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C++: Suppress pointless compare in template inst.

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It still runs on uninstantiated templates because its underlying
libraries do. It's not clear whether that leads to other false
positives, but that's independent of the change I'm making here.
This commit is contained in:
Jonas Jensen
2018-10-03 14:32:44 +02:00
parent 2eea359f79
commit 364c9a6961
3 changed files with 4 additions and 5 deletions
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4
cpp/ql/src/Likely Bugs/Arithmetic/PointlessComparison.ql
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@@ -22,13 +22,15 @@ import UnsignedGEZero
// #define PRINTMSG(val,msg) { if (val >= PRINTLEVEL) printf(msg); }
//
// So to reduce the number of false positives, we do not report a result if
// the comparison is in a macro expansion.
// the comparison is in a macro expansion. Similarly for template
// instantiations.
from
ComparisonOperation cmp, SmallSide ss,
float left, float right, boolean value,
string reason
where
not cmp.isInMacroExpansion() and
not cmp.isFromTemplateInstantiation(_) and
reachablePointlessComparison(cmp, left, right, value, ss) and
// a comparison between an enum and zero is always valid because whether

3
cpp/ql/test/query-tests/Likely Bugs/Arithmetic/PointlessComparison/PointlessComparison.expected
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@@ -32,7 +32,4 @@
| PointlessComparison.c:129:12:129:16 | ... > ... | Comparison is always false because a <= 3. |
| PointlessComparison.c:197:7:197:11 | ... < ... | Comparison is always false because x >= 0. |
| RegressionTests.cpp:57:7:57:22 | ... <= ... | Comparison is always true because * ... <= 4294967295. |
| Templates.cpp:3:10:3:24 | ... <= ... | Comparison is always true because param <= 32767. |
| Templates.cpp:9:10:9:24 | ... <= ... | Comparison is always true because local <= 32767. |
| Templates.cpp:9:10:9:24 | ... <= ... | Comparison is always true because local <= 32767. |
| Templates.cpp:9:10:9:24 | ... <= ... | Comparison is always true because local <= 32767. |

2
cpp/ql/test/query-tests/Likely Bugs/Arithmetic/PointlessComparison/Templates.cpp
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@@ -1,6 +1,6 @@
template<typename T>
bool sometimesPointless(T param) {
return param <= 0xFFFF; // GOOD (FALSE POSITIVE: hypothetical instantiations are okay)
return param <= 0xFFFF; // GOOD (hypothetical instantiations are okay)
}
template<typename T>