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Fix translation of __builtin_*_overflow functions #684
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maul-esel
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Oct 10, 2024
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Thanks for noticing and fixing this! I left some minor comments and questions, but overall 👍
...ltimate/cdt/translation/implementation/base/expressiontranslation/ExpressionTranslation.java
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...k/ultimate/cdt/translation/implementation/base/expressiontranslation/IntegerTranslation.java
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.../ultimate/cdt/translation/implementation/base/standardfunctions/StandardFunctionHandler.java
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…initePrecisionExpression (and show example for conversion and why this is in the range)
This reverts commit f2fe42e.
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In GNU C there are functions to check for overflows of arithmetic operations (
__builtin_*_overflow
). These functions perform an arithmetic operation on the first two arguments (without producing any overflows), write the result to the third argument and return whether an overflow would occur using the normal arithmetic operation.Currently, we simply overapproximate the return value of these functions. This is in general unsound as we do not consider that the third argument changes at all. Also this is quite imprecise, which led to 55
unknown
results in SV-COMP 24.Therefore this PR handles these functions properly. This is done in the following way:
&x
. Therefore this depends on Fix translation of atomic functions #685).For each of the three cases I added a new method to
ExpressionTranslation
accordingly, as these cases differ between the integer translation and the bitvector translation.