Created attachment 33882 [details]
self contained program which reproduces the problem

I am sending a sample code with a self contained program which declares a struct called PStruct which contains a variable member which is an atomic of a simple struct.

G++ compiles the code correctly, however it has a segmentation fault in a (IMO) valid atomic exchance operation, when PStruct is allocated using make_shared, but it does not happen when it's allocated using new operator.

In clang 3.5 the code generate a valid program, which runs as expected.

G++ info:

Using built-in specs.
COLLECT_GCC=g++-4.8
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.8/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu 4.8.1-2ubuntu1~12.04' --with-bugurl=file:///usr/share/doc/gcc-4.8/README.Bugs --enable-languages=c,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-4.8 --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.8 --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --enable-gnu-unique-object --enable-plugin --with-system-zlib --disable-browser-plugin --enable-java-awt=gtk --enable-gtk-cairo --with-java-home=/usr/lib/jvm/java-1.5.0-gcj-4.8-amd64/jre --enable-java-home --with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-4.8-amd64 --with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-4.8-amd64 --with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar --enable-objc-gc --enable-multiarch --disable-werror --with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64 --with-tune=generic --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 4.8.1 (Ubuntu 4.8.1-2ubuntu1~12.04)

The command line I am using to compile the code:
$ g++-4.8 -std=c++11 -Wall -Wextra atomic_of_struct_test.cpp -o atomic_of_struct_test -lrt -latomic

The attached file reproduces the problem, because allocates using make_shared. To allocate using new operator, comment line 34 and uncomment line 37.

The expected output in both allocation ways is:
field1: 2, field2: 4

The actual output when compiled with g++ is:
Segmentation fault (core dumped)

The backtrace of the later execution:

#0  0x00007ffff7bd5897 in ?? () from /usr/lib/x86_64-linux-gnu/libatomic.so.1
No symbol table info available.
#1  0x0000000000401186 in std::atomic<TwoFieldStruct>::exchange (this=0x604028, __i=..., _m=std::memory_order_seq_cst) at /usr/include/c++/4.8/atomic:225
        tmp = {
          field1 = 140737488346624, 
          field2 = 4198920
        }
#2  0x00000000004010e3 in PStruct::setMs (this=0x604028, ms=...) at atomic_of_struct_test.cpp:18
No locals.
#3  0x0000000000400f81 in main () at atomic_of_struct_test.cpp:39
        ms = {
          field1 = 2, 
          field2 = 4
        }
        ptr = std::shared_ptr (count 1, weak 0) 0x604028
        oms = {
          field1 = 0, 
          field2 = 4197680
        }