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Rust: Prune CFG for impossible true/false edges

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This commit is contained in:
Tom Hvitved
2024-09-27 13:27:49 +02:00
parent bf58bdd2bd
commit dc4160b24a
2 changed files with 18 additions and 7 deletions
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20
rust/ql/lib/codeql/rust/controlflow/internal/Completion.qll
View File

@@ -67,6 +67,13 @@ abstract class ConditionalCompletion extends NormalCompletion {
abstract ConditionalCompletion getDual();
}
/** Holds if node `n` has the Boolean constant value `value`. */
private predicate isBooleanConstant(AstNode n, Boolean value) {
n.(LiteralExpr).getTextValue() = value.toString()
or
isBooleanConstant(n.(ParenExpr).getExpr(), value)
}
/**
* A completion that represents evaluation of an expression
* with a Boolean value.
@@ -74,7 +81,7 @@ abstract class ConditionalCompletion extends NormalCompletion {
class BooleanCompletion extends ConditionalCompletion, TBooleanCompletion {
BooleanCompletion() { this = TBooleanCompletion(value) }
override predicate isValidForSpecific(AstNode e) {
private predicate isValidForSpecific0(AstNode e) {
e = any(IfExpr c).getCondition()
or
any(MatchArm arm).getGuard() = e
@@ -84,7 +91,7 @@ class BooleanCompletion extends ConditionalCompletion, TBooleanCompletion {
e = expr.getLhs()
)
or
exists(Expr parent | this.isValidForSpecific(parent) |
exists(Expr parent | this.isValidForSpecific0(parent) |
parent =
any(PrefixExpr expr |
expr.getOperatorName() = "!" and
@@ -103,6 +110,15 @@ class BooleanCompletion extends ConditionalCompletion, TBooleanCompletion {
)
}
override predicate isValidForSpecific(AstNode e) {
this.isValidForSpecific0(e) and
(
isBooleanConstant(e, value)
or
not isBooleanConstant(e, _)
)
}
/** Gets the dual Boolean completion. */
override BooleanCompletion getDual() { result = TBooleanCompletion(value.booleanNot()) }

5
rust/ql/test/library-tests/controlflow/Cfg.expected
View File

@@ -262,13 +262,8 @@
| test.rs:146:1:151:1 | enter dead_code | test.rs:147:5:149:5 | ExprStmt | |
| test.rs:146:1:151:1 | exit dead_code (normal) | test.rs:146:1:151:1 | exit dead_code | |
| test.rs:147:5:149:5 | ExprStmt | test.rs:147:9:147:12 | true | |
| test.rs:147:5:149:5 | IfExpr | test.rs:150:5:150:13 | ExprStmt | |
| test.rs:147:8:147:13 | ParenExpr | test.rs:147:5:149:5 | IfExpr | false |
| test.rs:147:8:147:13 | ParenExpr | test.rs:148:9:148:17 | ExprStmt | true |
| test.rs:147:9:147:12 | true | test.rs:147:8:147:13 | ParenExpr | |
| test.rs:148:9:148:16 | ReturnExpr | test.rs:146:1:151:1 | exit dead_code (normal) | return |
| test.rs:148:9:148:17 | ExprStmt | test.rs:148:16:148:16 | 0 | |
| test.rs:148:16:148:16 | 0 | test.rs:148:9:148:16 | ReturnExpr | |
| test.rs:150:5:150:12 | ReturnExpr | test.rs:146:1:151:1 | exit dead_code (normal) | return |
| test.rs:150:5:150:13 | ExprStmt | test.rs:150:12:150:12 | 1 | |
| test.rs:150:12:150:12 | 1 | test.rs:150:5:150:12 | ReturnExpr | |