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false positive due to ignoring nonwritten value #24067

Open 7934dd98-f961-4531-b5c2-8c9a7260d231 opened 9 years ago

7934dd98-f961-4531-b5c2-8c9a7260d231 commented 9 years ago
Bugzilla Link 23693
Version 3.4
OS Linux
Attachments Report

Extended Description

I have banged my head over this one for quite a while. I think it either is a false positive ... or the construct is too complex for static analysis.

Have a look at the attached report. Keep an eye on variable "expr->r->nodetype". Between points 2 and 7, it never is written. However, the analyzer assumes in step 3 that it's value is 'A' but in step 6 it assumes it has changed to not 'A'. The only place where it could potentially have been written is in line 2285, as part of the function call. And, indeed, if I comment out that line, the report goes away.

Note that evalStrArrayCmp() never writes the expr->r parameter. If I change the prototype to explicitely make expt->r const, the warning goes away. So it looks the static analyzer now unerstands that the value cannot change.

Question now: is this a bug or an inherant limit in static analysis?

7934dd98-f961-4531-b5c2-8c9a7260d231 commented 9 years ago

I should have mentioned that one should skip to line 2268 in the attached report, this is where my report begins.

7934dd98-f961-4531-b5c2-8c9a7260d231 commented 9 years ago

assigned to @tkremenek