i386 test failure in test_scipy: TestScikitImage.test__greyreconstruct: different signedness: ‘long unsigned int’ and ‘long int’

[drew-parsons]

Pythran 0.10.0 tests fail on 32-bit i386 (i686), in test_scipy: TestScikitImage.test__greyreconstruct.
A test log can be found at https://ci.debian.net/data/autopkgtest/testing/i386/p/pythran/20587303/log.gz

The toplevel error is

test_scipy.py .................F..............                           [100%]

=================================== FAILURES ===================================
_________________ TestScikitImage.test__greyreconstruct_norun0 _________________

attrs = {'cmdclass': {'bdist_rpm': <class 'numpy.distutils.command.bdist_rpm.bdist_rpm'>, 'build': <class 'numpy.distutils.com...t.PythranExtension('_greyreconstruct_norun00') at 0xf11943a0>], 'headers': [], 'name': '_greyreconstruct_norun00', ...}
klass = <class 'numpy.distutils.numpy_distribution.NumpyDistribution'>
dist = <numpy.distutils.numpy_distribution.NumpyDistribution object at 0xf11947d8>
ok = True

    def setup (**attrs):
        """The gateway to the Distutils: do everything your setup script needs
        to do, in a highly flexible and user-driven way....

The underlying error message seems to be:

----------------------------- Captured stderr call -----------------------------
In file included from /usr/lib/python3/dist-packages/pythran/pythonic/types/numpy_operators.hpp:12,
                 from /usr/lib/python3/dist-packages/pythran/pythonic/types/ndarray.hpp:1303,
                 from /usr/lib/python3/dist-packages/pythran/pythonic/types/tuple.hpp:13,
                 from /usr/lib/python3/dist-packages/pythran/pythonic/builtins/bool_.hpp:7,
                 from /usr/lib/python3/dist-packages/pythran/pythonic/types/NoneType.hpp:8,
                 from /usr/lib/python3/dist-packages/pythran/pythonic/types/slice.hpp:5,
                 from /usr/lib/python3/dist-packages/pythran/pythonic/core.hpp:36,
                 from /tmp/tmp5yei6hk8.cpp:1:
/usr/lib/python3/dist-packages/pythran/pythonic/operator_/eq.hpp: In instantiation of ‘decltype ((forward<A>(a) == forward<B>(b))) {anonymous}::pythonic::operator_::eq(A&&, B&&) [with A = long unsigned int&; B = long int; decltype ((forward<A>(a) == forward<B>(b))) = bool]’:
/tmp/tmp5yei6hk8.cpp:156:36:   required from ‘typename __pythran__greyreconstruct_norun00::reconstruction_loop::type<argument_type0, argument_type1, argument_type2, argument_type3, argument_type4, argument_type5>::result_type __pythran__greyreconstruct_norun00::reconstruction_loop::operator()(argument_type0&&, argument_type1&&, argument_type2&&, argument_type3&&, argument_type4&&, argument_type5&&) const [with argument_type0 = {anonymous}::pythonic::types::ndarray<long unsigned int, {anonymous}::pythonic::types::pshape<long int> >&; argument_type1 = {anonymous}::pythonic::types::ndarray<long int, {anonymous}::pythonic::types::pshape<long int> >&; argument_type2 = {anonymous}::pythonic::types::ndarray<long int, {anonymous}::pythonic::types::pshape<long int> >&; argument_type3 = {anonymous}::pythonic::types::ndarray<long int, {anonymous}::pythonic::types::pshape<long int> >&; argument_type4 = int&; argument_type5 = int&; typename __pythran__greyreconstruct_norun00::reconstruction_loop::type<argument_type0, argument_type1, argument_type2, argument_type3, argument_type4, argument_type5>::result_type = {anonymous}::pythonic::types::none_type]’
/tmp/tmp5yei6hk8.cpp:220:101:   required from here
/usr/lib/python3/dist-packages/pythran/pythonic/operator_/eq.hpp:15:31: error: comparison of integer expressions of different signedness: ‘long unsigned int’ and ‘long int’ [-Werror=sign-compare]
   15 |     return std::forward<A>(a) == std::forward<B>(b);
      |            ~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~
cc1plus: note: unrecognized command-line option ‘-Wno-unknown-warning-option’ may have been intended to silence earlier diagnostics
cc1plus: note: unrecognized command-line option ‘-Wno-unknown-warning-option’ may have been intended to silence earlier diagnostics
cc1plus: all warnings being treated as errors
WARNING: Compilation error, trying hard to find its origin...
WARNING: Nop, I'm going to flood you with C++ errors!

pythran appears to be trying to compare a ‘long unsigned int’ against a ‘long int’ . It's not obvious to me which line in pythran/tests/scikit-image/_greyreconstruct.py (or elsewhere) is triggering it.

[serge-sans-paille]

Can you confirm the following fixes the warning:

diff --git a/pythran/tests/scikit-image/_greyreconstruct.py b/pythran/tests/scikit-image/_greyreconstruct.py
index 5ac48f0..56ab6c3 100644
--- a/pythran/tests/scikit-image/_greyreconstruct.py
+++ b/pythran/tests/scikit-image/_greyreconstruct.py
@@ -45,7 +45,7 @@ def reconstruction_loop(ranks, prev, next, strides, current_idx, image_stride):
     while current_idx != -1:
         if current_idx < image_stride:
             current_rank = ranks[current_idx]
-            if current_rank == 0:
+            if not current_rank:
                 break
             for i in range(nstrides):
                 neighbor_idx = current_idx + strides[i]

[drew-parsons]

i386 seems to pass fine with the patch, thanks @serge-sans-paille