[Cython] Cython-0.17 builtin type import bug

[Robert Byrnes]

If a builtin type that differs between Python 2 and 3 (e.g., unicode)
is imported, then malformed C code is emitted by Cython-0.17: there is
an extraneous, unbalanced #if.

Here's a small reproducer:

shell$ cat foo.pyx
cdef extern from "Python.h":
ctypedef class __builtin__.unicode [object PyUnicodeObject]:
pass

shell$ cython foo.pyx
warning: foo.pyx:2:4: unicode already a builtin Cython type

shell$ gcc -c -fPIC -I/usr/include/python2.6 foo.c
foo.c:5:1: error: unterminated #else
foo.c: In function 'initfoo':
foo.c:574: error: expected declaration or statement at end of input
foo.c:535: error: label '__pyx_L1_error' used but not defined

This works for Cython-0.16 and earlier.

I think this was broken by ...

https://github.com/cython/cython/commit/558f4ef1c48ce091fa15b9319eb0f92cd4758f09

This patch for ModuleNode.generate_type_import_call seems to fix it:

--- a/Cython/Compiler/ModuleNode.py
+++ b/Cython/Compiler/ModuleNode.py
@@ -2281,7 +2281,6 @@ class ModuleNode(Nodes.Node, Nodes.BlockNode):
 module_name = '__Pyx_BUILTIN_MODULE_NAME'
 if type.name in Code.non_portable_builtins_map:
 condition, replacement = 
Code.non_portable_builtins_map[type.name]
-code.putln("#if %s" % condition)
 if objstruct in Code.basicsize_builtins_map:
 # Some builtin types have a tp_basicsize which differs from 
sizeof(...):
 sizeof_objstruct = Code.basicsize_builtins_map[objstruct]

Thanks,

--
Bob
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[Cython] assignment to reference argument bug, revisited

[Robert Byrnes]

Are there any plans to fix the "Assignment to reference" bug mentioned here?

https://groups.google.com/forum/?fromgroups=#!topic/cython-users/j58Sp3QMrD4

> Oh, yes, of course. Good old C++, where local T& x is unassignable but
> assigning to an argument T& x is a common idiom. This is a bug in Cython.

This is still broken in 0.19.2, and a casual inspection of 0.20rc1
suggests that it is broken there as well.

Is the fix as simple as this?

--- ExprNodes.py~   2014-01-16 12:31:08.377573000 -0500
+++ ExprNodes.py2014-01-16 12:30:56.945501000 -0500
@@ -1605,7 +1605,7 @@ class NameNode(AtomicExprNode):

 if self.type.is_const:
 error(self.pos, "Assignment to const '%s'" % self.name)
-if self.type.is_reference:
+if self.type.is_reference and not self.entry.is_arg:
 error(self.pos, "Assignment to reference '%s'" % self.name)
 if not self.is_lvalue():
 error(self.pos, "Assignment to non-lvalue '%s'"

This seems to work for me, but ...

I wonder if it is also correct to set self.entry.cf_unused = True
for the case of assignment to reference arguments, to avoid CYTHON_UNUSED
annotations in the function definitions and unused variable warnings.

--
Bob


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