err data, because we may have been
// asked to truncate a file (e.g. `echo -n '' > /tmp/truncateme.txt'). The open() in the dup2
// list resolution will ensure this happens.
f->dup2s = dup2_list_t::resolve_chain(ios);
// Figure out which source fds to write to. If they are closed (unlikely) we just exit
// successfully.
f->src_outfd = f->dup2s->fd_for_target_fd(STDOUT_FILENO);
f->src_errfd = f->dup2s->fd_for_target_fd(STDERR_FILENO);
// If we have nothing to write we can elide the thread.
// TODO: support eliding output to /dev/null.
if (f->skip_out() && f->skip_err()) {
f->internal_proc->mark_exited(p->status);
return;
}
// Ensure that ios stays alive, it may own fds.
f->ios = ios;
// If our process is a builtin, it will have already set its status value. Make sure we
// propagate that if our I/O succeeds and don't read it on a background thread. TODO: have
// builtin_run provide this directly, rather than setting it in the process.
f->success_status = p->status;
iothread_perform_cantwait([f]() {
proc_status_t status = f->success_status;
if (!f->skip_out()) {
ssize_t ret = write_loop(f->src_outfd, f->outdata.data(), f->outdata.size());
if (ret < 0) {
if (errno != EPIPE) {
wperror(L"write");
}
if (status.is_success()) {
status = proc_status_t::from_exit_code(1);
}
}
}
if (!f->skip_err()) {
ssize_t ret = write_loop(f->src_errfd, f->errdata.data(), f->errdata.size());
if (ret < 0) {
if (errno != EPIPE) {
wperror(L"write");
}
if (status.is_success()) {
status = proc_status_t::from_exit_code(1);
}
}
}
f->internal_proc->mark_exited(status);
});
}
/// If \p outdata or \p errdata are both empty, then mark the process as completed immediately.
/// Otherwise, run an internal process.
static void run_internal_process_or_short_circuit(parser_t &parser, const std::shared_ptr<job_t> &j,
process_t *p, std::string &&outdata,
std::string &&errdata, const io_chain_t &ios) {
if (outdata.empty() && errdata.empty()) {
p->completed = true;
if (p->is_last_in_job) {
FLOGF(exec_job_status, L"Set status of job %d (%ls) to %d using short circuit",
j->job_id(), j->preview().c_str(), p->status);
parser.set_last_statuses(j->get_statuses());
}
} else {
run_internal_process(p, std::move(outdata), std::move(errdata), ios);
}
}
/// Call fork() as part of executing a process \p p in a job \j. Execute \p child_action in the
/// context of the child. Returns true if fork succeeded, false if fork failed.
static bool fork_child_for_process(const std::shared_ptr<job_t> &job, process_t *p,
const dup2_list_t &dup2s, const char *fork_type,
const std::function<void()> &child_action) {
pid_t pid = execute_fork();
if (pid == 0) {
// This is the child process. Setup redirections, print correct output to
// stdout and stderr, and then exit.
maybe_t<pid_t> new_termowner{};
p->pid = getpid();
child_set_group(job.get(), p);
child_setup_process(job->should_claim_terminal() ? job->pgid : INVALID_PID, true, dup2s);
child_action();
DIE("Child process returned control to fork_child lambda!");
}
if (pid < 0) {
FLOGF(warning, L"Failed to fork %s!\n", fork_type);
job_mark_process_as_failed(job, p);
return false;
}
// This is the parent process. Store away information on the child, and
// possibly give it control over the terminal.
s_fork_count++;
FLOGF(exec_fork, L"Fork #%d, pid %d: %s for '%ls'", int(s_fork_count), pid, fork_type,
p->argv0());
p->pid = pid;
maybe_assign_pgid_from_child(job, p->pid);
set_child_group(job.get(), p->pid);
terminal_maybe_give_to_job(job.get(), false);
return true;
}
/// Execute an internal builtin. Given a parser and a builtin process, execute the builtin with the
/// given streams. If pipe_read is set, assign stdin to it; otherwise infer stdin from the IO chain.
/// \return true on success, false if there is an exec error.
static bool exec_internal_builtin_proc(parser_t &parser, process_t *p, const io_pipe_t *pipe_read,
const io_chain_t &proc_io_chain, io_streams_t &streams) {
assert(p->type == process_type_t::builtin && "Process must be a builtin");
int local_builtin_stdin = STDIN_FILENO;
autoclose_fd_t locally_opened_stdin{};
// If this is the first process, check the io redirections and see where we should
// be reading from.
if (pipe_read) {
local_builtin_stdin = pipe_read->source_fd;
} else if (const auto in = proc_io_chain.io_for_fd(STDIN_FILENO)) {
// Ignore fd redirections from an fd other than the
// standard ones. e.g. in source <&3 don't actually read from fd 3,
// which is internal to fish. We still respect this redirection in
// that we pass it on as a block IO to the code that source runs,
// and therefore this is not an error.
bool ignore_redirect =
in->io_mode == io_mode_t::fd && in->source_fd >= 0 && in->source_fd < 3;
if (!ignore_redirect) {
local_builtin_stdin = in->source_fd;
}
}
if (local_builtin_stdin == -1) return false;
// Determine if we have a "direct" redirection for stdin.
bool stdin_is_directly_redirected = false;
if (!p->is_first_in_job) {
// We must have a pipe
stdin_is_directly_redirected = true;
} else {
// We are not a pipe. Check if there is a redirection local to the process
// that's not io_mode_t::close.
for (const auto &redir : p->redirection_specs()) {
if (redir.fd == STDIN_FILENO && !redir.is_close()) {
stdin_is_directly_redirected = true;
break;
}
}
}
streams.stdin_fd = local_builtin_stdin;
streams.out_is_redirected = proc_io_chain.io_for_fd(STDOUT_FILENO) != nullptr;
streams.err_is_redirected = proc_io_chain.io_for_fd(STDERR_FILENO) != nullptr;
streams.stdin_is_directly_redirected = stdin_is_directly_redirected;
streams.io_chain = &proc_io_chain;
// Note this call may block for a long time, while the builtin performs I/O.
p->status = builtin_run(parser, p->get_argv(), streams);
return true; // "success"
}
/// Handle output from a builtin, by printing the contents of builtin_io_streams to the redirections
/// given in io_chain.
static bool handle_builtin_output(parser_t &parser, const std::shared_ptr<job_t> &j, process_t *p,
io_chain_t *io_chain, const io_streams_t &builtin_io_streams) {
assert(p->type == process_type_t::builtin && "Process is not a builtin");
const output_stream_t &stdout_stream = builtin_io_streams.out;
const output_stream_t &stderr_stream = builtin_io_streams.err;
// Mark if we discarded output.
if (stdout_stream.buffer().discarded()) {
p->status = proc_status_t::from_exit_code(STATUS_READ_TOO_MUCH);
}
const shared_ptr<const io_data_t> stdout_io = io_chain->io_for_fd(STDOUT_FILENO);
const shared_ptr<const io_data_t> stderr_io = io_chain->io_for_fd(STDERR_FILENO);
// If we are directing output to a buffer, then we can just transfer it directly without needing
// to write to the bufferfill pipe. Note this is how we handle explicitly separated stdout
// output (i.e. string split0) which can't really be sent through a pipe.
// TODO: we're sloppy about handling explicitly separated output.
// Theoretically we could have explicitly separated output on stdout and also stderr output; in
// that case we ought to thread the exp-sep output through to the io buffer. We're getting away
// with this because the only thing that can output exp-sep output is `string split0` which
// doesn't also produce stderr. Also note that we never send stderr to a buffer, so there's no
// need for a similar check for stderr.
bool stdout_done = false;
if (stdout_io && stdout_io->io_mode == io_mode_t::bufferfill) {
auto stdout_buffer = static_cast<const io_bufferfill_t *>(stdout_io.get())->buffer();
stdout_buffer->append_from_stream(stdout_stream);
stdout_done = true;
}
// Figure out any data remaining to write. We may have none in which case we can short-circuit.
std::string outbuff = stdout_done ? std::string{} : wcs2string(stdout_stream.contents());
std::string errbuff = wcs2string(stderr_stream.contents());
// If we have no redirections for stdout/stderr, just write them directly.
if (!stdout_io && !stderr_io) {
bool did_err = false;
if (write_loop(STDOUT_FILENO, outbuff.data(), outbuff.size()) < 0) {
if (errno != EPIPE) {
did_err = true;
FLOG(error, L"Error while writing to stdout");
wperror(L"write_loop");
}
}
if (write_loop(STDERR_FILENO, errbuff.data(), errbuff.size()) < 0) {
if (errno != EPIPE && !did_err) {
did_err = true;
FLOG(error, L"Error while writing to stderr");
wperror(L"write_loop");
}
}
if (did_err) {
redirect_tty_output(); // workaround glibc bug
FLOG(error, L"!builtin_io_done and errno != EPIPE");
show_stackframe(L'E');
}
// Clear the buffers to indicate we finished.
outbuff.clear();
errbuff.clear();
}
// Some historical behavior.
if (!outbuff.empty()) fflush(stdout);
if (!errbuff.empty()) fflush(stderr);
// Construct and run our background process.
run_internal_process_or_short_circuit(parser, j, p, std::move(outbuff), std::move(errbuff),
*io_chain);
return true;
}
/// Executes an external command.
/// \return true on success, false if there is an exec error.
static bool exec_external_command(parser_t &parser, const std::shared_ptr<job_t> &j, process_t *p,
const io_chain_t &proc_io_chain) {
assert(p->type == process_type_t::external && "Process is not external");
// Get argv and envv before we fork.
null_terminated_array_t<char> argv_array;
convert_wide_array_to_narrow(p->get_argv_array(), &argv_array);
// Convert our IO chain to a dup2 sequence.
auto dup2s = dup2_list_t::resolve_chain(proc_io_chain);
// Ensure that stdin is blocking before we hand it off (see issue #176). It's a
// little strange that we only do this with stdin and not with stdout or stderr.
// However in practice, setting or clearing O_NONBLOCK on stdin also sets it for the
// other two fds, presumably because they refer to the same underlying file
// (/dev/tty?).
make_fd_blocking(STDIN_FILENO);
auto export_arr = parser.vars().export_arr();
const char *const *argv = argv_array.get();
const char *const *envv = export_arr->get();
std::string actual_cmd_str = wcs2string(p->actual_cmd);
const char *actual_cmd = actual_cmd_str.c_str();
const wchar_t *file = parser.libdata().current_filename;
#if FISH_USE_POSIX_SPAWN
// Prefer to use posix_spawn, since it's faster on some systems like OS X.
bool use_posix_spawn = g_use_posix_spawn && can_use_posix_spawn_for_job(j, dup2s);
if (use_posix_spawn) {
s_fork_count++; // spawn counts as a fork+exec
// Create posix spawn attributes and actions.
pid_t pid = 0;
posix_spawnattr_t attr = posix_spawnattr_t();
posix_spawn_file_actions_t actions = posix_spawn_file_actions_t();
bool made_it = fork_actions_make_spawn_properties(&attr, &actions, j.get(), dup2s);
if (made_it) {
// We successfully made the attributes and actions; actually call
// posix_spawn.
int spawn_ret =
posix_spawn(&pid, actual_cmd, &actions, &attr, const_cast<char *const *>(argv),
const_cast<char *const *>(envv));
// This usleep can be used to test for various race conditions
// (https://github.com/fish-shell/fish-shell/issues/360).
// usleep(10000);
if (spawn_ret != 0) {
safe_report_exec_error(spawn_ret, actual_cmd, argv, envv);
// Make sure our pid isn't set.
pid = 0;
}
// Clean up our actions.
posix_spawn_file_actions_destroy(&actions);
posix_spawnattr_destroy(&attr);
}
// A 0 pid means we failed to posix_spawn. Since we have no pid, we'll never get
// told when it's exited, so we have to mark the process as failed.
FLOGF(exec_fork, L"Fork #%d, pid %d: spawn external command '%s' from '%ls'",
int(s_fork_count), pid, actual_cmd, file ? file : L"<no file>");
if (pid == 0) {
job_mark_process_as_failed(j, p);
return false;
}
// these are all things do_fork() takes care of normally (for forked processes):
p->pid = pid;
maybe_assign_pgid_from_child(j, p->pid);
// In glibc, posix_spawn uses fork() and the pgid group is set on the child side;
// therefore the parent may not have seen it be set yet.
// Ensure it gets set. See #4715, also https://github.com/Microsoft/WSL/issues/2997.
set_child_group(j.get(), p->pid);
terminal_maybe_give_to_job(j.get(), false);
} else
#endif
{
if (!fork_child_for_process(j, p, dup2s, "external command",
[&] { safe_launch_process(p, actual_cmd, argv, envv); })) {
return false;
}
}
return true;
}
// Given that we are about to execute a function, push a function block and set up the
// variable environment.
static block_t *function_prepare_environment(parser_t &parser, wcstring_list_t argv,
const function_properties_t &props) {
// Extract the function name and remaining arguments.
wcstring func_name;
if (!argv.empty()) {
// Extract and remove the function name from argv.
func_name = std::move(*argv.begin());
argv.erase(argv.begin());
}
block_t *fb = parser.push_block(block_t::function_block(func_name, argv, props.shadow_scope));
auto &vars = parser.vars();
// Setup the environment for the function. There are three components of the environment:
// 1. named arguments
// 2. inherited variables
// 3. argv
size_t idx = 0;
for (const wcstring &named_arg : props.named_arguments) {
if (idx < argv.size()) {
vars.set_one(named_arg, ENV_LOCAL | ENV_USER, argv.at(idx));
} else {
vars.set_empty(named_arg, ENV_LOCAL | ENV_USER);
}
idx++;
}
for (const auto &kv : props.inherit_vars) {
vars.set(kv.first, ENV_LOCAL | ENV_USER, kv.second);
}
vars.set_argv(std::move(argv));
return fb;
}
// Given that we are done executing a function, restore the environment.
static void function_restore_environment(parser_t &parser, const block_t *block) {
parser.pop_block(block);
// If we returned due to a return statement, then stop returning now.
parser.libdata().returning = false;
}
// The "performer" function of a block or function process.
// This accepts a place to execute as \p parser, and a parent job as \p parent, and then executes
// the result, returning a status.
// This is factored out in this funny way in preparation for concurrent execution.
using proc_performer_t = std::function<proc_status_t(parser_t &parser)>;
// \return a function which may be to run the given process \p.
// May return an empty std::function in the rare case that the to-be called fish function no longer
// exists. This is just a dumb artifact of the fact that we only capture the functions name, not its
// properties, when creating the job; thus a race could delete the function before we fetch its
// properties.
static proc_performer_t get_performer_for_process(process_t *p, job_t *job,
const io_chain_t &io_chain) {
assert((p->type == process_type_t::function || p->type == process_type_t::block_node) &&
"Unexpected process type");
// Make a lineage for our children.
job_lineage_t lineage;
lineage.parent_pgid = (job->pgid == INVALID_PID ? none() : maybe_t<pid_t>(job->pgid));
lineage.block_io = io_chain;
lineage.root_constructed = job->root_constructed;
lineage.root_has_job_control = job->wants_job_control();
if (p->type == process_type_t::block_node) {
const parsed_source_ref_t &source = p->block_node_source;
tnode_t<grammar::statement> node = p->internal_block_node;
assert(source && node && "Process is missing node info");
return [=](parser_t &parser) { return parser.eval_node(source, node, lineage).status; };
} else {
assert(p->type == process_type_t::function);
auto props = function_get_properties(p->argv0());
if (!props) {
FLOGF(error, _(L"Unknown function '%ls'"), p->argv0());
return proc_performer_t{};
}
auto argv = move_to_sharedptr(p->get_argv_array().to_list());
return [=](parser_t &parser) {
// Pull out the job list from the function.
tnode_t<grammar::job_list> body = props->func_node.child<1>();
const block_t *fb = function_prepare_environment(parser, *argv, *props);
auto res = parser.eval_node(props->parsed_source, body, lineage);
function_restore_environment(parser, fb);
// If the function did not execute anything, treat it as success.
if (res.was_empty) {
res = proc_status_t::from_exit_code(EXIT_SUCCESS);
}
return res.status;
};
}
}
/// Execute a block node or function "process".
/// \p conflicts contains the list of fds which pipes should avoid.
/// \p allow_buffering if true, permit buffering the output.
/// \return true on success, false on error.
static bool exec_block_or_func_process(parser_t &parser, const std::shared_ptr<job_t> &j,
process_t *p, const fd_set_t &conflicts, io_chain_t io_chain,
bool allow_buffering) {
// Create an output buffer if we're piping to another process.
shared_ptr<io_bufferfill_t> block_output_bufferfill{};
if (!p->is_last_in_job && allow_buffering) {
// Be careful to handle failure, e.g. too many open fds.
block_output_bufferfill = io_bufferfill_t::create(conflicts);
if (!block_output_bufferfill) {
job_mark_process_as_failed(j, p);
return false;
}
// Teach the job about its bufferfill, and add it to our io chain.
io_chain.push_back(block_output_bufferfill);
}
// If this function is the only process in the current job
// and that job is in the foreground then mark this job as internal
// so it doesn't increment the job id for any jobs created within this
// function.
if (p->is_first_in_job && p->is_last_in_job && j->flags().foreground) {
j->mark_internal();
}
// Get the process performer, and just execute it directly.
// Do it in this scoped way so that the performer function can be eagerly deallocating releasing
// its captured io chain.
if (proc_performer_t performer = get_performer_for_process(p, j.get(), io_chain)) {
p->status = performer(parser);
} else {
return false;
}
// If we have a block output buffer, populate it now.
std::string buffer_contents;
if (block_output_bufferfill) {
// Remove our write pipe and forget it. This may close the pipe, unless another thread has
// claimed it (background write) or another process has inherited it.
io_chain.remove(block_output_bufferfill);
auto block_output_buffer = io_bufferfill_t::finish(std::move(block_output_bufferfill));
buffer_contents = block_output_buffer->buffer().newline_serialized();
}
run_internal_process_or_short_circuit(parser, j, p, std::move(buffer_contents),
{} /* errdata */, io_chain);
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).
/// \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.
static bool exec_process_in_job(parser_t &parser, process_t *p, const std::shared_ptr<job_t> &j,
const io_chain_t &block_io, autoclose_pipes_t pipes,
const fd_set_t &conflicts, const autoclose_pipes_t &deferred_pipes,
size_t stdout_read_limit, bool is_deferred_run = false) {
// The write pipe (destined for stdout) needs to occur before redirections. For example,
// with a redirection like this:
//
// `foo 2>&1 | bar`
//
// what we want to happen is this:
//
// dup2(pipe, stdout)
// dup2(stdout, stderr)
//
// so that stdout and stderr both wind up referencing the pipe.
//
// The read pipe (destined for stdin) is more ambiguous. Imagine a pipeline like this:
//
// echo alpha | cat < beta.txt
//
// Should cat output alpha or beta? bash and ksh output 'beta', tcsh gets it right and
// complains about ambiguity, and zsh outputs both (!). No shells appear to output 'alpha',
// so we match bash here. That would mean putting the pipe first, so that it gets trumped by
// the file redirection.
//
// However, eval does this:
//
// echo "begin; $argv "\n" ;end <&3 3<&-" | source 3<&0
//
// which depends on the redirection being evaluated before the pipe. So the write end of the
// pipe comes first, the read pipe of the pipe comes last. See issue #966.
// Maybe trace this process.
// TODO: 'and' and 'or' will not show.
if (trace_enabled(parser)) {
trace_argv(parser, nullptr, p->get_argv_array().to_list());
}
// The IO chain for this process.
io_chain_t process_net_io_chain = block_io;
if (pipes.write.valid()) {
process_net_io_chain.push_back(std::make_shared<io_pipe_t>(
p->pipe_write_fd, false /* not input */, std::move(pipes.write)));
}
// Append IOs from the process's redirection specs.
// This may fail.
if (!process_net_io_chain.append_from_specs(p->redirection_specs(),
parser.vars().get_pwd_slash())) {
// Error.
return false;
}
// Read pipe goes last.
shared_ptr<io_pipe_t> pipe_read{};
if (pipes.read.valid()) {
pipe_read =
std::make_shared<io_pipe_t>(STDIN_FILENO, true /* input */, std::move(pipes.read));
process_net_io_chain.push_back(pipe_read);
}
// If we have stashed pipes, make sure those get closed in the child.
for (const autoclose_fd_t *afd : {&deferred_pipes.read, &deferred_pipes.write}) {
if (afd->valid()) {
process_net_io_chain.push_back(std::make_shared<io_close_t>(afd->fd()));
}
}
if (p->type != process_type_t::block_node) {
// A simple `begin ... end` should not be considered an execution of a command.
parser.libdata().exec_count++;
}
const block_t *block = nullptr;
cleanup_t pop_block([&]() {
if (block) parser.pop_block(block);
});
if (!p->variable_assignments.empty()) {
block = parser.push_block(block_t::variable_assignment_block());
}
for (const auto &assignment : p->variable_assignments) {
parser.vars().set(assignment.variable_name, ENV_LOCAL | ENV_EXPORT, assignment.values);
}
// Execute the process.
p->check_generations_before_launch();
switch (p->type) {
case process_type_t::function:
case process_type_t::block_node: {
// Allow buffering unless this is a deferred run. If deferred, then processes after us
// were already launched, so they are ready to receive (or reject) our output.
bool allow_buffering = !is_deferred_run;
if (!exec_block_or_func_process(parser, j, p, conflicts, process_net_io_chain,
allow_buffering)) {
return false;
}
break;
}
case process_type_t::builtin: {
io_streams_t builtin_io_streams{stdout_read_limit};
if (!exec_internal_builtin_proc(parser, p, pipe_read.get(), process_net_io_chain,
builtin_io_streams)) {
return false;
}
if (!handle_builtin_output(parser, j, p, &process_net_io_chain, builtin_io_streams)) {
return false;
}
break;
}
case process_type_t::external: {
if (!exec_external_command(parser, j, p, process_net_io_chain)) {
return false;
}
break;
}
case process_type_t::exec: {
// We should have handled exec up above.
DIE("process_type_t::exec process found in pipeline, where it should never be. "
"Aborting.");
break;
}
}
return true;
}
// Do we have a fish internal process that pipes into a real process? If so, we are going to
// launch it last (if there's more than one, just the last one). That is to prevent buffering
// from blocking further processes. See #1396.
// Example:
// for i in (seq 1 5); sleep 1; echo $i; end | cat
// This should show the output as it comes, not buffer until the end.
// Any such process (only one per job) will be called the "deferred" process.
static process_t *get_deferred_process(const shared_ptr<job_t> &j) {
// By enumerating in reverse order, we can avoid walking the entire list
for (auto i = j->processes.rbegin(); i != j->processes.rend(); ++i) {
const auto &p = *i;
if (p->type == process_type_t::exec) {
// No tail reordering for execs.
return nullptr;
} else if (p->type != process_type_t::external) {
if (p->is_last_in_job) {
return nullptr;
}
return p.get();
}
}
return nullptr;
}
bool exec_job(parser_t &parser, const shared_ptr<job_t> &j, const job_lineage_t &lineage) {
assert(j && "null job_t passed to exec_job!");
// Set to true if something goes wrong while executing the job, in which case the cleanup
// code will kick in.
bool exec_error = false;
// If fish was invoked with -n or --no-execute, then no_exec will be set and we do nothing.
if (no_exec()) {
return true;
}
pid_t pgrp = getpgrp();
// Check to see if we should reclaim the foreground pgrp after the job finishes or stops.
const bool reclaim_foreground_pgrp = (tcgetpgrp(STDIN_FILENO) == pgrp);
// Perhaps we know our pgroup already.
assert(j->pgid == INVALID_PID && "Should not yet have a pid.");
switch (j->pgroup_provenance) {
case pgroup_provenance_t::lineage:
assert(*lineage.parent_pgid != INVALID_PID && "pgid should be none, not INVALID_PID");
j->pgid = *lineage.parent_pgid;
break;
case pgroup_provenance_t::fish_itself:
j->pgid = pgrp;
break;
// The remaining cases are all deferred until later.
case pgroup_provenance_t::unassigned:
case pgroup_provenance_t::first_external_proc:
break;
}
const size_t stdout_read_limit = parser.libdata().read_limit;
// Get the list of all FDs so we can ensure our pipes do not conflict.
fd_set_t conflicts = lineage.block_io.fd_set();
for (const auto &p : j->processes) {
for (const auto &spec : p->redirection_specs()) {
conflicts.add(spec.fd);
}
}
// Handle an exec call.
if (j->processes.front()->type == process_type_t::exec) {
internal_exec(parser.vars(), j.get(), lineage.block_io);
// internal_exec only returns if it failed to set up redirections.
// In case of an successful exec, this code is not reached.
int status = j->flags().negate ? 0 : 1;
parser.set_last_statuses(statuses_t::just(status));
// A false return tells the caller to remove the job from the list.
return false;
}
cleanup_t timer = push_timer(j->flags().has_time_prefix && !no_exec());
// Get the deferred process, if any. We will have to remember its pipes.
autoclose_pipes_t deferred_pipes;
process_t *const deferred_process = get_deferred_process(j);
// This loop loops over every process_t in the job, starting it as appropriate. This turns out
// to be rather complex, since a process_t can be one of many rather different things.
//
// The loop also has to handle pipelining between the jobs.
//
// We can have up to three pipes "in flight" at a time:
//
// 1. The pipe the current process should read from (courtesy of the previous process)
// 2. The pipe that the current process should write to
// 3. The pipe that the next process should read from (courtesy of us)
//
autoclose_fd_t pipe_next_read;
for (const auto &p : j->processes) {
// proc_pipes is the pipes applied to this process. That is, it is the read end
// containing the output of the previous process (if any), plus the write end that will
// output to the next process (if any).
autoclose_pipes_t proc_pipes;
proc_pipes.read = std::move(pipe_next_read);
if (!p->is_last_in_job) {
auto pipes = make_autoclose_pipes(conflicts);
if (!pipes) {
FLOGF(warning, PIPE_ERROR);
wperror(L"pipe");
job_mark_process_as_failed(j, p.get());
exec_error = true;
break;
}
pipe_next_read = std::move(pipes->read);
proc_pipes.write = std::move(pipes->write);
}
if (p.get() == deferred_process) {
deferred_pipes = std::move(proc_pipes);
} else {
if (!exec_process_in_job(parser, p.get(), j, lineage.block_io, std::move(proc_pipes),
conflicts, deferred_pipes, stdout_read_limit)) {
exec_error = true;
break;
}
}
}
pipe_next_read.close();
// Now execute any deferred process.
if (!exec_error && deferred_process) {
assert(deferred_pipes.write.valid() && "Deferred process should always have a write pipe");
if (!exec_process_in_job(parser, deferred_process, j, lineage.block_io,
std::move(deferred_pipes), conflicts, {}, stdout_read_limit,
true)) {
exec_error = true;
}
}
FLOGF(exec_job_exec, L"Executed job %d from command '%ls' with pgrp %d", j->job_id(),
j->command_wcstr(), j->pgid);
j->mark_constructed();
if (!j->is_foreground()) {
parser.vars().set_one(L"last_pid", ENV_GLOBAL, to_string(j->pgid));
}
if (exec_error) {
return false;
}
j->continue_job(parser, reclaim_foreground_pgrp, false);
return true;
}
/// Populate \p lst with the output of \p buffer, perhaps splitting lines according to \p split.
static void populate_subshell_output(wcstring_list_t *lst, const io_buffer_t &buffer, bool split) {
// Walk over all the elements.
for (const auto &elem : buffer.buffer().elements()) {
if (elem.is_explicitly_separated()) {
// Just append this one.
lst->push_back(str2wcstring(elem.contents));
continue;
}
// Not explicitly separated. We have to split it explicitly.
assert(!elem.is_explicitly_separated() && "should not be explicitly separated");
const char *begin = elem.contents.data();
const char *end = begin + elem.contents.size();
if (split) {
const char *cursor = begin;
while (cursor < end) {
// Look for the next separator.
const char *stop =
static_cast<const char *>(std::memchr(cursor, '\n', end - cursor));
const bool hit_separator = (stop != nullptr);
if (!hit_separator) {
// If it's not found, just use the end.
stop = end;
}
// Stop now points at the first character we do not want to copy.
lst->push_back(str2wcstring(cursor, stop - cursor));
// If we hit a separator, skip over it; otherwise we're at the end.
cursor = stop + (hit_separator ? 1 : 0);
}
} else {
// We're not splitting output, but we still want to trim off a trailing newline.
if (end != begin && end[-1] == '\n') {
--end;
}
lst->push_back(str2wcstring(begin, end - begin));
}
}
}
/// Execute \p cmd in a subshell in \p parser. If \p lst is not null, populate it with the output.
/// Return $status in \p out_status.
/// If \p apply_exit_status is false, then reset $status back to its original value.
/// \p is_subcmd controls whether we apply a read limit.
/// \p break_expand is used to propagate whether the result should be "expansion breaking" in the
/// sense that subshells used during string expansion should halt that expansion. \return the value
/// of $status.
static int exec_subshell_internal(const wcstring &cmd, parser_t &parser, wcstring_list_t *lst,
bool *break_expand, bool apply_exit_status, bool is_subcmd) {
ASSERT_IS_MAIN_THREAD();
auto &ld = parser.libdata();
scoped_push<bool> is_subshell(&ld.is_subshell, true);
scoped_push<size_t> read_limit(&ld.read_limit, is_subcmd ? read_byte_limit : 0);
auto prev_statuses = parser.get_last_statuses();
const cleanup_t put_back([&] {
if (!apply_exit_status) {
parser.set_last_statuses(prev_statuses);
}
});
const bool split_output = !parser.vars().get(L"IFS").missing_or_empty();
// IO buffer creation may fail (e.g. if we have too many open files to make a pipe), so this may
// be null.
auto bufferfill = io_bufferfill_t::create(fd_set_t{}, ld.read_limit);
if (!bufferfill) {
*break_expand = true;
return STATUS_CMD_ERROR;
}
eval_res_t eval_res = parser.eval(cmd, io_chain_t{bufferfill}, block_type_t::subst);
std::shared_ptr<io_buffer_t> buffer = io_bufferfill_t::finish(std::move(bufferfill));
if (buffer->buffer().discarded()) {
*break_expand = true;
return STATUS_READ_TOO_MUCH;
}
if (eval_res.break_expand) {
*break_expand = true;
return eval_res.status.status_value();
}
if (lst) {
populate_subshell_output(lst, *buffer, split_output);
}
*break_expand = false;
return eval_res.status.status_value();
}
int exec_subshell_for_expand(const wcstring &cmd, parser_t &parser, wcstring_list_t &outputs) {
ASSERT_IS_MAIN_THREAD();
bool break_expand = false;
int ret = exec_subshell_internal(cmd, parser, &outputs, &break_expand, true, true);
// Only return an error code if we should break expansion.
return break_expand ? ret : STATUS_CMD_OK;
}
int exec_subshell(const wcstring &cmd, parser_t &parser, bool apply_exit_status) {
bool break_expand = false;
return exec_subshell_internal(cmd, parser, nullptr, &break_expand, apply_exit_status, false);
}
int exec_subshell(const wcstring &cmd, parser_t &parser, wcstring_list_t &outputs,
bool apply_exit_status) {
bool break_expand = false;
return exec_subshell_internal(cmd, parser, &outputs, &break_expand, apply_exit_status, false);
}
Reference in New Issue View Git Blame Copy Permalink