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"please report a bug" -> CompileError with `const fused_t[:, :]` argument #3222

jbrockmendel opened this issue Oct 31, 2019 · 1 comment


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@jbrockmendel jbrockmendel commented Oct 31, 2019

Looking at pandas._libs.algos.diff_2d (, the current declaration is:

def diff_2d(ndarray[diff_t, ndim=2] arr, [out_t, ndim=2] out, Py_ssize_t periods, int axis):

where diff_t and out_t are fused types (all numeric, defined just above the function in the link above). To avoid build warnings, I want to change the ndarray[diff_t, ndim=2] arr to const diff_t[:, :] arr. Doing this without the const works fine, but with the const, I get compile-time error:

def diff_2d(const diff_t[:, :] arr,

pandas/_libs/algos_common_helper.pxi:22:25: Compiler crash in AnalyseDeclarationsTransform

File '', line 124, in analyse_declarations: ModuleNode(algos.pyx:1:0,
    full_module_name = 'pandas._libs.algos')
File '', line 431, in analyse_declarations: StatListNode(algos.pyx:1:0)
File '', line 431, in analyse_declarations: StatListNode(algos_common_helper.pxi:1:0)
File '', line 375, in analyse_declarations: CompilerDirectivesNode(algos_common_helper.pxi:22:0)
File '', line 431, in analyse_declarations: StatListNode(algos_common_helper.pxi:22:0)
File '', line 2887, in analyse_declarations: DefNode(algos_common_helper.pxi:22:0,
    modifiers = [...]/0,
    name = 'diff_2d',
    num_required_args = 4,
    outer_attrs = [...]/2,
    py_wrapper_required = True,
    reqd_kw_flags_cname = '0')
File '', line 2925, in analyse_argument_types: DefNode(algos_common_helper.pxi:22:0,
    modifiers = [...]/0,
    name = 'diff_2d',
    num_required_args = 4,
    outer_attrs = [...]/2,
    py_wrapper_required = True,
    reqd_kw_flags_cname = '0')
File '', line 1093, in analyse: MemoryViewSliceTypeNode(algos_common_helper.pxi:22:25,
    name = 'memoryview')

Compiler crash traceback from this point on:
  File "/usr/local/lib/python3.7/site-packages/Cython/Compiler/", line 1093, in analyse
    self.type = PyrexTypes.MemoryViewSliceType(base_type, axes_specs)
  File "/usr/local/lib/python3.7/site-packages/Cython/Compiler/", line 625, in __init__
    self.dtype_name = Buffer.mangle_dtype_name(self.dtype)
  File "/usr/local/lib/python3.7/site-packages/Cython/Compiler/", line 631, in mangle_dtype_name
    return prefix + dtype.specialization_name()
  File "/usr/local/lib/python3.7/site-packages/Cython/Compiler/", line 57, in specialization_name
    common_subs = (self.empty_declaration_code()
  File "/usr/local/lib/python3.7/site-packages/Cython/Compiler/", line 51, in empty_declaration_code
    self._empty_declaration = self.declaration_code('')
  File "/usr/local/lib/python3.7/site-packages/Cython/Compiler/", line 1582, in declaration_code
    return self.const_base_type.declaration_code("const %s" % entity_code, for_display, dll_linkage, pyrex)
  File "/usr/local/lib/python3.7/site-packages/Cython/Compiler/", line 1649, in declaration_code
    raise Exception("This may never happen, please report a bug")
Exception: This may never happen, please report a bug
Traceback (most recent call last):
  File "", line 809, in <module>
    ext_modules=maybe_cythonize(extensions, compiler_directives=directives),
  File "", line 538, in maybe_cythonize
    return cythonize(extensions, *args, **kwargs)
  File "/usr/local/lib/python3.7/site-packages/Cython/Build/", line 1096, in cythonize
  File "/usr/local/lib/python3.7/site-packages/Cython/Build/", line 1219, in cythonize_one
    raise CompileError(None, pyx_file)
Cython.Compiler.Errors.CompileError: pandas/_libs/algos.pyx

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@da-woods da-woods commented Oct 31, 2019

For what it's worth my pull request #3205 appears to fix this too, although I haven't investigated why.

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