CodeProver does not detect overflow for non-volatile global variables

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Benjamin Colle
Benjamin Colle 2018-1-3
评论： Benjamin Colle 2018-1-5
Hello,
In an attempt to check the following ticket https://ch.mathworks.com/matlabcentral/answers/374199-codeprover-does-not-detect-overflow-underflow-with-unsigned-variables, I have noticed that CodeProver does not detect potential overflow when manipulating global variables which are not volatile. If I add the volatile keyword, CodeProver does raise a warning.
int8_t a, b, c;
volatile int8_t d, e, f;
void test (void){
a = b-c; // No warning
d = e-f; // Warning raised
}
I have tried also by making some computation on these variables somewhere else in the code, but the result is the same.
Is this a confirmed behavior on your side?

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采纳的回答

Alexandre De Barros
Hello,
I cannot reproduce your results: I have overflows for both volatile and non-volatile variables.
Are b and c full-range in your results ?
Alex
  2 个评论
Benjamin Colle
Benjamin Colle 2018-1-4
Thanks for your answer.
Even without values assigned prior to this operation, I get the behaviour. But at first (with int16 variables), I tried with b = -32768 and c = 32767.
Benjamin Colle
Benjamin Colle 2018-1-5
After investigation, it has been understood and found that:
- Code Prover, when a main is available, initializes variables to 0
- The assignment of values to those variables was done after the call of the function dealing with those variables
Therefore, Code Prover considered 0-value variables, which indeed do not overflow.
Thanks!

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