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C#: Remove PreSsa library #20994

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Merged
hvitved merged 1 commit into from
Dec 12, 2025
+95 −487
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C#: Remove PreSsa library #20994

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193 changes: 47 additions & 146 deletions csharp/ql/lib/semmle/code/csharp/controlflow/Guards.qll
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Original file line number Diff line number Diff line change
Expand Up @@ -842,6 +842,40 @@ module Internal {
e3 = any(NullCoalescingExpr nce | e1 = nce.getLeftOperand() and e2 = nce.getRightOperand())
}

predicate nullValueImplied(Expr e) {
nullValue(e)
or
exists(Expr e1 | nullValueImplied(e1) and nullValueImpliedUnary(e1, e))
or
exists(Expr e1, Expr e2 |
nullValueImplied(e1) and nullValueImplied(e2) and nullValueImpliedBinary(e1, e2, e)
)
or
e =
any(Ssa::Definition def |
forex(Ssa::Definition u | u = def.getAnUltimateDefinition() | nullDef(u))
).getARead()
}

private predicate nullDef(Ssa::ExplicitDefinition def) {
nullValueImplied(def.getADefinition().getSource())
}

predicate nonNullValueImplied(Expr e) {
nonNullValue(e)
or
exists(Expr e1 | nonNullValueImplied(e1) and nonNullValueImpliedUnary(e1, e))
or
e =
any(Ssa::Definition def |
forex(Ssa::Definition u | u = def.getAnUltimateDefinition() | nonNullDef(u))
).getARead()
}

private predicate nonNullDef(Ssa::ExplicitDefinition def) {
nonNullValueImplied(def.getADefinition().getSource())
}

/** A callable that always returns a non-`null` value. */
private class NonNullCallable extends Callable {
NonNullCallable() { this = any(SystemObjectClass c).getGetTypeMethod() }
Expand Down Expand Up @@ -936,154 +970,21 @@ module Internal {
e = any(BinaryArithmeticOperation bao | result = bao.getAnOperand())
}

// The predicates in this module should be evaluated in the same stage as the CFG
// construction stage. This is to avoid recomputation of pre-basic-blocks and
// pre-SSA predicates
private module PreCfg {
private import semmle.code.csharp.controlflow.internal.PreBasicBlocks as PreBasicBlocks
private import semmle.code.csharp.controlflow.internal.PreSsa

private predicate nullDef(PreSsa::Definition def) {
nullValueImplied(def.getDefinition().getSource())
}

private predicate nonNullDef(PreSsa::Definition def) {
nonNullValueImplied(def.getDefinition().getSource())
}

private predicate emptyDef(PreSsa::Definition def) {
emptyValue(def.getDefinition().getSource())
}

private predicate nonEmptyDef(PreSsa::Definition def) {
nonEmptyValue(def.getDefinition().getSource())
}

deprecated predicate isGuard(Expr e, GuardValue val) {
(
e.getType() instanceof BoolType and
not e instanceof BoolLiteral and
not e instanceof SwitchCaseExpr and
not e instanceof PatternExpr and
exists(val.asBooleanValue())
or
e instanceof DereferenceableExpr and
val.isNullness(_)
) and
not e = any(ExprStmt es).getExpr() and
not e = any(LocalVariableDeclStmt s).getAVariableDeclExpr()
}

cached
private module CachedWithCfg {
private import semmle.code.csharp.Caching

private predicate firstReadSameVarUniquePredecessor(
PreSsa::Definition def, AssignableRead read
) {
read = def.getAFirstRead() and
(
not PreSsa::adjacentReadPairSameVar(_, read)
or
read = unique(AssignableRead read0 | PreSsa::adjacentReadPairSameVar(read0, read))
)
}

cached
predicate nullValueImplied(Expr e) {
nullValue(e)
or
exists(Expr e1 | nullValueImplied(e1) and nullValueImpliedUnary(e1, e))
or
exists(Expr e1, Expr e2 |
nullValueImplied(e1) and nullValueImplied(e2) and nullValueImpliedBinary(e1, e2, e)
)
or
e =
any(PreSsa::Definition def |
forex(PreSsa::Definition u | u = def.getAnUltimateDefinition() | nullDef(u))
).getARead()
}

cached
predicate nonNullValueImplied(Expr e) {
nonNullValue(e)
or
exists(Expr e1 | nonNullValueImplied(e1) and nonNullValueImpliedUnary(e1, e))
or
e =
any(PreSsa::Definition def |
forex(PreSsa::Definition u | u = def.getAnUltimateDefinition() | nonNullDef(u))
).getARead()
}

private predicate adjacentReadPairSameVarUniquePredecessor(
AssignableRead read1, AssignableRead read2
) {
PreSsa::adjacentReadPairSameVar(read1, read2) and
(
read1 = read2 and
read1 = unique(AssignableRead other | PreSsa::adjacentReadPairSameVar(other, read2))
or
read1 =
unique(AssignableRead other |
PreSsa::adjacentReadPairSameVar(other, read2) and other != read2
)
)
}

cached
predicate emptyValue(Expr e) {
e.(ArrayCreation).getALengthArgument().getValue().toInt() = 0
or
e.(ArrayInitializer).hasNoElements()
or
exists(Expr mid | emptyValue(mid) |
mid = e.(AssignExpr).getRValue()
or
mid = e.(Cast).getExpr()
)
or
exists(PreSsa::Definition def | emptyDef(def) | firstReadSameVarUniquePredecessor(def, e))
or
exists(MethodCall mc |
mc.getTarget().getAnUltimateImplementee().getUnboundDeclaration() =
any(SystemCollectionsGenericICollectionInterface c).getClearMethod() and
adjacentReadPairSameVarUniquePredecessor(mc.getQualifier(), e)
)
}

cached
predicate nonEmptyValue(Expr e) {
forex(Expr length | length = e.(ArrayCreation).getALengthArgument() |
length.getValue().toInt() != 0
)
or
e.(ArrayInitializer).getNumberOfElements() > 0
or
exists(Expr mid | nonEmptyValue(mid) |
mid = e.(AssignExpr).getRValue()
or
mid = e.(Cast).getExpr()
)
or
exists(PreSsa::Definition def | nonEmptyDef(def) |
firstReadSameVarUniquePredecessor(def, e)
)
or
exists(MethodCall mc |
mc.getTarget().getAnUltimateImplementee().getUnboundDeclaration() =
any(SystemCollectionsGenericICollectionInterface c).getAddMethod() and
adjacentReadPairSameVarUniquePredecessor(mc.getQualifier(), e)
)
}
}

import CachedWithCfg
deprecated predicate isGuard(Expr e, GuardValue val) {
(
e.getType() instanceof BoolType and
not e instanceof BoolLiteral and
not e instanceof SwitchCaseExpr and
not e instanceof PatternExpr and
exists(val.asBooleanValue())
or
e instanceof DereferenceableExpr and
val.isNullness(_)
) and
not e = any(ExprStmt es).getExpr() and
not e = any(LocalVariableDeclStmt s).getAVariableDeclExpr()
}

import PreCfg

private predicate interestingDescendantCandidate(Expr e) {
guardControls(e, _, _)
or
Expand Down
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