josyoun
commented
8 years ago Quick question: Are you compiling develop or master? Short answer is that I believe this has been fixed on develop and I can port that to master. Long answer, this arises from a bug with alias templates in GCC that was resolved between GCC 4.8 and GCC 4.9 and above. Consider the program:
#include <iostream>
#include <typeinfo>
#include <cstdlib>
template <typename U,template <typename> class T>
struct foo{
static void print() {
std::cerr << "Undefined for type: "<< typeid(T <U>).name()
<< std::endl;
exit(EXIT_FAILURE);
}
};
// Create a dummy templated class
template <typename T>
struct bar {};
// Create a template alias based on this class
template <typename T> using bar_alias = bar <T>;
template <typename T>
struct foo <T,bar> {
static void print() {
std::cout << "This is bar" << std::endl;
}
};
int main() {
foo <double,bar>::print();
foo <double,bar_alias>::print();
}In GCC 4.9, this produces:
$ ./alias_template
This is bar
This is barIn GCC 4.8 this produces:
$ ./alias_template
This is bar
Undefined for type: 3barIdEAnyway, the result from GCC 4.9 and later is the correct result. Prior to my use of newer versions of GCC, I didn't know this was the case and I used an old work around that was incorrect, which I'm pretty sure is what the error above is. Technically, that code I attached is something slightly different, but I believe it to be a manifestation of the same bug.
I do have a fix and I can back port it into master. That being said, my preference would be to just fix up a couple of existing documentation issues and then do a new release, which would also fix things. In the immediate future:
- You can compile without unit tests and it should work
- Please verify this is on master and not develop
By the way, develop is now using C++14, so your CMake options will need to change slightly. In terms of when there's a new release, I do intend to do so soon. I could probably do that this week.
Dapid
I am getting the following errors when compiling. I am using release mode, and I have manually included the
--std=c++11flag. The OS is Fedora 22, GCC 5.1.1, (c)cmake 3.3.2: