[task #16114] Print warning where integer overflow happens

[Pedram Ashofteh Ardakani]

URL:
  <https://savannah.gnu.org/task/?16114>

                 Summary: Print warning where integer overflow happens
                 Project: GNU Astronomy Utilities
            Submitted by: pedram
            Submitted on: Tue 01 Feb 2022 10:31:18 AM UTC
         Should Start On: Tue 01 Feb 2022 12:00:00 AM UTC
   Should be Finished on: Tue 01 Feb 2022 12:00:00 AM UTC
                Category: Arithmetic
                Priority: 5 - Normal
              Item Group: Enhancement
                  Status: None
                 Privacy: Public
        Percent Complete: 0%
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
                  Effort: 0.00

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Details:

As explained in bug #61969 , arithmetic reads inputs and uses the smallest
numerical data type possible to compute more efficiently with the least amount
of memory. However, the user might not be aware of the *integer overflow* that
might happen when calculations result in values that need larger storage
types. For example:


$ astarithmetic 254 2 +
0


This happens because _254_ and _2_ are both of type _uint8_ that can store a
maximum value of 255, so instead of getting the expected result _256_, we'd
get _0_ as the result of an integer overflow. One way to work around this for
now is to use floating points in the inputs, for instance:


$ astarithmetic 254.0 2 +
256


Since this is happening silently, we need to at least print a warning to
notify the user of the circumstances. So this task is defined here as Mohammad
pointed out in bug #61969:

> C library's 'errno.h' has a special error code for such range overflows:
'ERANGE'. We should add a check for this error code within arithmetic and if
it happens, a warning should be printed that an overflow has happened (to
standard-error; so its even printed with '--quiet'!). 




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