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  • #2095

suggest to supply lower-bound for constant_too_large_2147483647 to Simplify

ID0001008: This issue was created automatically from Mantis Issue 1008. Further discussion may take place here.


Id Project Category View Due Date Updated
ID0001008 Frama-C Plug-in > jessie public 2011-11-03 2011-11-16
Reporter Jochen Assigned To cmarche Resolution open
Priority normal Severity feature Reproducibility N/A
Platform - OS - OS Version -
Product Version Frama-C Nitrogen-20111001 Target Version - Fixed in Version -

Description :

Simplify's problems with proving bounds of int values are well-known. E.g. for the program «int ftest(short s){return s;}», Simplify can't prove the obvious fact that the value s fits into the int type range [-2147483648..2147483647]. A reason is that the range bounds had to be modeled by abstract constants in order to prevent Simplify from crashing. I suggest to add by default an axiom "2147450877 < constant_too_large_2147483647 < constant_too_large_2147483648", in order to provide the sharpest bound possible without crashing Simplify. (A bound "2147450878" already causes a crash.)

Without such an axiom, there is no information about the size of those constants at all!

With that axiom (line 11-14 in the attached file pgm.sx), Simplify proves the above type-fit obligation, and hopefully numerous similar obligations.

Attachments

  • pgm.sx
  • ftest.c
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