Stop Implicit Type Conversion in Coder
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Hello All
As per ISO 26262, for ASIL B to ASIL D, there must not be an implicit data type conversion. But in MATLAB, we can have
testValue = uint8(2);
testValue = -126; % It is perfectly fine but shall throw a warning or error
Is there anyway to throw a compile time warning here? Suggestions are welcome.
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Thomas Blazek
2018-3-8
So, MATLAB is dynamically typed. That means, by assignment, you overwrite the type. It is not a type conversion, it is literally setting a new type. And, MATLAB is very liberal about it. Furthermore, it is interpreted, not compiled, therefore no compile-time checks are possible.
That said, there is a workaround if you really want to be sure. You can Define the following Class
classdef Uint8Class
properties
value = []
end
methods
function obj = set.value(obj,in)
if in >= 0 && in < 256
obj.value = in;
else
error('Not a Uint8')
end
end
function out = get.value(obj)
out = uint8(obj.value);
end
end
end
x = Uint8Class;
x.value = 3; % works
display(x.value)
x.value = -2 % Raises an error
The way this works is that it overrides get and set methods of "x". Then, you can write your own checks on assignment. The downside is that you have to address the value by "variable.value" instead of just "variable", but it does allow for checks as you want them, and even "fails in a meaningful way".
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Thomas Blazek
2018-3-8
Ah ok, sorry I didn't quite catch that, in that case I do not have an idea, Sorry.
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