Issue 22206: PyThread_create_key(): fix comparison between signed and unsigned numbers in Python/thread_pthread.h (original) (raw)

Issue22206

Created on 2014-08-15 21:45 by vstinner, last changed 2022-04-11 14:58 by admin. This issue is now closed.

Messages (4)
msg225367 - (view)	Author: STINNER Victor (vstinner) *	Date: 2014-08-15 21:45
The issue #22110 enabled more compiler warnings. I would like to fix this one: --- gcc -pthread -c -Wno-unused-result -Wsign-compare -g -O0 -Wall -Wstrict-prototypes -Werror=declaration-after-statement -I. -IInclude -I./Include -DPy_BUILD_CORE -o Python/thread.o Python/thread.c In file included from Python/thread.c:86:0: Python/thread_pthread.h: In function ‘PyThread_create_key’: Python/thread_pthread.h:611:22: attention : signed and unsigned type in conditional expression [-Wsign-compare] return fail ? -1 : key; ^ --- Attached patch uses Py_SAFE_DOWNCAST() to explicitly downcast to int. On Linux (on my Fedora 20/amd64), pthread_key_t is defined as an unsigned int, whereas the result type of PyThread_create_key is a signed int. Nobody complained before, so I get that nobody noticed the possible overflow for a key > INT_MAX. I checked the code, we only check if PyThread_create_key() returns -1, if you reach UINT_MAX keys. UINT_MAX keys sounds insane, you probably hit another limit before. On Linux, it looks like the key is a counter and deleted values are reused: haypo@selma$ ./python Python 3.5.0a0 (default:a0b38f4eb79e, Aug 15 2014, 23:37:42) [GCC 4.8.3 20140624 (Red Hat 4.8.3-1)] on linux Type "help", "copyright", "credits" or "license" for more information. >>> import ctypes >>> ctypes.pythonapi.PyThread_create_key() 2 >>> ctypes.pythonapi.PyThread_create_key() 3 >>> ctypes.pythonapi.PyThread_create_key() 4 >>> ctypes.pythonapi.PyThread_delete_key(3) 0 >>> ctypes.pythonapi.PyThread_create_key() 3
msg225390 - (view)	Author: STINNER Victor (vstinner) *	Date: 2014-08-16 12:08
pthread_key_create_overflow.patch: safer patch, delete the newly created key and return an error on integer overflow.
msg225467 - (view)	Author: Roundup Robot (python-dev)	Date: 2014-08-17 20:14
New changeset 1b898b5d5ffe by Victor Stinner in branch 'default': Issue #22206: Using pthread, PyThread_create_key() now sets errno to ENOMEM and http://hg.python.org/cpython/rev/1b898b5d5ffe
msg225468 - (view)	Author: STINNER Victor (vstinner) *	Date: 2014-08-17 20:15
I fixed the issue in Python 3.5, I close the issue. Even if Python 2.7 and 3.4 are also affected, I prefer to not modify them to not take the risk of introducing a regression for a corner case.