C++: Fix false positive in 'cpp/cpp/comparison-of-identical-expressions'.

MathiasVP · MathiasVP · commit b2082cc3da99 · 2021-12-14T16:39:25.000Z
diff --git a/cpp/ql/src/Likely Bugs/Arithmetic/PointlessSelfComparison.qll b/cpp/ql/src/Likely Bugs/Arithmetic/PointlessSelfComparison.qll
@@ -29,7 +29,9 @@ predicate pointlessSelfComparison(ComparisonOperation cmp) {
     not exists(lhs.getQualifier()) and // Avoid structure fields
     not exists(rhs.getQualifier()) and // Avoid structure fields
     not convertedExprMightOverflow(lhs) and
-    not convertedExprMightOverflow(rhs)
+    not convertedExprMightOverflow(rhs) and
+    // Don't warn if the comparison is part of a template argument.
+    not any(ClassTemplateInstantiation inst).getATemplateArgument() = cmp.getParent*()
   )
 }
 
diff --git a/cpp/ql/test/query-tests/Likely Bugs/Arithmetic/BadAdditionOverflowCheck/PointlessSelfComparison.expected b/cpp/ql/test/query-tests/Likely Bugs/Arithmetic/BadAdditionOverflowCheck/PointlessSelfComparison.expected
@@ -1,5 +1,4 @@
 | templates.cpp:17:5:17:25 | ... < ... | Self comparison. |
-| templates.cpp:31:20:31:41 | ... <= ... | Self comparison. |
 | test.cpp:13:11:13:21 | ... == ... | Self comparison. |
 | test.cpp:79:11:79:32 | ... == ... | Self comparison. |
 | test.cpp:83:10:83:15 | ... == ... | Self comparison. |

Original file line number	Diff line number	Diff line change
`@@ -29,7 +29,9 @@ predicate pointlessSelfComparison(ComparisonOperation cmp) {`
`29`	`29`	`not exists(lhs.getQualifier()) and // Avoid structure fields`
`30`	`30`	`not exists(rhs.getQualifier()) and // Avoid structure fields`
`31`	`31`	`not convertedExprMightOverflow(lhs) and`
`32`		`- not convertedExprMightOverflow(rhs)`
	`32`	`+ not convertedExprMightOverflow(rhs) and`
	`33`	`+ // Don't warn if the comparison is part of a template argument.`
	`34`	`+ not any(ClassTemplateInstantiation inst).getATemplateArgument() = cmp.getParent*()`
`33`	`35`	`)`
`34`	`36`	`}`
`35`	`37`
Original file line number	Diff line number	Diff line change
`@@ -1,5 +1,4 @@`
`1`	`1`	`\| templates.cpp:17:5:17:25 \| ... < ... \| Self comparison. \|`
`2`		`-\| templates.cpp:31:20:31:41 \| ... <= ... \| Self comparison. \|`
`3`	`2`	`\| test.cpp:13:11:13:21 \| ... == ... \| Self comparison. \|`
`4`	`3`	`\| test.cpp:79:11:79:32 \| ... == ... \| Self comparison. \|`
`5`	`4`	`\| test.cpp:83:10:83:15 \| ... == ... \| Self comparison. \|`