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Asked: 2026-05-13T15:18:12+00:00

I am not sure how to deal with floating point exceptions in either C

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I am not sure how to deal with floating point exceptions in either C or C++. From wiki, there are following types of floating point exceptions:

IEEE 754 specifies five arithmetic errors that are to be recorded in "sticky bits" (by default; note that trapping and other alternatives are optional and, if provided, non-default).  

* inexact, set if the rounded (and returned) value is different from the mathematically exact result of the operation.  
* underflow, set if the rounded value is tiny (as specified in IEEE 754) and inexact (or maybe limited to if it has denormalisation loss, as per the 1984 version of IEEE 754), returning a subnormal value (including the zeroes).  
* overflow, set if the absolute value of the rounded value is too large to be represented (an infinity or maximal finite value is returned, depending on which rounding is used).  
* divide-by-zero, set if the result is infinite given finite operands (returning an infinity, either +∞ or −∞).  
* invalid, set if a real-valued result cannot be returned (like for sqrt(−1), or 0/0), returning a quiet NaN.

Is it that when any type of above exceptions happens, the program will exit abnormally? Or the program will carry this error on without mentioning anything and therefore make the error hard to debug?

Is a compiler like gcc able to give warning for some obvious case?

What can I do during coding my program to notify where the error happens and what types it is when it happens, so that I can locate the error easily in my code? Please give solutions in both C and C++ case.

Thanks and regards!

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1 Answer

  1. Editorial Team

    On Linux you can use the GNU extension feenableexcept (hidden right at the bottom of that page) to turn on trapping on floating point exceptions – if you do this then you’ll receive the signal SIGFPE when an exception occurs which you can then catch in your debugger. Watch out though as sometimes the signal gets thrown on the floating point instruction after the one that’s actually causing the problem, giving misleading line information in the debugger!

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