Re: [PATCH v3] libiberty: Use posix_spawn in pex-unix when available.

[Prathamesh Kulkarni <prathamesh.kulkarni@linaro.org>]

On Thu, 5 Oct 2023 at 00:00, Brendan Shanks <bshanks@codeweavers.com> wrote:
>
> Hi,
>
> This patch implements pex_unix_exec_child using posix_spawn when
> available.
>
> This should especially benefit recent macOS (where vfork just calls
> fork), but should have equivalent or faster performance on all
> platforms.
> In addition, the implementation is substantially simpler than the
> vfork+exec code path.
>
> Tested on x86_64-linux.
Hi Brendan,
It seems this patch caused the following regressions on aarch64:

FAIL: g++.dg/modules/bad-mapper-1.C -std=c++17  at line 3 (test for
errors, line )
FAIL: g++.dg/modules/bad-mapper-1.C -std=c++17 (test for excess errors)
FAIL: g++.dg/modules/bad-mapper-1.C -std=c++2a  at line 3 (test for
errors, line )
FAIL: g++.dg/modules/bad-mapper-1.C -std=c++2a (test for excess errors)
FAIL: g++.dg/modules/bad-mapper-1.C -std=c++2b  at line 3 (test for
errors, line )
FAIL: g++.dg/modules/bad-mapper-1.C -std=c++2b (test for excess errors)

Looking at g++.log:
/home/tcwg-buildslave/workspace/tcwg_gnu_2/abe/snapshots/gcc.git~master/gcc/testsuite/g++.dg/modules/bad-mapper-1.C:
error: failed posix_spawnp mapper 'this-will-not-work'
In module imported at
/home/tcwg-buildslave/workspace/tcwg_gnu_2/abe/snapshots/gcc.git~master/gcc/testsuite/g++.dg/modules/bad-mapper-1.C:2:1:
unique1.bob: error: failed to read compiled module: No such file or directory
unique1.bob: note: compiled module file is 'gcm.cache/unique1.bob.gcm'
unique1.bob: note: imports must be built before being imported
unique1.bob: fatal error: returning to the gate for a mechanical issue
compilation terminated.

Link to log files:
https://ci.linaro.org/job/tcwg_gcc_check--master-aarch64-build/1159/artifact/artifacts/00-sumfiles/
Could you please investigate ?

Thanks,
Prathamesh
>
> v2: Fix error handling (previously the function would be run twice in
> case of error), and don't use a macro that changes control flow.
>
> v3: Match file style for error-handling blocks, don't close
> in/out/errdes on error, and check close() for errors.
>
> libiberty/
>         * configure.ac (AC_CHECK_HEADERS): Add spawn.h.
>         (checkfuncs): Add posix_spawn, posix_spawnp.
>         (AC_CHECK_FUNCS): Add posix_spawn, posix_spawnp.
>         * configure, config.in: Rebuild.
>         * pex-unix.c [HAVE_POSIX_SPAWN] (pex_unix_exec_child): New function.
>
> Signed-off-by: Brendan Shanks <bshanks@codeweavers.com>
> ---
>  libiberty/configure.ac |   8 +-
>  libiberty/pex-unix.c   | 168 +++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 173 insertions(+), 3 deletions(-)
>
> diff --git a/libiberty/configure.ac b/libiberty/configure.ac
> index 0748c592704..2488b031bc8 100644
> --- a/libiberty/configure.ac
> +++ b/libiberty/configure.ac
> @@ -289,7 +289,7 @@ AC_SUBST_FILE(host_makefile_frag)
>  # It's OK to check for header files.  Although the compiler may not be
>  # able to link anything, it had better be able to at least compile
>  # something.
> -AC_CHECK_HEADERS(sys/file.h sys/param.h limits.h stdlib.h malloc.h string.h unistd.h strings.h sys/time.h time.h sys/resource.h sys/stat.h sys/mman.h fcntl.h alloca.h sys/pstat.h sys/sysmp.h sys/sysinfo.h machine/hal_sysinfo.h sys/table.h sys/sysctl.h sys/systemcfg.h stdint.h stdio_ext.h process.h sys/prctl.h)
> +AC_CHECK_HEADERS(sys/file.h sys/param.h limits.h stdlib.h malloc.h string.h unistd.h strings.h sys/time.h time.h sys/resource.h sys/stat.h sys/mman.h fcntl.h alloca.h sys/pstat.h sys/sysmp.h sys/sysinfo.h machine/hal_sysinfo.h sys/table.h sys/sysctl.h sys/systemcfg.h stdint.h stdio_ext.h process.h sys/prctl.h spawn.h)
>  AC_HEADER_SYS_WAIT
>  AC_HEADER_TIME
>
> @@ -412,7 +412,8 @@ funcs="$funcs setproctitle"
>  vars="sys_errlist sys_nerr sys_siglist"
>
>  checkfuncs="__fsetlocking canonicalize_file_name dup3 getrlimit getrusage \
> - getsysinfo gettimeofday on_exit pipe2 psignal pstat_getdynamic pstat_getstatic \
> + getsysinfo gettimeofday on_exit pipe2 posix_spawn posix_spawnp psignal \
> + pstat_getdynamic pstat_getstatic \
>   realpath setrlimit spawnve spawnvpe strerror strsignal sysconf sysctl \
>   sysmp table times wait3 wait4"
>
> @@ -435,7 +436,8 @@ if test "x" = "y"; then
>      index insque \
>      memchr memcmp memcpy memmem memmove memset mkstemps \
>      on_exit \
> -    pipe2 psignal pstat_getdynamic pstat_getstatic putenv \
> +    pipe2 posix_spawn posix_spawnp psignal \
> +    pstat_getdynamic pstat_getstatic putenv \
>      random realpath rename rindex \
>      sbrk setenv setproctitle setrlimit sigsetmask snprintf spawnve spawnvpe \
>       stpcpy stpncpy strcasecmp strchr strdup \
> diff --git a/libiberty/pex-unix.c b/libiberty/pex-unix.c
> index 33b5bce31c2..336799d1125 100644
> --- a/libiberty/pex-unix.c
> +++ b/libiberty/pex-unix.c
> @@ -58,6 +58,9 @@ extern int errno;
>  #ifdef HAVE_PROCESS_H
>  #include <process.h>
>  #endif
> +#ifdef HAVE_SPAWN_H
> +#include <spawn.h>
> +#endif
>
>  #ifdef vfork /* Autoconf may define this to fork for us. */
>  # define VFORK_STRING "fork"
> @@ -559,6 +562,171 @@ pex_unix_exec_child (struct pex_obj *obj ATTRIBUTE_UNUSED,
>    return (pid_t) -1;
>  }
>
> +#elif defined(HAVE_POSIX_SPAWN) && defined(HAVE_POSIX_SPAWNP)
> +/* Implementation of pex->exec_child using posix_spawn.            */
> +
> +static pid_t
> +pex_unix_exec_child (struct pex_obj *obj ATTRIBUTE_UNUSED,
> +                    int flags, const char *executable,
> +                    char * const * argv, char * const * env,
> +                    int in, int out, int errdes,
> +                    int toclose, const char **errmsg, int *err)
> +{
> +  int ret;
> +  pid_t pid = -1;
> +  posix_spawnattr_t attr;
> +  posix_spawn_file_actions_t actions;
> +  int attr_initialized = 0, actions_initialized = 0;
> +
> +  *err = 0;
> +
> +  ret = posix_spawnattr_init (&attr);
> +  if (ret)
> +    {
> +      *err = ret;
> +      *errmsg = "posix_spawnattr_init";
> +      goto exit;
> +    }
> +  attr_initialized = 1;
> +
> +  /* Use vfork() on glibc <=2.24. */
> +#ifdef POSIX_SPAWN_USEVFORK
> +  ret = posix_spawnattr_setflags (&attr, POSIX_SPAWN_USEVFORK);
> +  if (ret)
> +    {
> +      *err = ret;
> +      *errmsg = "posix_spawnattr_setflags";
> +      goto exit;
> +    }
> +#endif
> +
> +  ret = posix_spawn_file_actions_init (&actions);
> +  if (ret)
> +    {
> +      *err = ret;
> +      *errmsg = "posix_spawn_file_actions_init";
> +      goto exit;
> +    }
> +  actions_initialized = 1;
> +
> +  if (in != STDIN_FILE_NO)
> +    {
> +      ret = posix_spawn_file_actions_adddup2 (&actions, in, STDIN_FILE_NO);
> +      if (ret)
> +        {
> +          *err = ret;
> +          *errmsg = "posix_spawn_file_actions_adddup2";
> +          goto exit;
> +        }
> +
> +      ret = posix_spawn_file_actions_addclose (&actions, in);
> +      if (ret)
> +        {
> +          *err = ret;
> +          *errmsg = "posix_spawn_file_actions_addclose";
> +          goto exit;
> +        }
> +    }
> +
> +  if (out != STDOUT_FILE_NO)
> +    {
> +      ret = posix_spawn_file_actions_adddup2 (&actions, out, STDOUT_FILE_NO);
> +      if (ret)
> +        {
> +          *err = ret;
> +          *errmsg = "posix_spawn_file_actions_adddup2";
> +          goto exit;
> +        }
> +
> +      ret = posix_spawn_file_actions_addclose (&actions, out);
> +      if (ret)
> +        {
> +          *err = ret;
> +          *errmsg = "posix_spawn_file_actions_addclose";
> +          goto exit;
> +        }
> +    }
> +
> +  if (errdes != STDERR_FILE_NO)
> +    {
> +      ret = posix_spawn_file_actions_adddup2 (&actions, errdes, STDERR_FILE_NO);
> +      if (ret)
> +        {
> +          *err = ret;
> +          *errmsg = "posix_spawn_file_actions_adddup2";
> +          goto exit;
> +        }
> +
> +      ret = posix_spawn_file_actions_addclose (&actions, errdes);
> +      if (ret)
> +        {
> +          *err = ret;
> +          *errmsg = "posix_spawn_file_actions_addclose";
> +          goto exit;
> +        }
> +    }
> +
> +  if (toclose >= 0)
> +    {
> +      ret = posix_spawn_file_actions_addclose (&actions, toclose);
> +      if (ret)
> +        {
> +          *err = ret;
> +          *errmsg = "posix_spawn_file_actions_addclose";
> +          goto exit;
> +        }
> +    }
> +
> +  if ((flags & PEX_STDERR_TO_STDOUT) != 0)
> +    {
> +      ret = posix_spawn_file_actions_adddup2 (&actions, STDOUT_FILE_NO, STDERR_FILE_NO);
> +      if (ret)
> +        {
> +          *err = ret;
> +          *errmsg = "posix_spawn_file_actions_adddup2";
> +          goto exit;
> +        }
> +    }
> +
> +  if ((flags & PEX_SEARCH) != 0)
> +    {
> +      ret = posix_spawnp (&pid, executable, &actions, &attr, argv, env ? env : environ);
> +      if (ret)
> +        {
> +          *err = ret;
> +          *errmsg = "posix_spawnp";
> +          goto exit;
> +        }
> +    }
> +  else
> +    {
> +      ret = posix_spawn (&pid, executable, &actions, &attr, argv, env ? env : environ);
> +      if (ret)
> +        {
> +          *err = ret;
> +          *errmsg = "posix_spawn";
> +          goto exit;
> +        }
> +    }
> +
> +exit:
> +  if (actions_initialized)
> +    posix_spawn_file_actions_destroy (&actions);
> +  if (attr_initialized)
> +    posix_spawnattr_destroy (&attr);
> +
> +  if (!*err && in != STDIN_FILE_NO)
> +    if (close (in))
> +      *errmsg = "close", *err = errno, pid = -1;
> +  if (!*err && out != STDOUT_FILE_NO)
> +    if (close (out))
> +      *errmsg = "close", *err = errno, pid = -1;
> +  if (!*err && errdes != STDERR_FILE_NO)
> +    if (close (errdes))
> +      *errmsg = "close", *err = errno, pid = -1;
> +
> +  return pid;
> +}
>  #else
>  /* Implementation of pex->exec_child using standard vfork + exec.  */
>
> --
> 2.41.0
>