C++: Implement isUnreachableInCall#13603
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MathiasVP merged 6 commits intogithub:mainfrom Jun 30, 2023
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DCA looks good: performance looks unchanged, and it's removing a small amount of FPs in various queries. |
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Jun 30, 2023
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Two small comments, otherwise LGTM.
| | test.cpp:136:9:136:16 | PointerAdd: ... += ... | test.cpp:143:18:143:21 | asdf | test.cpp:138:13:138:15 | arr | This pointer arithmetic may have an off-by-2 error allowing it to overrun $@ at this $@. | test.cpp:142:10:142:13 | asdf | asdf | test.cpp:138:12:138:15 | Load: * ... | read | | ||
| | test.cpp:151:5:151:11 | PointerAdd: access to array | test.cpp:148:23:148:28 | buffer | test.cpp:151:5:151:11 | access to array | This pointer arithmetic may have an off-by-1 error allowing it to overrun $@ at this $@. | test.cpp:147:19:147:24 | buffer | buffer | test.cpp:151:5:151:15 | Store: ... = ... | write | | ||
| | test.cpp:162:5:162:10 | PointerAdd: access to array | test.cpp:159:25:159:29 | array | test.cpp:162:5:162:10 | access to array | This pointer arithmetic may have an off-by-1 error allowing it to overrun $@ at this $@. | test.cpp:158:10:158:14 | array | array | test.cpp:162:5:162:19 | Store: ... = ... | write | | ||
| | test.cpp:191:27:191:30 | PointerAdd: access to array | test.cpp:201:14:201:20 | buffer2 | test.cpp:191:27:191:30 | access to array | This pointer arithmetic may have an off-by-1 error allowing it to overrun $@ at this $@. | test.cpp:200:19:200:25 | buffer2 | buffer2 | test.cpp:191:27:191:30 | Load: access to array | read | |
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I think the test annotation needs to be updated too.
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There's still a FP on that line, so we can't really remove the annotation. The annotation in question is:
// GOOD [FALSE POSITIVE]: `call_use(buffer2, 2)` won't reach this point.and this PR manages to remove the FP when the call originates from this source:
unsigned char buffer2[2];
call_use(buffer2,2);but not from this source:
unsigned char buffer2[2];
call_call_use(buffer2,2);
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Oh, great, test confusion.
Co-authored-by: Jeroen Ketema <93738568+jketema@users.noreply.github.com>
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isUnreachableInCallmakes use of the already-existing call context computed in the dataflow library to rule out infeasible dataflow paths in a function body based on the passed arguments.IIRC, @aschackmull mentioned that the implementation of this feature inside the dataflow library isn't super efficient, so I'm marking this as a draft while we run DCA to estimate the cost of this vs. the benefits provided (I'm looking at you FPs in
cpp/constant-array-overflow!)