There are 2 answers/questions:
1) Why is there code, that divides by 0 (fully intentional)
2) Why is it called in your case.
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AFAIK its from the old days.
GDB did not catch FCP exceptions. (It does nowadays, but only if there is sufficient debug info)
A division by zero, produces a Sig...., and gdb will always get this.
In case of an unhandled exception, the LCL will catch it for you, and then call this code.
So the answer is, that somewhere else, you got an unhandled exception.