an error when running command ./build.sh

[ADgai234]

Ubuntu 20.04 Noetic
Hello,the following is the error.Could you please help me?
[ 65%] Linking CXX executable ../Examples/Monocular/mono_euroc
/usr/bin/ld: ../lib/libORB_SLAM2.so: undefined reference to DBoW2::FORB::L' /usr/bin/ld: ../lib/libORB_SLAM2.so: undefined reference to DUtils::Random::RandomInt(int, int)'
/usr/bin/ld: ../lib/libORB_SLAM2.so: undefined reference to DUtils::Random::SeedRandOnce()' /usr/bin/ld: ../lib/libORB_SLAM2.so: undefined reference to DUtils::Random::SeedRandOnce(int)'
collect2: error: ld returned 1 exit status
make[2]: *** [CMakeFiles/mono_euroc.dir/build.make:121：../Examples/Monocular/mono_euroc] 错误 1
make[1]: *** [CMakeFiles/Makefile2:88：CMakeFiles/mono_euroc.dir/all] 错误 2
make: *** [Makefile:84：all] 错误 2

[alam121]

The same error came for me. One wayout is to delete the build folder and build again:
mkdir build
cd build
cmake ..
make

This worked for me after ./buid.sh gave error

[mgrallos]

my error while running build.sh is

-- Configuring incomplete, errors occurred!
See also "/home/mariah/trial_ws/src/ORB_SLAM2/build/CMakeFiles/CMakeOutput.log".
make: *** No targets specified and no makefile found. Stop.

[irsyadtc]

I tried both ./build.sh and @alam121 approaches but both resulted to this error:

/home/irsyad2/Pangolin/components/pango_core/include/sigslot/signal.hpp:109:79: error: ‘decay_t’ is not a member of ‘std’; did you mean ‘decay’?
  109 | _weak_ptr_compatible_v = detail::is_weak_ptr_compatible<std::decay_t<P>>::value;
         |                                                              ^~~~~~~
         |                                                              decay

I built Pangolin from stevenlovegrove's repository at my home directory, master branch. Help please?

[Ashwij3]

@irsyadtc Any updates on the issue? I am facing the same error.

[irsyadtc]

Yes, see #1015
Pangolin is currently using a higher version c++ compiler while ORB-SLAM2 uses the older version.
Try remove Pangolin and git clone -b v0.5 https://github.com/stevenlovegrove/Pangolin.git then cmake again