In the follow-up of commit fb3041d61f68 ("kbuild: fix SIGPIPE error
message for AR=gcc-ar and AR=llvm-ar"), Kees Cook pointed out that
tools should _not_ catch their own SIGPIPEs [1] [2].
Based on his feedback, LLVM was fixed [3].
However, Python's default behavior is to show noisy bracktrace when
SIGPIPE is sent. So, scripts written in Python are basically in the
same situation as the buggy llvm tools.
Example:
$ make -s allnoconfig
$ make -s allmodconfig
$ scripts/diffconfig .config.old .config | head -n1
-ALIX n
Traceback (most recent call last):
File "/home/masahiro/linux/scripts/diffconfig", line 132, in <module>
main()
File "/home/masahiro/linux/scripts/diffconfig", line 130, in main
print_config("+", config, None, b[config])
File "/home/masahiro/linux/scripts/diffconfig", line 64, in print_config
print("+%s %s" % (config, new_value))
BrokenPipeError: [Errno 32] Broken pipe
Python documentatin [4] notes how to make scripts die immediately and
silently:
"""
Piping output of your program to tools like head(1) will cause a
SIGPIPE signal to be sent to your process when the receiver of its
standard output closes early. This results in an exception like
BrokenPipeError: [Errno 32] Broken pipe. To handle this case,
wrap your entry point to catch this exception as follows:
import os
import sys
def main():
try:
# simulate large output (your code replaces this loop)
for x in range(10000):
print("y")
# flush output here to force SIGPIPE to be triggered
# while inside this try block.
sys.stdout.flush()
except BrokenPipeError:
# Python flushes standard streams on exit; redirect remaining output
# to devnull to avoid another BrokenPipeError at shutdown
devnull = os.open(os.devnull, os.O_WRONLY)
os.dup2(devnull, sys.stdout.fileno())
sys.exit(1) # Python exits with error code 1 on EPIPE
if __name__ == '__main__':
main()
Do not set SIGPIPE’s disposition to SIG_DFL in order to avoid
BrokenPipeError. Doing that would cause your program to exit
unexpectedly whenever any socket connection is interrupted while
your program is still writing to it.
"""
Currently, tools/perf/scripts/python/intel-pt-events.py seems the
only script that fixes the issue that way.
tools/perf/scripts/python/compaction-times.py uses another approach
signal.signal(signal.SIGPIPE, signal.SIG_DFL) but the Python
documentation clearly says "Don't do it".
I cannot fix all Python scripts since there are so many.
I fixed some in the scripts/ directory.
[1]: https://lore.kernel.org/all/202211161056.1B9611A@keescook/
[2]: https://github.com/llvm/llvm-project/issues/59037
[3]: https://github.com/llvm/llvm-project/commit/4787efa38066adb51e2c049499d25b3610c0877b
[4]: https://docs.python.org/3/library/signal.html#note-on-sigpipe
Cc: Kees Cook <[email protected]>
Signed-off-by: Masahiro Yamada <[email protected]>
---
scripts/checkkconfigsymbols.py | 13 ++++++++++++-
scripts/clang-tools/run-clang-tools.py | 21 ++++++++++++++-------
scripts/diffconfig | 16 ++++++++++++++--
3 files changed, 40 insertions(+), 10 deletions(-)
diff --git a/scripts/checkkconfigsymbols.py b/scripts/checkkconfigsymbols.py
index 217d21abc86e..36c920e71313 100755
--- a/scripts/checkkconfigsymbols.py
+++ b/scripts/checkkconfigsymbols.py
@@ -115,7 +115,7 @@ def parse_options():
return args
-def main():
+def print_undefined_symbols():
"""Main function of this module."""
args = parse_options()
@@ -467,5 +467,16 @@ def parse_kconfig_file(kfile):
return defined, references
+def main():
+ try:
+ print_undefined_symbols()
+ except BrokenPipeError:
+ # Python flushes standard streams on exit; redirect remaining output
+ # to devnull to avoid another BrokenPipeError at shutdown
+ devnull = os.open(os.devnull, os.O_WRONLY)
+ os.dup2(devnull, sys.stdout.fileno())
+ sys.exit(1) # Python exits with error code 1 on EPIPE
+
+
if __name__ == "__main__":
main()
diff --git a/scripts/clang-tools/run-clang-tools.py b/scripts/clang-tools/run-clang-tools.py
index 56f2ec8f0f40..3266708a8658 100755
--- a/scripts/clang-tools/run-clang-tools.py
+++ b/scripts/clang-tools/run-clang-tools.py
@@ -61,14 +61,21 @@ def run_analysis(entry):
def main():
- args = parse_arguments()
+ try:
+ args = parse_arguments()
- lock = multiprocessing.Lock()
- pool = multiprocessing.Pool(initializer=init, initargs=(lock, args))
- # Read JSON data into the datastore variable
- with open(args.path, "r") as f:
- datastore = json.load(f)
- pool.map(run_analysis, datastore)
+ lock = multiprocessing.Lock()
+ pool = multiprocessing.Pool(initializer=init, initargs=(lock, args))
+ # Read JSON data into the datastore variable
+ with open(args.path, "r") as f:
+ datastore = json.load(f)
+ pool.map(run_analysis, datastore)
+ except BrokenPipeError:
+ # Python flushes standard streams on exit; redirect remaining output
+ # to devnull to avoid another BrokenPipeError at shutdown
+ devnull = os.open(os.devnull, os.O_WRONLY)
+ os.dup2(devnull, sys.stdout.fileno())
+ sys.exit(1) # Python exits with error code 1 on EPIPE
if __name__ == "__main__":
diff --git a/scripts/diffconfig b/scripts/diffconfig
index d5da5fa05d1d..43f0f3d273ae 100755
--- a/scripts/diffconfig
+++ b/scripts/diffconfig
@@ -65,7 +65,7 @@ def print_config(op, config, value, new_value):
else:
print(" %s %s -> %s" % (config, value, new_value))
-def main():
+def show_diff():
global merge_style
# parse command line args
@@ -129,4 +129,16 @@ def main():
for config in new:
print_config("+", config, None, b[config])
-main()
+def main():
+ try:
+ show_diff()
+ except BrokenPipeError:
+ # Python flushes standard streams on exit; redirect remaining output
+ # to devnull to avoid another BrokenPipeError at shutdown
+ devnull = os.open(os.devnull, os.O_WRONLY)
+ os.dup2(devnull, sys.stdout.fileno())
+ sys.exit(1) # Python exits with error code 1 on EPIPE
+
+
+if __name__ == '__main__':
+ main()
--
2.34.1
On Wed, Jan 11, 2023 at 6:30 PM Masahiro Yamada <[email protected]> wrote:
>
> In the follow-up of commit fb3041d61f68 ("kbuild: fix SIGPIPE error
> message for AR=gcc-ar and AR=llvm-ar"), Kees Cook pointed out that
> tools should _not_ catch their own SIGPIPEs [1] [2].
>
> Based on his feedback, LLVM was fixed [3].
>
> However, Python's default behavior is to show noisy bracktrace when
> SIGPIPE is sent. So, scripts written in Python are basically in the
> same situation as the buggy llvm tools.
>
> Example:
>
> $ make -s allnoconfig
> $ make -s allmodconfig
> $ scripts/diffconfig .config.old .config | head -n1
> -ALIX n
> Traceback (most recent call last):
> File "/home/masahiro/linux/scripts/diffconfig", line 132, in <module>
> main()
> File "/home/masahiro/linux/scripts/diffconfig", line 130, in main
> print_config("+", config, None, b[config])
> File "/home/masahiro/linux/scripts/diffconfig", line 64, in print_config
> print("+%s %s" % (config, new_value))
> BrokenPipeError: [Errno 32] Broken pipe
>
> Python documentatin [4] notes how to make scripts die immediately and
typo: s/documentatin/documentation/
> silently:
>
> """
> Piping output of your program to tools like head(1) will cause a
> SIGPIPE signal to be sent to your process when the receiver of its
> standard output closes early. This results in an exception like
> BrokenPipeError: [Errno 32] Broken pipe. To handle this case,
> wrap your entry point to catch this exception as follows:
>
> import os
> import sys
>
> def main():
> try:
> # simulate large output (your code replaces this loop)
> for x in range(10000):
> print("y")
> # flush output here to force SIGPIPE to be triggered
> # while inside this try block.
> sys.stdout.flush()
> except BrokenPipeError:
> # Python flushes standard streams on exit; redirect remaining output
> # to devnull to avoid another BrokenPipeError at shutdown
> devnull = os.open(os.devnull, os.O_WRONLY)
> os.dup2(devnull, sys.stdout.fileno())
> sys.exit(1) # Python exits with error code 1 on EPIPE
>
> if __name__ == '__main__':
> main()
>
> Do not set SIGPIPE’s disposition to SIG_DFL in order to avoid
> BrokenPipeError. Doing that would cause your program to exit
> unexpectedly whenever any socket connection is interrupted while
> your program is still writing to it.
> """
>
> Currently, tools/perf/scripts/python/intel-pt-events.py seems the
> only script that fixes the issue that way.
>
> tools/perf/scripts/python/compaction-times.py uses another approach
> signal.signal(signal.SIGPIPE, signal.SIG_DFL) but the Python
> documentation clearly says "Don't do it".
>
> I cannot fix all Python scripts since there are so many.
> I fixed some in the scripts/ directory.
That's ok; "Rome wasn't built in a day." This is a good start!
Thank you for the patch!
Reviewed-by: Nick Desaulniers <[email protected]>
>
> [1]: https://lore.kernel.org/all/202211161056.1B9611A@keescook/
> [2]: https://github.com/llvm/llvm-project/issues/59037
> [3]: https://github.com/llvm/llvm-project/commit/4787efa38066adb51e2c049499d25b3610c0877b
> [4]: https://docs.python.org/3/library/signal.html#note-on-sigpipe
>
> Cc: Kees Cook <[email protected]>
> Signed-off-by: Masahiro Yamada <[email protected]>
> ---
>
> scripts/checkkconfigsymbols.py | 13 ++++++++++++-
> scripts/clang-tools/run-clang-tools.py | 21 ++++++++++++++-------
> scripts/diffconfig | 16 ++++++++++++++--
> 3 files changed, 40 insertions(+), 10 deletions(-)
>
> diff --git a/scripts/checkkconfigsymbols.py b/scripts/checkkconfigsymbols.py
> index 217d21abc86e..36c920e71313 100755
> --- a/scripts/checkkconfigsymbols.py
> +++ b/scripts/checkkconfigsymbols.py
> @@ -115,7 +115,7 @@ def parse_options():
> return args
>
>
> -def main():
> +def print_undefined_symbols():
> """Main function of this module."""
> args = parse_options()
>
> @@ -467,5 +467,16 @@ def parse_kconfig_file(kfile):
> return defined, references
>
>
> +def main():
> + try:
> + print_undefined_symbols()
> + except BrokenPipeError:
> + # Python flushes standard streams on exit; redirect remaining output
> + # to devnull to avoid another BrokenPipeError at shutdown
> + devnull = os.open(os.devnull, os.O_WRONLY)
> + os.dup2(devnull, sys.stdout.fileno())
> + sys.exit(1) # Python exits with error code 1 on EPIPE
> +
> +
> if __name__ == "__main__":
> main()
> diff --git a/scripts/clang-tools/run-clang-tools.py b/scripts/clang-tools/run-clang-tools.py
> index 56f2ec8f0f40..3266708a8658 100755
> --- a/scripts/clang-tools/run-clang-tools.py
> +++ b/scripts/clang-tools/run-clang-tools.py
> @@ -61,14 +61,21 @@ def run_analysis(entry):
>
>
> def main():
> - args = parse_arguments()
> + try:
> + args = parse_arguments()
>
> - lock = multiprocessing.Lock()
> - pool = multiprocessing.Pool(initializer=init, initargs=(lock, args))
> - # Read JSON data into the datastore variable
> - with open(args.path, "r") as f:
> - datastore = json.load(f)
> - pool.map(run_analysis, datastore)
> + lock = multiprocessing.Lock()
> + pool = multiprocessing.Pool(initializer=init, initargs=(lock, args))
> + # Read JSON data into the datastore variable
> + with open(args.path, "r") as f:
> + datastore = json.load(f)
> + pool.map(run_analysis, datastore)
> + except BrokenPipeError:
> + # Python flushes standard streams on exit; redirect remaining output
> + # to devnull to avoid another BrokenPipeError at shutdown
> + devnull = os.open(os.devnull, os.O_WRONLY)
> + os.dup2(devnull, sys.stdout.fileno())
> + sys.exit(1) # Python exits with error code 1 on EPIPE
>
>
> if __name__ == "__main__":
> diff --git a/scripts/diffconfig b/scripts/diffconfig
> index d5da5fa05d1d..43f0f3d273ae 100755
> --- a/scripts/diffconfig
> +++ b/scripts/diffconfig
> @@ -65,7 +65,7 @@ def print_config(op, config, value, new_value):
> else:
> print(" %s %s -> %s" % (config, value, new_value))
>
> -def main():
> +def show_diff():
> global merge_style
>
> # parse command line args
> @@ -129,4 +129,16 @@ def main():
> for config in new:
> print_config("+", config, None, b[config])
>
> -main()
> +def main():
> + try:
> + show_diff()
> + except BrokenPipeError:
> + # Python flushes standard streams on exit; redirect remaining output
> + # to devnull to avoid another BrokenPipeError at shutdown
> + devnull = os.open(os.devnull, os.O_WRONLY)
> + os.dup2(devnull, sys.stdout.fileno())
> + sys.exit(1) # Python exits with error code 1 on EPIPE
> +
> +
> +if __name__ == '__main__':
> + main()
> --
> 2.34.1
>
--
Thanks,
~Nick Desaulniers
On Thu, Jan 12, 2023 at 10:55:45AM -0800 Nick Desaulniers wrote:
> On Wed, Jan 11, 2023 at 6:30 PM Masahiro Yamada <[email protected]> wrote:
> >
> > In the follow-up of commit fb3041d61f68 ("kbuild: fix SIGPIPE error
> > message for AR=gcc-ar and AR=llvm-ar"), Kees Cook pointed out that
> > tools should _not_ catch their own SIGPIPEs [1] [2].
> >
> > Based on his feedback, LLVM was fixed [3].
> >
> > However, Python's default behavior is to show noisy bracktrace when
> > SIGPIPE is sent. So, scripts written in Python are basically in the
> > same situation as the buggy llvm tools.
> >
> > Example:
> >
> > $ make -s allnoconfig
> > $ make -s allmodconfig
> > $ scripts/diffconfig .config.old .config | head -n1
> > -ALIX n
> > Traceback (most recent call last):
> > File "/home/masahiro/linux/scripts/diffconfig", line 132, in <module>
> > main()
> > File "/home/masahiro/linux/scripts/diffconfig", line 130, in main
> > print_config("+", config, None, b[config])
> > File "/home/masahiro/linux/scripts/diffconfig", line 64, in print_config
> > print("+%s %s" % (config, new_value))
> > BrokenPipeError: [Errno 32] Broken pipe
> >
> > Python documentatin [4] notes how to make scripts die immediately and
>
> typo: s/documentatin/documentation/
>
> > silently:
> >
> > """
> > Piping output of your program to tools like head(1) will cause a
> > SIGPIPE signal to be sent to your process when the receiver of its
> > standard output closes early. This results in an exception like
> > BrokenPipeError: [Errno 32] Broken pipe. To handle this case,
> > wrap your entry point to catch this exception as follows:
> >
> > import os
> > import sys
> >
> > def main():
> > try:
> > # simulate large output (your code replaces this loop)
> > for x in range(10000):
> > print("y")
> > # flush output here to force SIGPIPE to be triggered
> > # while inside this try block.
> > sys.stdout.flush()
> > except BrokenPipeError:
> > # Python flushes standard streams on exit; redirect remaining output
> > # to devnull to avoid another BrokenPipeError at shutdown
> > devnull = os.open(os.devnull, os.O_WRONLY)
> > os.dup2(devnull, sys.stdout.fileno())
> > sys.exit(1) # Python exits with error code 1 on EPIPE
> >
> > if __name__ == '__main__':
> > main()
> >
> > Do not set SIGPIPE’s disposition to SIG_DFL in order to avoid
> > BrokenPipeError. Doing that would cause your program to exit
> > unexpectedly whenever any socket connection is interrupted while
> > your program is still writing to it.
> > """
> >
> > Currently, tools/perf/scripts/python/intel-pt-events.py seems the
Hi Masahiro,
should it be "... seems to be the ..."?
Reviewed-by: Nicolas Schier <[email protected]>
> > only script that fixes the issue that way.
> >
> > tools/perf/scripts/python/compaction-times.py uses another approach
> > signal.signal(signal.SIGPIPE, signal.SIG_DFL) but the Python
> > documentation clearly says "Don't do it".
> >
> > I cannot fix all Python scripts since there are so many.
> > I fixed some in the scripts/ directory.
>
> That's ok; "Rome wasn't built in a day." This is a good start!
> Thank you for the patch!
> Reviewed-by: Nick Desaulniers <[email protected]>
>
> >
> > [1]: https://lore.kernel.org/all/202211161056.1B9611A@keescook/
> > [2]: https://github.com/llvm/llvm-project/issues/59037
> > [3]: https://github.com/llvm/llvm-project/commit/4787efa38066adb51e2c049499d25b3610c0877b
> > [4]: https://docs.python.org/3/library/signal.html#note-on-sigpipe
> >
> > Cc: Kees Cook <[email protected]>
> > Signed-off-by: Masahiro Yamada <[email protected]>
> > ---
> >
> > scripts/checkkconfigsymbols.py | 13 ++++++++++++-
> > scripts/clang-tools/run-clang-tools.py | 21 ++++++++++++++-------
> > scripts/diffconfig | 16 ++++++++++++++--
> > 3 files changed, 40 insertions(+), 10 deletions(-)
> >
> > diff --git a/scripts/checkkconfigsymbols.py b/scripts/checkkconfigsymbols.py
> > index 217d21abc86e..36c920e71313 100755
> > --- a/scripts/checkkconfigsymbols.py
> > +++ b/scripts/checkkconfigsymbols.py
> > @@ -115,7 +115,7 @@ def parse_options():
> > return args
> >
> >
> > -def main():
> > +def print_undefined_symbols():
> > """Main function of this module."""
> > args = parse_options()
> >
> > @@ -467,5 +467,16 @@ def parse_kconfig_file(kfile):
> > return defined, references
> >
> >
> > +def main():
> > + try:
> > + print_undefined_symbols()
> > + except BrokenPipeError:
> > + # Python flushes standard streams on exit; redirect remaining output
> > + # to devnull to avoid another BrokenPipeError at shutdown
> > + devnull = os.open(os.devnull, os.O_WRONLY)
> > + os.dup2(devnull, sys.stdout.fileno())
> > + sys.exit(1) # Python exits with error code 1 on EPIPE
> > +
> > +
> > if __name__ == "__main__":
> > main()
> > diff --git a/scripts/clang-tools/run-clang-tools.py b/scripts/clang-tools/run-clang-tools.py
> > index 56f2ec8f0f40..3266708a8658 100755
> > --- a/scripts/clang-tools/run-clang-tools.py
> > +++ b/scripts/clang-tools/run-clang-tools.py
> > @@ -61,14 +61,21 @@ def run_analysis(entry):
> >
> >
> > def main():
> > - args = parse_arguments()
> > + try:
> > + args = parse_arguments()
> >
> > - lock = multiprocessing.Lock()
> > - pool = multiprocessing.Pool(initializer=init, initargs=(lock, args))
> > - # Read JSON data into the datastore variable
> > - with open(args.path, "r") as f:
> > - datastore = json.load(f)
> > - pool.map(run_analysis, datastore)
> > + lock = multiprocessing.Lock()
> > + pool = multiprocessing.Pool(initializer=init, initargs=(lock, args))
> > + # Read JSON data into the datastore variable
> > + with open(args.path, "r") as f:
> > + datastore = json.load(f)
> > + pool.map(run_analysis, datastore)
> > + except BrokenPipeError:
> > + # Python flushes standard streams on exit; redirect remaining output
> > + # to devnull to avoid another BrokenPipeError at shutdown
> > + devnull = os.open(os.devnull, os.O_WRONLY)
> > + os.dup2(devnull, sys.stdout.fileno())
> > + sys.exit(1) # Python exits with error code 1 on EPIPE
> >
> >
> > if __name__ == "__main__":
> > diff --git a/scripts/diffconfig b/scripts/diffconfig
> > index d5da5fa05d1d..43f0f3d273ae 100755
> > --- a/scripts/diffconfig
> > +++ b/scripts/diffconfig
> > @@ -65,7 +65,7 @@ def print_config(op, config, value, new_value):
> > else:
> > print(" %s %s -> %s" % (config, value, new_value))
> >
> > -def main():
> > +def show_diff():
> > global merge_style
> >
> > # parse command line args
> > @@ -129,4 +129,16 @@ def main():
> > for config in new:
> > print_config("+", config, None, b[config])
> >
> > -main()
> > +def main():
> > + try:
> > + show_diff()
> > + except BrokenPipeError:
> > + # Python flushes standard streams on exit; redirect remaining output
> > + # to devnull to avoid another BrokenPipeError at shutdown
> > + devnull = os.open(os.devnull, os.O_WRONLY)
> > + os.dup2(devnull, sys.stdout.fileno())
> > + sys.exit(1) # Python exits with error code 1 on EPIPE
> > +
> > +
> > +if __name__ == '__main__':
> > + main()
> > --
> > 2.34.1
> >
>
>
> --
> Thanks,
> ~Nick Desaulniers
On Thu, Jan 12, 2023 at 11:30:06AM +0900, Masahiro Yamada wrote:
> def main():
> try:
> # simulate large output (your code replaces this loop)
> for x in range(10000):
> print("y")
> # flush output here to force SIGPIPE to be triggered
> # while inside this try block.
> sys.stdout.flush()
> except BrokenPipeError:
> # Python flushes standard streams on exit; redirect remaining output
> # to devnull to avoid another BrokenPipeError at shutdown
> devnull = os.open(os.devnull, os.O_WRONLY)
> os.dup2(devnull, sys.stdout.fileno())
> sys.exit(1) # Python exits with error code 1 on EPIPE
I still think this is wrong -- they should not continue piping, and
should just die with SIGPIPE. It should simply be:
signal(SIGPIPE, SIG_DFL);
Nothing else needed. No wasted CPU cycles, shell handling continues as
per normal.
> if __name__ == '__main__':
> main()
>
> Do not set SIGPIPE’s disposition to SIG_DFL in order to avoid
> BrokenPipeError. Doing that would cause your program to exit
> unexpectedly whenever any socket connection is interrupted while
> your program is still writing to it.
This advise is for socket programs, not command-line tools.
-Kees
--
Kees Cook
On Fri, Jan 13, 2023 at 7:06 AM Kees Cook <[email protected]> wrote:
>
> On Thu, Jan 12, 2023 at 11:30:06AM +0900, Masahiro Yamada wrote:
> > def main():
> > try:
> > # simulate large output (your code replaces this loop)
> > for x in range(10000):
> > print("y")
> > # flush output here to force SIGPIPE to be triggered
> > # while inside this try block.
> > sys.stdout.flush()
> > except BrokenPipeError:
> > # Python flushes standard streams on exit; redirect remaining output
> > # to devnull to avoid another BrokenPipeError at shutdown
> > devnull = os.open(os.devnull, os.O_WRONLY)
> > os.dup2(devnull, sys.stdout.fileno())
> > sys.exit(1) # Python exits with error code 1 on EPIPE
>
> I still think this is wrong -- they should not continue piping, and
> should just die with SIGPIPE. It should simply be:
>
> signal(SIGPIPE, SIG_DFL);
>
> Nothing else needed. No wasted CPU cycles, shell handling continues as
> per normal.
I prefer try-and-except because it is Python's coding style,
and we can do something before the exit.
(for example, clean up temporary files)
>
> > if __name__ == '__main__':
> > main()
> >
> > Do not set SIGPIPE’s disposition to SIG_DFL in order to avoid
> > BrokenPipeError. Doing that would cause your program to exit
> > unexpectedly whenever any socket connection is interrupted while
> > your program is still writing to it.
>
> This advise is for socket programs, not command-line tools.
I still do not understand what is bad
about using this for command-line tools.
>
> -Kees
>
> --
> Kees Cook
--
Best Regards
Masahiro Yamada
On Sun, Jan 15, 2023 at 12:04 PM Masahiro Yamada <[email protected]> wrote:
>
> On Fri, Jan 13, 2023 at 7:06 AM Kees Cook <[email protected]> wrote:
> >
> > On Thu, Jan 12, 2023 at 11:30:06AM +0900, Masahiro Yamada wrote:
> > > def main():
> > > try:
> > > # simulate large output (your code replaces this loop)
> > > for x in range(10000):
> > > print("y")
> > > # flush output here to force SIGPIPE to be triggered
> > > # while inside this try block.
> > > sys.stdout.flush()
> > > except BrokenPipeError:
> > > # Python flushes standard streams on exit; redirect remaining output
> > > # to devnull to avoid another BrokenPipeError at shutdown
> > > devnull = os.open(os.devnull, os.O_WRONLY)
> > > os.dup2(devnull, sys.stdout.fileno())
> > > sys.exit(1) # Python exits with error code 1 on EPIPE
> >
> > I still think this is wrong -- they should not continue piping, and
> > should just die with SIGPIPE. It should simply be:
> >
> > signal(SIGPIPE, SIG_DFL);
> >
> > Nothing else needed. No wasted CPU cycles, shell handling continues as
> > per normal.
>
>
> I prefer try-and-except because it is Python's coding style,
> and we can do something before the exit.
> (for example, clean up temporary files)
>
>
> >
> > > if __name__ == '__main__':
> > > main()
> > >
> > > Do not set SIGPIPE’s disposition to SIG_DFL in order to avoid
> > > BrokenPipeError. Doing that would cause your program to exit
> > > unexpectedly whenever any socket connection is interrupted while
> > > your program is still writing to it.
> >
> > This advise is for socket programs, not command-line tools.
>
>
> I still do not understand what is bad
> about using this for command-line tools.
>
>
> >
> > -Kees
> >
> > --
> > Kees Cook
>
>
>
> --
> Best Regards
> Masahiro Yamada
Applied with the typos fixes.
--
Best Regards
Masahiro Yamada