I have library which I have compiled on Ubuntu 18.04 using the version of gcc which comes bundled in the build-essential package, gcc 7.5.0.
If I then try to compile an application on Ubuntu 20.04 and link against the that library I previous built using the default gcc version, gcc 9.3.0, then I get a bunch of errors such as undefined reference to __expf_finite. Note, I do compile my original library with -Ofast as I need to take advantage of all optimizations. According to this SO question, it suggests that math-finite.h is no longer supported by the libc update.
So as a possible solution, I tried compiling my library on Ubuntu 20.04 using gcc 9.3.0 to then see if I can link against that library using an application compiled with gcc 7.5.0 on Ubuntu 18.04 (basically the reverse of the first scenario).
However, when I do this, I get ABI compat errors with std::string:
./trueface_sdk/libtf.a(ocl.cpp.o): In function `cv::ocl::Kernel::set(int, cv::ocl::KernelArg const&)':
ocl.cpp:(.text._ZN2cv3ocl6Kernel3setEiRKNS0_9KernelArgE+0x375): undefined reference to `std::__cxx11::basic_stringstream<char, std::char_traits<char>, std::allocator<char> >::basic_stringstream()'
ocl.cpp:(.text._ZN2cv3ocl6Kernel3setEiRKNS0_9KernelArgE+0x49d): undefined reference to `std::__cxx11::basic_stringstream<char, std::char_traits<char>, std::allocator<char> >::basic_stringstream()'
../trueface_sdk/libtf.a(ocl.cpp.o): In function `oclCleanupCallback.cold':
ocl.cpp:(.text.unlikely.oclCleanupCallback+0x36): undefined reference to `std::__cxx11::basic_stringstream<char, std::char_traits<char>, std::allocator<char> >::basic_stringstream()'
ocl.cpp:(.text.unlikely.oclCleanupCallback+0xcf): undefined reference to `std::__cxx11::basic_stringstream<char, std::char_traits<char>, std::allocator<char> >::basic_stringstream()'
ocl.cpp:(.text.unlikely.oclCleanupCallback+0x184): undefined reference to `std::__cxx11::basic_stringstream<char, std::char_traits<char>, std::allocator<char> >::basic_stringstream()'
../trueface_sdk/libtf.a(ocl.cpp.o):ocl.cpp:(.text._ZN2cv3ocl6Device4ImplC2EPv[_ZN2cv3ocl6Device4ImplC5EPv]+0xb7b): more undefined references to `std::__cxx11::basic_stringstream<char, std::char_traits<char>, std::allocator<char> >::basic_stringstream()' follow
../trueface_sdk/libtf.a(sqlite3.c.o):(.data.rel+0xb0): undefined reference to `fcntl64'
I also get undefined reference to fcntl64.
So what is the solution? How can I compile a library that will be compatible with multiple version of gcc?
Based on the comments, it looks like it is not compatible because of the use of the -Ofast compiler optimization flag.