Open Radar

 
!!! Resolved in Xcode 8 betas


Summary:
When enabling address sanitizer in a C++ application, a segfault occurs when calling the "store" method of std::atomic. I discovered the problem when debugging my own application and created a simple test case to reproduce it.

Attached is an Xcode project with a main.cpp file that will produce a segfaulting application when compiled with ASAN enabled. I've been able to reproduce the problem by Build&Running inside Xcode with Address Sanitizer enabled in the scheme as well as by compiling the main.cpp file directly with clang.

Steps to Reproduce:
jeremy@Galactus ~/D/A/ASANAtomicBlowup> clang++ -fsanitize=address -std=c++11 -o AtomicBlowup main.cpp
jeremy@Galactus ~/D/A/ASANAtomicBlowup> ./AtomicBlowup 

Expected Results:
Test application should output the following:

Hello, World!

Actual Results:
Test application outputs the following:

ASAN:SIGSEGV
=================================================================
==88426==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000 (pc 0x000106d91796 bp 0x7fff58e6f980 sp 0x7fff58e6f740 T0)
    #0 0x106d91795 in register_wakeup_callback(void (*)(void*), void*) (/Users/jeremy/Desktop/ASANAtomicBlowup/ASANAtomicBlowup/./AtomicBlowup+0x100001795)
    #1 0x106d92040 in main (/Users/jeremy/Desktop/ASANAtomicBlowup/ASANAtomicBlowup/./AtomicBlowup+0x100002040)
    #2 0x7fff8e6605c8 in start (/usr/lib/system/libdyld.dylib+0x35c8)
    #3 0x0  (<unknown module>)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV ??:0 register_wakeup_callback(void (*)(void*), void*)
==88426==ABORTING


Version:
OS X 10.10.5 (14F27)
Xcode Version 7.0 (7A218)
Apple LLVM version 7.0.0 (clang-700.0.72)

Notes:
In my application I worked around the issue by adding "__attribute__((no_sanitize_address))" to the definition of functions that use std::atomic.

Configuration:
MacBook Pro (Retina, 15-inch, Late 2013). Xcode 7.0.0 installed from developer site download section.



//
//  main.cpp
//  ASANAtomicBlowup
//
//  Created by Jeremy Agostino on 10/14/15.
//  Copyright © 2015 JeremyAgost. All rights reserved.
//

#include <iostream>
#include <atomic>

using std::atomic;

struct callback_pair
{
	void (*func)(void*);
	void *arg;
};

atomic<callback_pair> wakeup_callback({nullptr, nullptr});

void register_wakeup_callback(void ( * callback)(void* pVoid), void* param)
{
	wakeup_callback.store({callback, param});
}

void unregister_wakeup_callback()
{
	wakeup_callback.store({nullptr, nullptr});
}

void dummy(void *)
{
	std::cout << "Hello, Dummy!\n";
}

int main(int argc, const char * argv[]) {

	void * fooptr = nullptr;
	register_wakeup_callback(dummy, fooptr);

	unregister_wakeup_callback();

	std::cout << "Hello, World!\n";
    return 0;
}