The reason is because they’re initialized in the order they’re declared in your class, not the order you initialize them in the constructor and it’s warning you that your constructor’s order won’t be used. This is to help prevent errors where the initialization of b depends on a or vice-versa. The reason for this ordering … Read more
Here is a solution simpler than Johannes Schaub – litb’s one. It requires C++11. #include <type_traits> template <typename T, typename = int> struct HasX : std::false_type { }; template <typename T> struct HasX <T, decltype((void) T::x, 0)> : std::true_type { }; Update: A quick example and the explanation on how this works. For these types: … Read more
Try running (just after the failure) dmesg. Do you see a line like this? Out of memory: Kill process 23747 (cc1plus) score 15 or sacrifice child Killed process 23747, UID 2243, (cc1plus) total-vm:214456kB, anon-rss:178936kB, file-rss:5908kB Most likely that is your problem. Running make -j 8 runs lots of process which use more memory. The problem … Read more
This looks to be an bug/feature/issue with g++ in all of the versions I can test it on. Running int main() { int(*){} Is it C++14 or any other language? } On godbolt.org for all versions of g++ with no compilation flags give the following assembly ouput. main: pushq %rbp movq %rsp, %rbp movl $0, … Read more
It looks like you are most of the way there already. Well done with your investigation. Let’s see if I can help clear up the ‘why’ behind it. Here’s what the linker is doing. When you link your executable (‘main’ above) it has some symbols (functions and other things) that are unresolved. It will look … Read more
This is not how std::make_pair is intended to be used; you are not supposed to explicitly specify the template arguments. The C++11 std::make_pair takes two arguments, of type T&& and U&&, where T and U are template type parameters. Effectively, it looks like this (ignoring the return type): template <typename T, typename U> [return type] … Read more
The command-line option -fmax-errors=N directs the compiler to give up after N errors. This option is present in GCC 4.6 and later. The command-line option -Wfatal-errors directs the compiler to give up after one error. This option is present in GCC 4.0 and later. In both cases, warnings do not count toward the limit unless … Read more
If g++ still gives error Try using: g++ file.c -lstdc++ Look at this post: What is __gxx_personality_v0 for? Make sure -lstdc++ is at the end of the command. If you place it at the beginning (i.e. before file.c), you still can get this same error.
You want to use a function, not an alias, as Roman mentioned. Something like this: function mybuild { g++ $args -lib1 -lib2 … } To try this out, here’s a simple example: PS> function docmd { cmd /c $args there } PS> docmd echo hello hello there PS> You might also want to put this … Read more
In C++11, non-static data members, static constexpr data members, and static const data members of integral or enumeration type may be initialized in the class declaration. e.g. struct X { int i=5; const float f=3.12f; static const int j=42; static constexpr float g=9.5f; }; In this case, the i member of all instances of class … Read more