Issue 20947: -Wstrict-overflow findings - Python tracker (original) (raw)

Issue20947

Created on 2014-03-16 17:39 by Jeffrey.Walton, last changed 2022-04-11 14:58 by admin. This issue is now closed.

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Messages (7)
msg213742 - (view)	Author: Jeffrey Walton (Jeffrey.Walton) *	Date: 2014-03-16 17:39
$ hg id 3736bf94535c+ tip Forgive me if you were aware of these. /usr/bin/gcc -pthread -fPIC -Wno-unused-result -Werror=declaration-after-statement -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -fno-common -Wstrict-overflow -Wformat=2 -Wformat-security -Wcast-align -Wtrampolines -fno-common -Wstrict-overflow -Wformat=2 -Wformat-security -Wcast-align -Wtrampolines -I./Include -I. -IInclude -I/usr/include/x86_64-linux-gnu -I/usr/local/include -Icpython/./Include -Icpython/. -c cpython/./Modules/_posixsubprocess.c -o build/temp.linux-x86_64-3.4cpython/./Modules/_posixsubprocess.o cpython/./Modules/_posixsubprocess.c: In function ‘child_exec’: cpython/./Modules/_posixsubprocess.c:491:33: warning: assuming pointer wraparound does not occur when comparing P +- C1 with P +- C2 [-Wstrict-overflow] cpython/./Modules/_posixsubprocess.c: In function ‘subprocess_fork_exec’: cpython/./Modules/_posixsubprocess.c:491:33: warning: assuming pointer wraparound does not occur when comparing P +- C1 with P +- C2 [-Wstrict-overflow] cpython/./Modules/_posixsubprocess.c:491:33: warning: assuming pointer wraparound does not occur when comparing P +- C1 with P +- C2 [-Wstrict-overflow] cpython/./Modules/_posixsubprocess.c:491:33: warning: assuming pointer wraparound does not occur when comparing P +- C1 with P +- C2 [-Wstrict-overflow] ... /usr/bin/gcc -pthread -fPIC -Wno-unused-result -Werror=declaration-after-statement -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -fno-common -Wstrict-overflow -Wformat=2 -Wformat-security -Wcast-align -Wtrampolines -fno-common -Wstrict-overflow -Wformat=2 -Wformat-security -Wcast-align -Wtrampolines -I./Include -I. -IInclude -I/usr/include/x86_64-linux-gnu -I/usr/local/include -Icpython/./Include -Icpython/. -c cpython/./Modules/sha512module.c -o build/temp.linux-x86_64-3.4cpython/./Modules/sha512module.o cpython/./Modules/sha512module.c: In function ‘sha512_transform’: cpython/./Modules/sha512module.c:128:1: warning: assuming pointer wraparound does not occur when comparing P +- C1 with P +- C2 [-Wstrict-overflow] cpython/./Modules/sha512module.c:128:1: warning: assuming pointer wraparound does not occur when comparing P +- C1 with P +- C2 [-Wstrict-overflow]
msg235817 - (view)	Author: Mark Lawrence (BreamoreBoy) *	Date: 2015-02-12 12:18
@Serhiy/Victor I believe that you're both interested in this type of problem.
msg271508 - (view)	Author: Martin Panter (martin.panter) *	Date: 2016-07-28 08:07
Regarding the warning in Modules/_posixsubprocess.c, I don’t see any problem. I’m not sure exactly what it is warning about. Maybe if the cur pointer ever gets _before_ the start of hex_errno, that could be a problem, but the loop should stop when it reaches the start. The warnings in Modules/sha512module.c refer to the first line of the sha512_transform() function. I cannot see any pointer comparisons in that function. The closest is pointer and array indexing, but it all seems to be in order. I propose to ignore these warnings.
msg277375 - (view)	Author: Christian Heimes (christian.heimes) *	Date: 2016-09-25 13:18
I can no longer reproduce the warnings with $ CFLAGS=-Wstrict-overflow ./configure -C --with-pydebug --silent $ make --silent
msg277378 - (view)	Author: Serhiy Storchaka (serhiy.storchaka) *	Date: 2016-09-25 14:34
I can reproduce warnings in Modules/_posixsubprocess.c: gcc -pthread -fPIC -Wno-unused-result -Wsign-compare -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -std=c99 -Wextra -Wno-unused-result -Wno-unused-parameter -Wno-missing-field-initializers -Wstrict-overflow -I./Include -I. -I/usr/include/i386-linux-gnu -I/usr/local/include -I/home/serhiy/py/cpython/Include -I/home/serhiy/py/cpython -c /home/serhiy/py/cpython/Modules/_posixsubprocess.c -o build/temp.linux-i686-3.7/home/serhiy/py/cpython/Modules/_posixsubprocess.o /home/serhiy/py/cpython/Modules/_posixsubprocess.c: In function ‘child_exec’: /home/serhiy/py/cpython/Modules/_posixsubprocess.c:524:33: warning: assuming pointer wraparound does not occur when comparing P +- C1 with P +- C2 [-Wstrict-overflow] while (saved_errno != 0 && cur > hex_errno) { ^ /home/serhiy/py/cpython/Modules/_posixsubprocess.c: In function ‘subprocess_fork_exec’: /home/serhiy/py/cpython/Modules/_posixsubprocess.c:524:33: warning: assuming pointer wraparound does not occur when comparing P +- C1 with P +- C2 [-Wstrict-overflow] while (saved_errno != 0 && cur > hex_errno) { ^ /home/serhiy/py/cpython/Modules/_posixsubprocess.c:544:1: warning: assuming pointer wraparound does not occur when comparing P +- C1 with P +- C2 [-Wstrict-overflow] subprocess_fork_exec(PyObject* self, PyObject *args) ^ /home/serhiy/py/cpython/Modules/_posixsubprocess.c:544:1: warning: assuming pointer wraparound does not occur when comparing P +- C1 with P +- C2 [-Wstrict-overflow] /home/serhiy/py/cpython/Modules/_posixsubprocess.c:524:33: warning: assuming pointer wraparound does not occur when comparing P +- C1 with P +- C2 [-Wstrict-overflow] while (saved_errno != 0 && cur > hex_errno) { ^ /home/serhiy/py/cpython/Modules/_posixsubprocess.c:524:33: warning: assuming pointer wraparound does not occur when comparing P +- C1 with P +- C2 [-Wstrict-overflow] Proposed simple patch fixes this.
msg277379 - (view)	Author: Serhiy Storchaka (serhiy.storchaka) *	Date: 2016-09-25 14:35
Use following command for reproducing: make -s CFLAGS=-Wstrict-overflow
msg277540 - (view)	Author: Roundup Robot (python-dev)	Date: 2016-09-27 19:05
New changeset dad879edefd2 by Serhiy Storchaka in branch '3.5': Issue #20947: Fixed a gcc warning with -Wstrict-overflow. https://hg.python.org/cpython/rev/dad879edefd2 New changeset 5ecbe8a55ccd by Serhiy Storchaka in branch '3.6': Issue #20947: Fixed a gcc warning with -Wstrict-overflow. https://hg.python.org/cpython/rev/5ecbe8a55ccd New changeset 675d3f76444d by Serhiy Storchaka in branch 'default': Issue #20947: Fixed a gcc warning with -Wstrict-overflow. https://hg.python.org/cpython/rev/675d3f76444d