gcc4.8

I have a problem using Apache Portable Runtime on Ubuntu with GCC 4.8.1 The problem is that the off64_t from <sys/types.h> is not available when compiling with gcc . (When compiling with g++ everything work fine) Does anybody know which compiler switch to use to enable off64_t ? (I know that defining _LARGEFILE_SOURCE _LARGEFILE64_SOURCE avoids the problem, but wondering if this is the right way) To reproduce the error one can simply try to compile the following code: #include <sys/types.h> off64_t a_variable; off64_t is not a language defined type. No compiler switch will make it available.

In C, I have a task where I must do multiplication, inversion, trasposition, addition etc. etc. with huge matrices allocated as 2-dimensional arrays, (arrays of arrays). I have found the gcc flag -funroll-all-loops . If I understand correctly, this will unroll all loops automatically without any efforts by the programmer. My questions: a) Does gcc include this kind of optimization with the various optimization flags as -O1 , -O2 etc.? b) Do I have to use any pragma s inside my code to take advantage of loop unrolling or are loops identified automatically? c) Why is this option not enabled by

I experienced crashes running an old code of mine on a system which doesn't support SSE4.1, I debugged a bit and found SSE instructions in the glibc, is that possible? Why isn't this reported in gcc 4.8.1 release notes? You can see what optimizations are used by GCC with the following command: $ gcc -Q --help=target For instance, on my machine, GCC does not enable sse4.1 by default: $ gcc -Q --help=target | grep msse4.1 -msse4.1 [disabled] However, it is supported because it appears in /proc/cpuinfo . And indeed, if I ask GCC to optimize the generated code for my machine, it enables sse4.1: $

I am trying to get some (hitherto) windows code to compile on a unix machine but am getting some errors at the following method: namespace EDIN { void World::Save(char const filename[]) { std::ofstream ofs(filename); boost::archive::text_oarchive oa(ofs); oa << this << cellSequence << report; // line 590: error! } } The error looks like this: test.cpp: In member function ‘void EDIN::World::Save(const char*)’: test.cpp:122:12: error: no match for ‘operator<<’ (operand types are ‘boost::archive::text_oarchive’ and ‘EDIN::World*’) oa << this << cellSequence << report; // line 590: error! ^ test

I'm trying to create a object that can be given a function and its parameters to his constructor. This class will then call the given function inside a lambda that is instead passed to a thread. Something along the lines of class worker { public: template <class Fn, class... Args> explicit worker(Fn f, Args ... args) { t = std::thread([&]() -> void { f(args...); }); } private: std::thread t; }; int main() { worker t([]() -> void { for (size_t i = 0; i < 100; i++) std::cout << i << std::endl; }); return 0; } But I get the following error error: parameter packs not expanded with '...': f(args...

The GCC compiler $ gcc --version gcc (GCC) 4.8.2 ... doesn't generate an inc assembly instruction, where it could actually be useful, like in this C program: int main(int argc, char **argv) { int sum = 0; int i; for(i = 0; i < 1000000000L; i++) <---- that "i++" sum += i; return sum; } Instead, it generates an add instruction: 0000000000000000 <main>: 0: 31 d2 xor %edx,%edx 2: 31 c0 xor %eax,%eax 4: 0f 1f 40 00 nopl 0x0(%rax) 8: 01 d0 add %edx,%eax a: 83 c2 01 add $0x1,%edx <---- HERE d: 81 fa 00 ca 9a 3b cmp $0x3b9aca00,%edx 13: 75 f3 jne 8 <main+0x8> 15: f3 c3 repz retq Why does it do this?