I'm trying to call a function in a C library with two args, a pointer and an int, and was seeing the C function segfault. When I break on the C function in GDB, I see that the pointer I passed in the first argument from Rust shows up in the second argument, and there's another address added as the first argument.
Simplified to a minimal example by passing a constant for the pointer to show that it's shifted into the second argument:
libusb_set_debug(10 as *mut libusb_context, 4);
/* Breakpoint 1, libusb_set_debug (ctx=0x804e738, level=10) at core.c:1600 */
I'm using Fedora 18, 32-bit
rustc 0.7 (3e933b1 2013-07-06 08:32:10 -0700)
host: i686-unknown-linux-gnu
Here's the original code and GDB output:
use std::cast;
use std::libc::{c_void, c_int, size_t, malloc, free};
use std::ptr;
use std::unstable::intrinsics;
struct libusb_context;
#[link_args = "-lusb-1.0"]
extern{
fn libusb_init(ctx: **mut libusb_context) -> c_int;
fn libusb_exit(ctx: *mut libusb_context) -> c_void;
fn libusb_set_debug(ctx: *mut libusb_context, level: c_int) -> c_void;
}
fn main() {
unsafe{
let mut ctx: *mut libusb_context = intrinsics::init();
let r = libusb_init(&ctx);
println(fmt!("r=%?, ctx=0x%x", r, ctx as uint));
libusb_set_debug(ctx, 4);
println("set debug");
}
}
/*
r=0, ctx=0xb7a00468
[Switching to Thread 0xb7bffb40 (LWP 32527)]
Breakpoint 1, libusb_set_debug (ctx=0x805b690, level=-1214249880)
at core.c:1600
1600 {
(gdb) p/x level
$1 = 0xb7a00468
*/
I also tried calling libusb_exit(ctx), and it also receives the wrong pointer and segfaults.
I'm trying to call a function in a C library with two args, a pointer and an int, and was seeing the C function segfault. When I break on the C function in GDB, I see that the pointer I passed in the first argument from Rust shows up in the second argument, and there's another address added as the first argument.
Simplified to a minimal example by passing a constant for the pointer to show that it's shifted into the second argument:
I'm using Fedora 18, 32-bit
rustc 0.7 (3e933b1 2013-07-06 08:32:10 -0700)
host: i686-unknown-linux-gnu
Here's the original code and GDB output:
I also tried calling
libusb_exit(ctx), and it also receives the wrong pointer and segfaults.