ctype C library call always returns 0 with Python3

[Nobody]

On Sat, 19 May 2012 11:30:46 +0200, Johannes Bauer wrote:

> import ctypes
> libc = ctypes.cdll.LoadLibrary("/lib64/libc-2.14.1.so")
> print(libc.strchr("abcdef", ord("d")))

In 3.x, a string will be passed as a wchar_t*, not a char*. IOW, the
memory pointed to by the first argument to strchr() will consist mostly of
NUL bytes.

Either use a "bytes" instead of a string:

	> print(libc.strchr(b"abcdef", ord("d")))
	1984444291

or specify the argument types to force a conversion:

	> libc.strchr.argtypes = [c_char_p, c_int]
	> print(libc.strchr("abcdef", ord("d")))
	1984755787