I have this Cython code:

cdef struct MyStruct:
    int x
 
def byte_bugginess(x=1):
    cdef char val = 1
    cdef MyStruct foo
 
    print("1 - val = %d" % val)
 
    if x in (3, 4):
        print("2 - val = %d" % val)
        val = 2
        print("3 - val = %d" % val)
    else:
        print("4 - val = %d" % val)
        val = foo.x
        print("5 - val = %d" % val)
 
    print("6 - val = %d" % val)

and the output is:

marca@marca-mac:~/dev/git-repos/cython-test$ make
python setup.py build_ext --inplace
running build_ext
gcc-4.2 not found, using clang instead
cythoning hello.pyx to hello.c
building 'hello' extension
creating build
creating build/temp.macosx-10.6-intel-2.7
clang -fno-strict-aliasing -fno-common -dynamic -isysroot /Developer/SDKs/MacOSX10.6.sdk -arch i386 -arch x86_64 -g -O2 -DNDEBUG -g -O3 -I/Library/Frameworks/Python.framework/Versions/2.7/include/python2.7 -c hello.c -o build/temp.macosx-10.6-intel-2.7/hello.o
clang -bundle -undefined dynamic_lookup -arch i386 -arch x86_64 -isysroot /Developer/SDKs/MacOSX10.6.sdk -isysroot /Developer/SDKs/MacOSX10.6.sdk -g build/temp.macosx-10.6-intel-2.7/hello.o -o /Users/marca/dev/git-repos/cython-test/hello.so
python -c 'import hello; hello.byte_bugginess(1)'
1 - val = 1
4 - val = 1
5 - val = 0
6 - val = 2

How could val be equal to 2? This implies that the false clause of the if statement is getting evaluated?

Weird.

Full code is at this gist.

I posted about this to the cython-users Google group. I am curious to see what they say.