Bug 1473425

Could you provide a minimal example of a program to compile with those macros?

Also this certainly looks like a good candidate for an upstream pull request.

Created attachment 1302514 [details]
file on which warning emitted with -Wall

compile with "gcc -Wall -I/usr/include/python2.7 -c netnsmodule.c"

On F26, this emits the warning described earlier.

The file is part of the CORE network simulator (https://github.com/coreemu/core). I'm trying to build it as an RPM package using mock, a process that results in "-Wall -Werror" being specified on the gcc command line, which makes the rpm build process fail.

So this is due to the new warning [0] with gcc 7:

-Wint-in-bool-context warns about suspicious uses of integer values where boolean values are expected. This warning is enabled by -Wall.

[0] https://gcc.gnu.org/gcc-7/changes.html

This should be addressed upstream first preferably. Would be you be able to open a new issue at http://bugs.python.org/ ? Maybe sent a pull request?

I can guide you through the procedures if required or I can take over at any step you'd prefer.

http://bugs.python.org/issue31013

This bug appears to have been reported against 'rawhide' during the Fedora 27 development cycle.
Changing version to '27'.

I'm getting the same error when trying to compile CORE Network Emulator (https://github.com/coreemu/core) with gcc7 on Fedora 26:

gcc -pthread -fno-strict-aliasing -O2 -g -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -m64 -mtune=generic -D_GNU_SOURCE -fPIC -fwrapv -DNDEBUG -O2 -g -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -m64 -mtune=generic -D_GNU_SOURCE -fPIC -fwrapv -O3 -Werror -Wall -D_GNU_SOURCE -fPIC -I/usr/include/python2.7 -c netnsmodule.c -o build/temp.linux-x86_64-2.7/netnsmodule.o
In file included from /usr/include/python2.7/Python.h:78:0,
                 from netnsmodule.c:16:
netnsmodule.c: In function ‘netns_nsexecvp’:
/usr/include/python2.7/pymem.h:97:30: error: ‘*’ in boolean context, suggest ‘&&’ instead [-Werror=int-in-bool-context]
  ( (type *) PyMem_MALLOC((n) * sizeof(type)) ) )
                              ^
/usr/include/python2.7/pymem.h:75:15: note: in definition of macro ‘PyMem_MALLOC’
     : malloc((n) ? (n) : 1))
               ^
netnsmodule.c:61:10: note: in expansion of macro ‘PyMem_NEW’
   argv = PyMem_NEW(char *, argc + 1);
          ^~~~~~~~~
cc1: all warnings being treated as errors
error: command 'gcc' failed with exit status 1
make[3]: *** [Makefile:695: libnetns.a] Error 1
make[3]: Leaving directory '/home/user/Downloads/core/daemon/src'
make[2]: *** [Makefile:637: all-recursive] Error 1
make[2]: Leaving directory '/home/user/Downloads/core/daemon'
make[1]: *** [Makefile:459: all-recursive] Error 1
make[1]: Leaving directory '/home/user/Downloads/core'
make: *** [Makefile:387: all] Error 2

Solved in https://github.com/python/cpython/pull/3581 and should be part of Python 2.7.15
I'll prepare a backport for Fedora.

python2-2.7.14-8.fc27 has been submitted as an update to Fedora 27. https://bodhi.fedoraproject.org/updates/FEDORA-2018-76e9d22b5c

Fixed in Rawhide and Fedora 28. For f27, please test and add karma :)
https://bodhi.fedoraproject.org/updates/FEDORA-2018-76e9d22b5c

python2-2.7.14-8.fc27 has been pushed to the Fedora 27 testing repository. If problems still persist, please make note of it in this bug report.
See https://fedoraproject.org/wiki/QA:Updates_Testing for
instructions on how to install test updates.
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2018-76e9d22b5c

python2-2.7.14-8.fc27 has been pushed to the Fedora 27 stable repository. If problems still persist, please make note of it in this bug report.