This problem is found when writing some code related to computer graphics, a simplified version of the code is shown below:
#include <bits/stdc .h>
#define __AVX__ 1
#define __AVX2__ 1
#pragma GCC target("avx,avx2,popcnt,tune=native")
#include <immintrin.h>
namespace with_avx {
class vec {
public:
vec(double x = 0, double y = 0, double z = 0, double t = 0) {
vec_data = _mm256_set_pd(t, z, y, x);
}
__m256d vec_data;
};
} // namespace with_avx
namespace without_avx {
class vec {
public:
vec(double x = 0, double y = 0, double z = 0, double t = 0) {
vec_data[0] = x, vec_data[1] = y, vec_data[2] = z, vec_data[3] = t;
}
double vec_data[4];
};
} // namespace without_avx
#ifdef USE_AVX
using namespace with_avx;
#else
using namespace without_avx;
#endif
vec same(vec x) { return x; }
std::function<vec(vec)> stdfunc = same;
int main() {
vec rand_vec(rand(), rand(), rand());
vec ret = stdfunc(rand_vec);
std::cout<<(double)ret.vec_data[0];
}
If I compile the code with the flag USE_AVX
like the following:
g -12 stdfunction_test.cpp -o ../build/unit_test -D USE_AVX -g
g will output some warnings:
In file included from /usr/include/c /12/functional:59,
from /usr/include/x86_64-linux-gnu/c /12/bits/stdc .h:71,
from stdfunction_test.cpp:2:
/usr/include/c /12/bits/std_function.h: In member function ‘_Res std::function<_Res(_ArgTypes ...)>::operator()(_ArgTypes ...) const [with _Res = with_avx::vec; _ArgTypes = {with_avx::vec}]’:
/usr/include/c /12/bits/std_function.h:587:7: note: the ABI for passing parameters with 32-byte alignment has changed in GCC 4.6
587 | operator()(_ArgTypes... __args) const
| ^~~~~~~~
Then if I run the code, sometimes segmentation fault is caused with the following output:
[1] 12710 segmentation fault ../build/unit_test
Sometimes, bad_function_call is thrown with the following output:
terminate called after throwing an instance of 'std::bad_function_call'
what(): bad_function_call
[1] 12678 IOT instruction ../build/unit_test
Both of these two errors are made when this line is executed:
vec ret = stdfunc(rand_vec);
I then used gdb for backtrace:
(gdb) bt
#0 0x00007ffff7e35521 in __cxa_throw () from /lib/x86_64-linux-gnu/libstdc .so.6
#1 0x00007ffff7e2c6f4 in std::__throw_bad_function_call() () from /lib/x86_64-linux-gnu/libstdc .so.6
#2 0x000055555555558b in std::function<with_avx::vec (with_avx::vec)>::operator()(with_avx::vec) const (this=0x7fffffffda74,
__args#0=...) at /usr/include/c /12/bits/std_function.h:590
#3 0x000055555555528d in main () at stdfunction_test.cpp:39
However if I don't add the flag, the code would run normally.
I think this is possibly caused by some kind of alignment problems like the warning sait I just don't know how to solve this.
My environment is listed on the following, hope they will be useful:
- g version:
g -12 (Ubuntu 12-20220319-1ubuntu1) 12.0.1 20220319 (experimental) [master r12-7719-g8ca61ad148f]
- OS: Ubuntu-22.04 running on WSL2
CodePudding user response:
Changing the target architecture half way through the file is causing your issue. Presumably parts of std::function
's implementation changes with the target architecture. Moving your pragma to the start of the file fixes the problem: https://godbolt.org/z/WP5ah38WP
It'll be safer in general if you set your architecture target via the compiler command line (e.g. -mavx2
) which will ensure all your code is compiled with the same architectures: https://godbolt.org/z/z5j79c5eh