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C++ IO Functions not working

  • Hello,

    the standard io functions of c++, do not seem to be working, while the C ones are working.

    Minimum example, gives segmentation fault. Obviously you should not use printf in c++, but std::cout is also not working.

    #include <signal.h>
    #include <fstream>
    #include <iostream>
    using namespace std;
    bool shutdown_ = false;
    void sigint_handler(int s)
            shutdown_ = true;
    int main(const int argc, const char **argv) {
            signal(SIGINT, sigint_handler);
            printf("hello printf\n");
            ofstream outFile ("test.txt");
            outFile << "hello" << std::endl;
            return 0;


    root@Omega-229D:~# ./main
    hello printf
    Segmentation fault

    So it is compiling, but not working then when running the program.

  • @joh :

    Just curious..
    Are you cross compiling it using "toolchain-mipsel_24kc_gcc-7.3.0_musl" ? Also, would like to know the options passed ..

    I use mipsel-linux-muslsf-native.tgz, which is 32-bit, from http://musl.cc (v 9.3.1) for compiling..
    Runtime is musl-libc 1.2.1 from http://musl.libc.org, compiled in qemu, then moved to omega2.

    The setup is running under qemu-mipsel in Linux x64.Malta 24kec processor can take only 256MB ram.I guess it is by mips design, and no smp.

    To complie my 2k loc, that is good.

    I have compiled protobuf3 under qemu.

    When compiling the entire Omega/OpenWRT..things are different, though.We need lot of ram, smp..

    Just sharing.


  • @joh I compiled your sample and ran it on my device without issue. I would add a statement to your sig handler to determine what signal you may be capturing which I suspect is where you will identify the root cause.

    void sigint_handler(int s) {
    printf("Caught signal %s", s);
    shutdown_ = true;

  • Ok I figured out now that the basic example (https://github.com/OnionIoT/c-cross-compile-example) is working with the file operations.

    @tjoseph1 Yes I am using the basic "toolchain-mipsel_24kc_gcc-7.3.0_musl" with the Flags from the xCompile file.

    @crispyoz The signal handler did not show anything, I don't think it's the problem.

    I have a lot of libraries included, which seem to cause the problem, now I have to find out which one is causing it.

    But I still wonder why the library would change the behavior of the file io functions..

  • Ok I figured out now that the uClibc++ is the problem, I require this library for zmq.

    I am using the uClibc++ and zmq just from the make menuconfig, so seems I need to find another version here...

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