MAINT: remove relaxed strides debug build setting

This follows up on gh-21039. As noted there, this doesn't really serve any purpose anymore and historically seems to have resulted in only 2 bug reports.
numpy · charris · Sep 15, 2023 · Sep 15, 2023 · Sep 15, 2023 · 94b9f2a78733d322cea8fd02c76c39beecb11aec
commit 94b9f2a78733d322cea8fd02c76c39beecb11aec
diff --git a/.github/workflows/linux.yml b/.github/workflows/linux.yml
@@ -3,7 +3,7 @@ name: Linux tests
 # This file is meant for testing across supported Python versions, build types
 # and interpreters (PyPy, python-dbg, a pre-release Python in summer time),
 # build-via-sdist, run benchmarks, measure code coverage, and other build
-# options like relaxed-strides.
+# options.
 
 on:
   push:
@@ -172,24 +172,6 @@ jobs:
       run: |
         spin bench --quick
 
-  relaxed_strides_debug:
-    needs: [smoke_test]
-    runs-on: ubuntu-latest
-    if: github.event_name != 'push'
-    env:
-      CHECK_BLAS: 1
-      NPY_USE_BLAS_ILP64: 1
-      NPY_RELAXED_STRIDES_DEBUG: 1
-    steps:
-    - uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4.0.0
-      with:
-        submodules: recursive
-        fetch-depth: 0
-    - uses: actions/setup-python@61a6322f88396a6271a6ee3565807d608ecaddd1 # v4.7.0
-      with:
-        python-version: '3.11'
-    - uses: ./.github/actions
-
   sdist:
     needs: [smoke_test]
     runs-on: ubuntu-latest

diff --git a/doc/release/upcoming_changes/24717.change.rst b/doc/release/upcoming_changes/24717.change.rst
@@ -0,0 +1,3 @@
+The "relaxed strides" debug build option, which was previously enabled through
+the ``NPY_RELAXED_STRIDES_DEBUG`` environment variable or the
+``-Drelaxed-strides-debug`` config-settings flag, has been removed.
diff --git a/doc/source/reference/arrays.ndarray.rst b/doc/source/reference/arrays.ndarray.rst
@@ -167,9 +167,6 @@ base offset itself is a multiple of `self.itemsize`. Understanding
     for C-style contiguous arrays or ``self.strides[0] == self.itemsize`` for
     Fortran-style contiguous arrays is true.
 
-    ``NPY_RELAXED_STRIDES_DEBUG=1`` can be used to help find errors when
-    incorrectly relying on the strides in C-extension code (see below warning).
-
 Data in new :class:`ndarrays <ndarray>` is in the :term:`row-major` (C)
 order, unless otherwise specified, but, for example, :ref:`basic
 array slicing <arrays.indexing>` often produces :term:`views <view>`

diff --git a/doc/source/reference/global_state.rst b/doc/source/reference/global_state.rst
@@ -59,20 +59,6 @@ See :ref:`runtime-simd-dispatch`.
 Debugging-related options
 =========================
 
-Relaxed strides checking
-------------------------
-
-The *compile-time* environment variable::
-
-    NPY_RELAXED_STRIDES_DEBUG=0
-
-can be set to help debug code written in C which iterators through arrays
-manually.  When an array is contiguous and iterated in a contiguous manner,
-its ``strides`` should not be queried.  This option can help find errors where
-the ``strides`` are incorrectly used.
-For details see the :ref:`memory layout <memory-layout>` documentation.
-
-
 Warn if no memory allocation policy when deallocating data
 ----------------------------------------------------------
 
@@ -84,4 +70,4 @@ be emitted. A better alternative is to use a ``PyCapsule`` with a deallocator
 and set the ``ndarray.base``.
 
 .. versionchanged:: 1.25.2
-    This variable is only checked on the first import.
+    This variable is only checked on the first import.
diff --git a/meson_options.txt b/meson_options.txt
@@ -29,5 +29,3 @@ option('test-simd', type: 'array',
         description: 'Specify a list of CPU features to be tested against NumPy SIMD interface')
 option('test-simd-args', type: 'string', value: '',
         description: 'Extra args to be passed to the `_simd` module that is used for testing the NumPy SIMD interface')
-option('relaxed-strides-debug', type: 'boolean', value: false,
-        description: 'Enable relaxed strides debug mode (see `NPY_RELAXED_STRIDES_DEBUG` docs)')
diff --git a/numpy/_pytesttester.py b/numpy/_pytesttester.py
@@ -37,8 +37,6 @@ def _show_numpy_info():
     import numpy as np
 
     print("NumPy version %s" % np.__version__)
-    relaxed_strides = np.ones((10, 1), order="C").flags.f_contiguous
-    print("NumPy relaxed strides checking option:", relaxed_strides)
     info = np.lib._utils_impl._opt_info()
     print("NumPy CPU features: ", (info if info else 'nothing enabled'))
 

diff --git a/numpy/core/config.h.in b/numpy/core/config.h.in
@@ -94,7 +94,6 @@
 #mesondefine HAVE_CTANHL
 
 #mesondefine NPY_CAN_LINK_SVML
-#mesondefine NPY_RELAXED_STRIDES_DEBUG
 
 #mesondefine HAVE_LDOUBLE_INTEL_EXTENDED_16_BYTES_LE
 #mesondefine HAVE_LDOUBLE_INTEL_EXTENDED_12_BYTES_LE

diff --git a/numpy/core/meson.build b/numpy/core/meson.build
@@ -478,10 +478,6 @@ endif
 # TODO: document this (search for NPY_NOSMP in C API docs)
 cdata.set10('NPY_NO_SMP', get_option('disable-threading'))
 
-# Use bogus stride debug aid to flush out bugs where users use strides of
-# dimensions with length 1 to index a full contiguous array.
-cdata.set10('NPY_RELAXED_STRIDES_DEBUG', get_option('relaxed-strides-debug'))
-
 # Check whether we can use inttypes (C99) formats
 if cc.has_header_symbol('inttypes.h', 'PRIdPTR')
   cdata.set10('NPY_USE_C99_FORMATS', true)

diff --git a/numpy/core/numeric.py b/numpy/core/numeric.py
@@ -487,10 +487,8 @@ def isfortran(a):
     """
     Check if the array is Fortran contiguous but *not* C contiguous.
 
-    This function is obsolete and, because of changes due to relaxed stride
-    checking, its return value for the same array may differ for versions
-    of NumPy >= 1.10.0 and previous versions. If you only want to check if an
-    array is Fortran contiguous use ``a.flags.f_contiguous`` instead.
+    This function is obsolete. If you only want to check if an array is Fortran
+    contiguous use ``a.flags.f_contiguous`` instead.
 
     Parameters
     ----------

diff --git a/numpy/core/src/multiarray/ctors.c b/numpy/core/src/multiarray/ctors.c
@@ -3971,10 +3971,9 @@ PyArray_FromIter(PyObject *obj, PyArray_Descr *dtype, npy_intp count)
         }
         ((PyArrayObject_fields *)ret)->data = new_data;
    
-        if (count < 0 || NPY_RELAXED_STRIDES_DEBUG) {
+        if (count < 0) {
             /*
-             * If the count was smaller than zero or NPY_RELAXED_STRIDES_DEBUG
-             * was active, the strides may be all 0 or intentionally mangled
+             * If the count was smaller than zero, the strides may be all 0
              * (even in the later dimensions for `count < 0`!
              * Thus, fix all strides here again for C-contiguity.
              */
@@ -4047,12 +4046,6 @@ _array_fill_strides(npy_intp *strides, npy_intp const *dims, int nd, size_t item
             else {
                 not_cf_contig = 0;
             }
-#if NPY_RELAXED_STRIDES_DEBUG
-            /* For testing purpose only */
-            if (dims[i] == 1) {
-                strides[i] = NPY_MAX_INTP;
-            }
-#endif /* NPY_RELAXED_STRIDES_DEBUG */
         }
         if (not_cf_contig) {
             *objflags = ((*objflags)|NPY_ARRAY_F_CONTIGUOUS) &
@@ -4071,12 +4064,6 @@ _array_fill_strides(npy_intp *strides, npy_intp const *dims, int nd, size_t item
             else {
                 not_cf_contig = 0;
             }
-#if NPY_RELAXED_STRIDES_DEBUG
-            /* For testing purpose only */
-            if (dims[i] == 1) {
-                strides[i] = NPY_MAX_INTP;
-            }
-#endif /* NPY_RELAXED_STRIDES_DEBUG */
         }
         if (not_cf_contig) {
             *objflags = ((*objflags)|NPY_ARRAY_C_CONTIGUOUS) &

diff --git a/numpy/core/src/multiarray/textreading/rows.c b/numpy/core/src/multiarray/textreading/rows.c
@@ -297,12 +297,7 @@ read_rows(stream *s,
                  */
                 data_array = (PyArrayObject *)PyArray_SimpleNewFromDescr(
                         ndim, result_shape, out_descr);
-#ifdef NPY_RELAXED_STRIDES_DEBUG
-                /* Incompatible with NPY_RELAXED_STRIDES_DEBUG due to growing */
-                if (result_shape[0] == 1) {
-                    PyArray_STRIDES(data_array)[0] = row_size;
-                }
-#endif /* NPY_RELAXED_STRIDES_DEBUG */
+
                 if (data_array == NULL) {
                     goto error;
                 }

diff --git a/numpy/core/tests/test_multiarray.py b/numpy/core/tests/test_multiarray.py
@@ -3520,8 +3520,6 @@ def test_ravel(self):
         # 1-element tidy strides test:
         a = np.array([[1]])
         a.strides = (123, 432)
-        # If the following stride is not 8, NPY_RELAXED_STRIDES_DEBUG is
-        # messing them up on purpose:
         if np.ones(1).strides == (8,):
             assert_(np.may_share_memory(a.ravel('K'), a))
             assert_equal(a.ravel('K').strides, (a.dtype.itemsize,))
@@ -8032,9 +8030,7 @@ def test_export_record(self):
             assert_equal(y.format, 'T{b:a:=h:b:i:c:l:d:q:dx:B:e:@H:f:=I:g:L:h:Q:hx:f:i:d:j:^g:k:=Zf:ix:Zd:jx:^Zg:kx:4s:l:=4w:m:3x:n:?:o:@e:p:}')
         else:
             assert_equal(y.format, 'T{b:a:=h:b:i:c:q:d:q:dx:B:e:@H:f:=I:g:Q:h:Q:hx:f:i:d:j:^g:k:=Zf:ix:Zd:jx:^Zg:kx:4s:l:=4w:m:3x:n:?:o:@e:p:}')
-        # Cannot test if NPY_RELAXED_STRIDES_DEBUG changes the strides
-        if not (np.ones(1).strides[0] == np.iinfo(np.intp).max):
-            assert_equal(y.strides, (sz,))
+        assert_equal(y.strides, (sz,))
         assert_equal(y.itemsize, sz)
 
     def test_export_subarray(self):
@@ -8143,23 +8139,6 @@ def test_relaxed_strides(self, c=np.ones((1, 10, 10), dtype='i8')):
                     arr, ['C_CONTIGUOUS'])
             assert_(strides[-1] == 8)
 
-    @pytest.mark.valgrind_error(reason="leaks buffer info cache temporarily.")
-    @pytest.mark.skipif(not np.ones((10, 1), order="C").flags.f_contiguous,
-            reason="Test is unnecessary (but fails) without relaxed strides.")
-    def test_relaxed_strides_buffer_info_leak(self, arr=np.ones((1, 10))):
-        """Test that alternating export of C- and F-order buffers from
-        an array which is both C- and F-order when relaxed strides is
-        active works.
-        This test defines array in the signature to ensure leaking more
-        references every time the test is run (catching the leak with
-        pytest-leaks).
-        """
-        for i in range(10):
-            _, s = _multiarray_tests.get_buffer_info(arr, ['F_CONTIGUOUS'])
-            assert s == (8, 8)
-            _, s = _multiarray_tests.get_buffer_info(arr, ['C_CONTIGUOUS'])
-            assert s == (80, 8)
-
     def test_out_of_order_fields(self):
         dt = np.dtype(dict(
             formats=['<i4', '<i4'],
@@ -9788,8 +9767,6 @@ def test_uintalignment_and_alignment():
 class TestAlignment:
     # adapted from scipy._lib.tests.test__util.test__aligned_zeros
     # Checks that unusual memory alignments don't trip up numpy.
-    # In particular, check RELAXED_STRIDES don't trip alignment assertions in
-    # NDEBUG mode for size-0 arrays (gh-12503)
 
     def check(self, shape, dtype, order, align):
         err_msg = repr((shape, dtype, order, align))

diff --git a/numpy/core/tests/test_regression.py b/numpy/core/tests/test_regression.py
@@ -644,10 +644,6 @@ def test_reshape_zero_size(self):
         a = np.ones((0, 2))
         a.shape = (-1, 2)
 
-    # Cannot test if NPY_RELAXED_STRIDES_DEBUG changes the strides.
-    # With NPY_RELAXED_STRIDES_DEBUG the test becomes superfluous.
-    @pytest.mark.skipif(np.ones(1).strides[0] == np.iinfo(np.intp).max,
-                        reason="Using relaxed stride debug")
     def test_reshape_trailing_ones_strides(self):
         # GitHub issue gh-2949, bad strides for trailing ones of new shape
         a = np.zeros(12, dtype=np.int32)[::2]  # not contiguous
@@ -904,17 +900,6 @@ def test_copy_detection_corner_case(self):
         # Ticket #658
         np.indices((0, 3, 4)).T.reshape(-1, 3)
 
-    # Cannot test if NPY_RELAXED_STRIDES_DEBUG changes the strides.
-    # With NPY_RELAXED_STRIDES_DEBUG the test becomes superfluous,
-    # 0-sized reshape itself is tested elsewhere.
-    @pytest.mark.skipif(np.ones(1).strides[0] == np.iinfo(np.intp).max,
-                        reason="Using relaxed stride debug")
-    def test_copy_detection_corner_case2(self):
-        # Ticket #771: strides are not set correctly when reshaping 0-sized
-        # arrays
-        b = np.indices((0, 3, 4)).T.reshape(-1, 3)
-        assert_equal(b.strides, (3 * b.itemsize, b.itemsize))
-
     def test_object_array_refcounting(self):
         # Ticket #633
         if not hasattr(sys, 'getrefcount'):