Return pointer to Rust struct

01 Cargo.toml

[package]
name = "python-to-rust"
version = "0.0.1"
authors = ["Rob Young"]

[lib]
name = "pytesttype"
crate-type = ["dylib"]

02 src-lib.rs

#![feature(libc)]
#![feature(alloc)]
extern crate libc;
use std::boxed;

pub struct Point {
    x: i64,
    y: i32,
}

#[no_mangle]
pub extern "C" fn start_state() -> *mut Point {
    let point = Box::new(Point{x: 0, y: 10});
    let raw = unsafe { boxed::into_raw(point) };
    println!("{:?}", raw);
    raw
}

#[no_mangle]
pub extern "C" fn continue_state(point: *mut Point) -> i32 {
    println!("{:?}", point);
    let p = unsafe { Box::from_raw(point) };
    println!("{} {}", p.x, p.y);
    0
}

03 src-main.py

import ctypes

lib = ctypes.cdll.LoadLibrary('target/libpytesttype.so')
lib.start_state.restype = ctypes.c_void_p

pointer = lib.start_state()
print("{:x}".format(pointer))
lib.continue_state(pointer)

04 output

0xdc24000
10dc24000
0xdc24000
[1]    64006 segmentation fault  python src/main.py

05 segfault

Process:               Python [62405]
Path:                  /System/Library/Frameworks/Python.framework/Versions/2.7/Resources/Python.app/Contents/MacOS/Python
Identifier:            Python
Version:               2.7.6 (2.7.6)
Code Type:             X86-64 (Native)
Parent Process:        zsh [36342]
Responsible:           iTerm [1189]
User ID:               2016596

PlugIn Path:             /Users/USER/*/libpytesttype-95f1ab493cc8fd06.dylib
PlugIn Identifier:       libpytesttype-95f1ab493cc8fd06.dylib
PlugIn Version:          ??? (0)

Date/Time:             2015-05-08 21:08:12.430 +0100
OS Version:            Mac OS X 10.10.2 (14C1514)
Report Version:        11
Anonymous UUID:        E5968667-05E2-0830-A381-F38ED2164959

Sleep/Wake UUID:       13E59820-ABF2-4557-BBC8-9F60A00B63E8

Time Awake Since Boot: 200000 seconds
Time Since Wake:       9200 seconds

Crashed Thread:        0  Dispatch queue: com.apple.main-thread

Exception Type:        EXC_BAD_ACCESS (SIGSEGV)
Exception Codes:       KERN_INVALID_ADDRESS at 0x0000000010824000

VM Regions Near 0x10824000:
--> 
    __TEXT                 000000010fcc9000-000000010fcca000 [    4K] r-x/rwx SM=COW  /System/Library/Frameworks/Python.framework/Versions/2.7/Resources/Python.app/Contents/MacOS/Python

Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
0   libpytesttype-95f1ab493cc8fd06.dylib	0x000000011012d250 fmt::num::i32.fmt..Display::fmt::h4a85fc9ea099189fytB + 48
1   libpytesttype-95f1ab493cc8fd06.dylib	0x000000011012e54e fmt::write::hec30e83159a50eb8Z7B + 974
2   libpytesttype-95f1ab493cc8fd06.dylib	0x000000011012e179 fmt::Arguments$LT$$u27$a$GT$.Debug::fmt::hcebfc24865089036y5B + 121
3   libpytesttype-95f1ab493cc8fd06.dylib	0x000000011012e54e fmt::write::hec30e83159a50eb8Z7B + 974
4   libpytesttype-95f1ab493cc8fd06.dylib	0x0000000110043715 old_io::Writer::write_fmt::h6008283369114950499 + 197
5   libpytesttype-95f1ab493cc8fd06.dylib	0x0000000110045f26 old_io::stdio::println_args::hb86725cdadc4dc06hKg + 1190
6   libpytesttype-95f1ab493cc8fd06.dylib	0x000000010ffec0d9 continue_state::__rust_abi + 377
7   libpytesttype-95f1ab493cc8fd06.dylib	0x000000010ffebf5a continue_state + 58
8   libffi.dylib                  	0x00007fff9386df44 ffi_call_unix64 + 76
9   libffi.dylib                  	0x00007fff9386e781 ffi_call + 853
10  _ctypes.so                    	0x000000010ffd0762 _ctypes_callproc + 874
11  _ctypes.so                    	0x000000010ffcabad 0x10ffc8000 + 11181
12  org.python.python             	0x000000010fcd82ac PyObject_Call + 99
13  org.python.python             	0x000000010fd54c00 PyEval_EvalFrameEx + 11370
14  org.python.python             	0x000000010fd51d62 PyEval_EvalCodeEx + 1413
15  org.python.python             	0x000000010fd517d7 PyEval_EvalCode + 54
16  org.python.python             	0x000000010fd717bd PyParser_ASTFromFile + 315
17  org.python.python             	0x000000010fd71860 PyRun_FileExFlags + 133
18  org.python.python             	0x000000010fd713fd PyRun_SimpleFileExFlags + 769
19  org.python.python             	0x000000010fd82b23 Py_Main + 3051
20  libdyld.dylib                 	0x00007fff93e855c9 start + 1

Thread 0 crashed with X86 Thread State (64-bit):
  rax: 0x0000000000000000  rbx: 0x00007fff4ff35810  rcx: 0x0000000000000000  rdx: 0x0000000000000000
  rdi: 0x0000000010824000  rsi: 0x00007fff4ff35178  rbp: 0x00007fff4ff35140  rsp: 0x00007fff4ff350a0
   r8: 0x0000000000000004   r9: 0x0000000000000003  r10: 0x0000000000000000  r11: 0x00000000006d3e28
  r12: 0x0000000000000020  r13: 0x0000000000000020  r14: 0x00000001101be740  r15: 0x00007fff4ff35168
  rip: 0x000000011012d250  rfl: 0x0000000000010206  cr2: 0x0000000010824000
  
Logical CPU:     2
Error Code:      0x00000004
Trap Number:     14


Binary Images:
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       0x10fcce000 -        0x10fdbfff7  org.python.python (2.7.6 - 2.7.6) <A5C1B694-31A0-3966-B6BC-C40694DC707F> /System/Library/Frameworks/Python.framework/Versions/2.7/Python
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    0x7fff891e2000 -     0x7fff891e8ff7  libsystem_networkextension.dylib (167.1.10) <29AB225B-D7FB-30ED-9600-65D44B9A9442> /usr/lib/system/libsystem_networkextension.dylib
    0x7fff89dbc000 -     0x7fff89dc1ff7  libsystem_stats.dylib (163.10.18) <9B8CCF24-DDDB-399A-9237-4BEC225D2E8C> /usr/lib/system/libsystem_stats.dylib
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    0x7fff89f4d000 -     0x7fff89f5eff3  libsystem_coretls.dylib (35.10.1) <3EAED90A-7AA0-323C-A52B-E16477981D59> /usr/lib/system/libsystem_coretls.dylib
    0x7fff8a28b000 -     0x7fff8a296fff  libcommonCrypto.dylib (60061) <D381EBC6-69D8-31D3-8084-5A80A32CB748> /usr/lib/system/libcommonCrypto.dylib
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    0x7fff8a78a000 -     0x7fff8a7bafff  libsystem_m.dylib (3086.1) <1E12AB45-6D96-36D0-A226-F24D9FB0D9D6> /usr/lib/system/libsystem_m.dylib
    0x7fff8aef9000 -     0x7fff8af3fff7  libauto.dylib (186) <A260789B-D4D8-316A-9490-254767B8A5F1> /usr/lib/libauto.dylib
    0x7fff8b533000 -     0x7fff8b53aff7  libcompiler_rt.dylib (35) <BF8FC133-EE10-3DA6-9B90-92039E28678F> /usr/lib/system/libcompiler_rt.dylib
    0x7fff8b5fc000 -     0x7fff8b5fcff7  liblaunch.dylib (559.10.3) <DFCDEBDF-8247-3DC7-9879-E7E497DDA4B4> /usr/lib/system/liblaunch.dylib
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    0x7fff90ce2000 -     0x7fff90ceaffb  libcopyfile.dylib (118.1.2) <0C68D3A6-ACDD-3EF3-991A-CC82C32AB836> /usr/lib/system/libcopyfile.dylib
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    0x7fff90f9d000 -     0x7fff90f9dff7  libkeymgr.dylib (28) <77845842-DE70-3CC5-BD01-C3D14227CED5> /usr/lib/system/libkeymgr.dylib
    0x7fff915dc000 -     0x7fff91604fff  libxpc.dylib (559.10.3) <876216DC-D5D3-381E-8AF9-49AE464E5107> /usr/lib/system/libxpc.dylib
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    0x7fff91b22000 -     0x7fff91b23fff  libSystem.B.dylib (1213) <90B107BC-FF74-32CC-B1CF-4E02F544D957> /usr/lib/libSystem.B.dylib
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    0x7fff9386d000 -     0x7fff9386efff  libffi.dylib (18.1) <0F6C6A4D-1210-3585-8DA1-B8A94B9924A5> /usr/lib/libffi.dylib
    0x7fff9386f000 -     0x7fff9388bff7  libsystem_malloc.dylib (53.1.1) <19BCC257-5717-3502-A71F-95D65AFA861B> /usr/lib/system/libsystem_malloc.dylib
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External Modification Summary:
  Calls made by other processes targeting this process:
    task_for_pid: 0
    thread_create: 0
    thread_set_state: 0
  Calls made by this process:
    task_for_pid: 0
    thread_create: 0
    thread_set_state: 0
  Calls made by all processes on this machine:
    task_for_pid: 150162
    thread_create: 0
    thread_set_state: 0

VM Region Summary:
ReadOnly portion of Libraries: Total=85.7M resident=51.5M(60%) swapped_out_or_unallocated=34.1M(40%)
Writable regions: Total=29.2M written=2524K(8%) resident=4448K(15%) swapped_out=0K(0%) unallocated=24.8M(85%)
 
REGION TYPE                      VIRTUAL
===========                      =======
Kernel Alloc Once                     4K
MALLOC                             12.6M
MALLOC (admin)                       16K
STACK GUARD                        56.0M
Stack                              8192K
VM_ALLOCATE                        8208K
__DATA                             1672K
__LINKEDIT                         71.5M
__TEXT                             14.2M
__UNICODE                           544K
shared memory                         4K
===========                      =======
TOTAL                             172.5M

Model: MacBookAir6,2, BootROM MBA61.0099.B18, 2 processors, Intel Core i5, 1.3 GHz, 4 GB, SMC 2.13f15
Graphics: Intel HD Graphics 5000, Intel HD Graphics 5000, Built-In
Memory Module: BANK 0/DIMM0, 2 GB, DDR3, 1600 MHz, 0x80AD, 0x483943434E4E4E384A544D4C41522D4E544D
Memory Module: BANK 1/DIMM0, 2 GB, DDR3, 1600 MHz, 0x80AD, 0x483943434E4E4E384A544D4C41522D4E544D
AirPort: spairport_wireless_card_type_airport_extreme (0x14E4, 0x117), Broadcom BCM43xx 1.0 (7.15.159.13.12)
Bluetooth: Version 4.3.2f6 15235, 3 services, 19 devices, 1 incoming serial ports
Network Service: Wi-Fi, AirPort, en0
Serial ATA Device: APPLE SSD SD0128F, 121.33 GB
USB Device: Internal Memory Card Reader
USB Device: Mass Storage Device
USB Device: BRCM20702 Hub
USB Device: Bluetooth USB Host Controller
Thunderbolt Bus: MacBook Air, Apple Inc., 23.6