It is a problem that appeared when I first updated to macOS Sierra yesterday.
GDB itself is running OK. However, somehow, it cannot run my program. When I type \'run
I got the same error after updating to macOS Sierra. Temporarily I changed debugger to LLDB using the library lldbmi2:
1. git clone https://github.com/freedib/lldbmi2.git lldbmi2
2. cd lldbmi2
3. mkdir build
4. cd build
5. cmake ../
6. make
7. sudo make install
Once lldbmi2 is installed, you can debug your application by creating a new C/C++ Application in Debug Configurations... and change the GDB debugger (in Debugger tab) from gdb to lldbmi2. Options to lldbmi2 may be set there. Something like /usr/local/bin/lldbmi2 --log.
Everything seems to be working fine, and even better as GDB.