// Copyright 2010 Google Inc.
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#include "utils/process/child.ipp"
extern "C" {
#include <sys/stat.h>
#include <sys/wait.h>
#include <fcntl.h>
#include <signal.h>
#include <unistd.h>
}
#include <cassert>
#include <cerrno>
#include <cstdlib>
#include <cstring>
#include <iostream>
#include <memory>
#include "utils/defs.hpp"
#include "utils/format/macros.hpp"
#include "utils/logging/macros.hpp"
#include "utils/process/exceptions.hpp"
#include "utils/process/fdstream.hpp"
#include "utils/process/system.hpp"
#include "utils/process/status.hpp"
#include "utils/sanity.hpp"
#include "utils/signals/interrupts.hpp"
namespace utils {
namespace process {
/// Private implementation fields for child objects.
struct child::impl {
/// The process identifier.
pid_t _pid;
/// The input stream for the process' stdout and stderr. May be NULL.
std::auto_ptr< process::ifdstream > _output;
/// Initializes private implementation data.
///
/// \param pid The process identifier.
/// \param output The input stream. Grabs ownership of the pointer.
impl(const pid_t pid, process::ifdstream* output) :
_pid(pid), _output(output) {}
};
} // namespace process
} // namespace utils
namespace fs = utils::fs;
namespace process = utils::process;
namespace signals = utils::signals;
namespace {
/// Exception-based version of dup(2).
///
/// \param old_fd The file descriptor to duplicate.
/// \param new_fd The file descriptor to use as the duplicate. This is
/// closed if it was open before the copy happens.
///
/// \throw process::system_error If the call to dup2(2) fails.
static void
safe_dup(const int old_fd, const int new_fd)
{
if (process::detail::syscall_dup2(old_fd, new_fd) == -1) {
const int original_errno = errno;
throw process::system_error(F("dup2(%s, %s) failed") % old_fd % new_fd,
original_errno);
}
}
/// Exception-based version of open(2) to open (or create) a file for append.
///
/// \param filename The file to open in append mode.
///
/// \return The file descriptor for the opened or created file.
///
/// \throw process::system_error If the call to open(2) fails.
static int
open_for_append(const fs::path& filename)
{
const int fd = process::detail::syscall_open(
filename.c_str(), O_CREAT | O_WRONLY | O_APPEND,
S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
if (fd == -1) {
const int original_errno = errno;
throw process::system_error(F("Failed to create %s because open(2) "
"failed") % filename, original_errno);
}
return fd;
}
/// Exception-based, type-improved version of wait(2).
///
/// Because we are waiting for the termination of a process, and because this is
/// the canonical way to call wait(2) for this module, we ensure from here that
/// any subprocess of the process we are killing is terminated.
///
/// \param pid The identifier of the process to wait for.
///
/// \return The termination status of the process.
///
/// \throw process::system_error If the call to waitpid(2) fails.
static process::status
safe_wait(const pid_t pid)
{
LD(F("Waiting for pid=%s") % pid);
int stat_loc;
if (process::detail::syscall_waitpid(pid, &stat_loc, 0) == -1) {
const int original_errno = errno;
throw process::system_error(F("Failed to wait for PID %s") % pid,
original_errno);
}
return process::status(pid, stat_loc);
}
/// Logs the execution of another program.
///
/// \param program The binary to execute.
/// \param args The arguments to pass to the binary, without the program name.
static void
log_exec(const fs::path& program, const process::args_vector& args)
{
std::string plain_command = program.str();
for (process::args_vector::const_iterator iter = args.begin();
iter != args.end(); ++iter)
plain_command += F(" %s") % *iter;
LD(F("Executing %s") % plain_command);
}
/// Maximum number of arguments supported by cxx_exec.
///
/// We need this limit to avoid having to allocate dynamic memory in the child
/// process to construct the arguments list, which would have side-effects in
/// the parent's memory if we use vfork().
#define MAX_ARGS 128
static void cxx_exec(const fs::path& program, const process::args_vector& args)
throw() UTILS_NORETURN;
/// Executes an external binary and replaces the current process.
///
/// This function must not use any of the logging features, so that the output
/// of the subprocess is not "polluted" by our own messages.
///
/// This function must also not affect the global state of the current process
/// as otherwise we would not be able to use vfork(). Only state stored in the
/// stack can be touched.
///
/// \param program The binary to execute.
/// \param args The arguments to pass to the binary, without the program name.
static void
cxx_exec(const fs::path& program, const process::args_vector& args) throw()
{
assert(args.size() < MAX_ARGS);
try {
const char* argv[MAX_ARGS + 1];
argv[0] = program.c_str();
for (process::args_vector::size_type i = 0; i < args.size(); i++)
argv[1 + i] = args[i].c_str();
argv[1 + args.size()] = NULL;
const int ret = ::execv(program.c_str(),
(char* const*)(unsigned long)(const void*)argv);
const int original_errno = errno;
assert(ret == -1);
std::cerr << "Failed to execute " << program << ": "
<< std::strerror(original_errno) << "\n";
std::abort();
} catch (const std::runtime_error& error) {
std::cerr << "Failed to execute " << program << ": "
<< error.what() << "\n";
std::abort();
} catch (...) {
std::cerr << "Failed to execute " << program << "; got unexpected "
"exception during exec\n";
std::abort();
}
}
} // anonymous namespace
/// Creates a new child.
///
/// \param implptr A dynamically-allocated impl object with the contents of the
/// new child.
process::child::child(impl *implptr) :
_pimpl(implptr)
{
}
/// Destructor for child.
process::child::~child(void)
{
}
/// Helper function for fork().
///
/// Please note: if you update this function to change the return type or to
/// raise different errors, do not forget to update fork() accordingly.
///
/// \return In the case of the parent, a new child object returned as a
/// dynamically-allocated object because children classes are unique and thus
/// noncopyable. In the case of the child, a NULL pointer.
///
/// \throw process::system_error If the calls to pipe(2) or fork(2) fail.
std::auto_ptr< process::child >
process::child::fork_capture_aux(void)
{
std::cout.flush();
std::cerr.flush();
int fds[2];
if (detail::syscall_pipe(fds) == -1)
throw process::system_error("pipe(2) failed", errno);
std::auto_ptr< signals::interrupts_inhibiter > inhibiter(
new signals::interrupts_inhibiter);
pid_t pid = detail::syscall_fork();
if (pid == -1) {
inhibiter.reset(NULL); // Unblock signals.
::close(fds[0]);
::close(fds[1]);
throw process::system_error("fork(2) failed", errno);
} else if (pid == 0) {
inhibiter.reset(NULL); // Unblock signals.
::setpgid(::getpid(), ::getpid());
try {
::close(fds[0]);
safe_dup(fds[1], STDOUT_FILENO);
safe_dup(fds[1], STDERR_FILENO);
::close(fds[1]);
} catch (const system_error& e) {
std::cerr << F("Failed to set up subprocess: %s\n") % e.what();
std::abort();
}
return std::auto_ptr< process::child >(NULL);
} else {
::close(fds[1]);
LD(F("Spawned process %s: stdout and stderr inherited") % pid);
signals::add_pid_to_kill(pid);
inhibiter.reset(NULL); // Unblock signals.
return std::auto_ptr< process::child >(
new process::child(new impl(pid, new process::ifdstream(fds[0]))));
}
}
/// Helper function for fork().
///
/// Please note: if you update this function to change the return type or to
/// raise different errors, do not forget to update fork() accordingly.
///
/// \param stdout_file The name of the file in which to store the stdout.
/// If this has the magic value /dev/stdout, then the parent's stdout is
/// reused without applying any redirection.
/// \param stderr_file The name of the file in which to store the stderr.
/// If this has the magic value /dev/stderr, then the parent's stderr is
/// reused without applying any redirection.
///
/// \return In the case of the parent, a new child object returned as a
/// dynamically-allocated object because children classes are unique and thus
/// noncopyable. In the case of the child, a NULL pointer.
///
/// \throw process::system_error If the call to fork(2) fails.
std::auto_ptr< process::child >
process::child::fork_files_aux(const fs::path& stdout_file,
const fs::path& stderr_file)
{
std::cout.flush();
std::cerr.flush();
std::auto_ptr< signals::interrupts_inhibiter > inhibiter(
new signals::interrupts_inhibiter);
pid_t pid = detail::syscall_fork();
if (pid == -1) {
inhibiter.reset(NULL); // Unblock signals.
throw process::system_error("fork(2) failed", errno);
} else if (pid == 0) {
inhibiter.reset(NULL); // Unblock signals.
::setpgid(::getpid(), ::getpid());
try {
if (stdout_file != fs::path("/dev/stdout")) {
const int stdout_fd = open_for_append(stdout_file);
safe_dup(stdout_fd, STDOUT_FILENO);
::close(stdout_fd);
}
if (stderr_file != fs::path("/dev/stderr")) {
const int stderr_fd = open_for_append(stderr_file);
safe_dup(stderr_fd, STDERR_FILENO);
::close(stderr_fd);
}
} catch (const system_error& e) {
std::cerr << F("Failed to set up subprocess: %s\n") % e.what();
std::abort();
}
return std::auto_ptr< process::child >(NULL);
} else {
LD(F("Spawned process %s: stdout=%s, stderr=%s") % pid % stdout_file %
stderr_file);
signals::add_pid_to_kill(pid);
inhibiter.reset(NULL); // Unblock signals.
return std::auto_ptr< process::child >(
new process::child(new impl(pid, NULL)));
}
}
/// Spawns a new binary and multiplexes and captures its stdout and stderr.
///
/// If the subprocess cannot be completely set up for any reason, it attempts to
/// dump an error message to its stderr channel and it then calls std::abort().
///
/// \param program The binary to execute.
/// \param args The arguments to pass to the binary, without the program name.
///
/// \return A new child object, returned as a dynamically-allocated object
/// because children classes are unique and thus noncopyable.
///
/// \throw process::system_error If the process cannot be spawned due to a
/// system call error.
std::auto_ptr< process::child >
process::child::spawn_capture(const fs::path& program, const args_vector& args)
{
std::auto_ptr< child > child = fork_capture_aux();
if (child.get() == NULL)
cxx_exec(program, args);
log_exec(program, args);
return child;
}
/// Spawns a new binary and redirects its stdout and stderr to files.
///
/// If the subprocess cannot be completely set up for any reason, it attempts to
/// dump an error message to its stderr channel and it then calls std::abort().
///
/// \param program The binary to execute.
/// \param args The arguments to pass to the binary, without the program name.
/// \param stdout_file The name of the file in which to store the stdout.
/// \param stderr_file The name of the file in which to store the stderr.
///
/// \return A new child object, returned as a dynamically-allocated object
/// because children classes are unique and thus noncopyable.
///
/// \throw process::system_error If the process cannot be spawned due to a
/// system call error.
std::auto_ptr< process::child >
process::child::spawn_files(const fs::path& program,
const args_vector& args,
const fs::path& stdout_file,
const fs::path& stderr_file)
{
std::auto_ptr< child > child = fork_files_aux(stdout_file, stderr_file);
if (child.get() == NULL)
cxx_exec(program, args);
log_exec(program, args);
return child;
}
/// Returns the process identifier of this child.
///
/// \return A process identifier.
int
process::child::pid(void) const
{
return _pimpl->_pid;
}
/// Gets the input stream corresponding to the stdout and stderr of the child.
///
/// \pre The child must have been started by fork_capture().
///
/// \return A reference to the input stream connected to the output of the test
/// case.
std::istream&
process::child::output(void)
{
PRE(_pimpl->_output.get() != NULL);
return *_pimpl->_output;
}
/// Blocks to wait for completion.
///
/// \return The termination status of the child process.
///
/// \throw process::system_error If the call to waitpid(2) fails.
process::status
process::child::wait(void)
{
const process::status status = safe_wait(_pimpl->_pid);
{
signals::interrupts_inhibiter inhibiter;
signals::remove_pid_to_kill(_pimpl->_pid);
}
return status;
}