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from the README-gcc-tdm.text file --

"GCC currently supports two methods of stack frame unwinding: Dwarf-2 (DW2) or SJLJ (setjmp/longjmp). Until recently, only SJLJ has been available for the Windows platform. This affects you, the end user, primarily in programs that throw and catch exceptions. Programs which utilize the DW2 unwind method generally execute more quickly than programs which utilize the SJLJ method, because the DW2 method incurs no runtime overhead until an exception is thrown. However, the DW2 method does incur a size penalty on code that must handle exceptions, and more importantly the DW2 method cannot yet unwind (pass exceptions) through "foreign" stack frames: stack frames compiled by another non-DW2-enabled compiler, such as OS DLLs in a Windows callback.

This means that you should in general choose the SJLJ version of the TDM-GCC builds unless you know you need faster exception-aware programs and can be certain you will never throw an exception through a foreign stack area.

As distributed, the SJLJ and DW2 packages of TDM-GCC can coexist peacefully extracted to the same directory (i.e. any files in common are for all intents and purposes identical), because the driver executables (the ones in the "bin" directory) are suffixed with "-dw2" for the DW2 build, and the libraries and other executables hide in another "-dw2" directory in "lib(exec)/gcc/mingw32". This allows you to use the same single addition to your PATH, and use DW2 exceptions only when you need them by calling "gcc-dw2", etc. If you truly want DW2 exceptions as the default when calling "gcc" (from Makefiles or configury systems, for example), you can rename or copy the suffixed executables to their original names."

libstdc++-6.dll will export either __gxx_personality_v0 or __gxx_personality_sj0 depending on which unwinding method it supports. opencv uses Dwarf-2. If you use tdm-gcc (http://tdm-gcc.tdragon.net/) you can choose which unwinding method you want.