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Oct 24, 2025
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C#: Delete exception splitting. #20677

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dff327e
C#: Delete exception splitting.
aschackmull Oct 23, 2025
ebb50cd
C#: Accept qltest changes.
aschackmull Oct 23, 2025
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2 changes: 0 additions & 2 deletions csharp/ql/lib/semmle/code/csharp/controlflow/ControlFlowGraph.qll
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Original file line number Diff line number Diff line change
Expand Up @@ -294,8 +294,6 @@ module ControlFlow {
}

class Split = Splitting::Split;

class ExceptionHandlerSplit = Splitting::ExceptionHandlerSplitting::ExceptionHandlerSplit;
}

class BasicBlock = BBs::BasicBlock;
Expand Down
182 changes: 2 additions & 180 deletions csharp/ql/lib/semmle/code/csharp/controlflow/internal/Splitting.qll
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Expand Up @@ -25,8 +25,7 @@ private module Cached {
newtype TSplitKind =
TInitializerSplitKind() or
TConditionalCompletionSplitKind() or
TAssertionSplitKind() or
TExceptionHandlerSplitKind()
TAssertionSplitKind()

cached
newtype TSplit =
Expand All @@ -35,8 +34,7 @@ private module Cached {
TAssertionSplit(AssertionSplitting::Assertion a, int i, boolean success) {
exists(a.getExpr(i)) and
success in [false, true]
} or
TExceptionHandlerSplit(ExceptionClass ec)
}
}

import Cached
Expand Down Expand Up @@ -449,179 +447,3 @@ module AssertionSplitting {
}
}
}

module ExceptionHandlerSplitting {
private newtype TMatch =
TAlways() or
TMaybe() or
TNever()

/**
* A split for elements belonging to a `catch` clause, which determines the type of
* exception to handle. For example, in
*
* ```csharp
* try
* {
* if (M() > 0)
* throw new ArgumentException();
* else if (M() < 0)
* throw new ArithmeticException("negative");
* else
* return;
* }
* catch (ArgumentException e)
* {
* Log.Write("M() positive");
* }
* catch (ArithmeticException e) when (e.Message != null)
* {
* Log.Write($"M() {e.Message}");
* }
* ```
*
* all control flow nodes in
* ```csharp
* catch (ArgumentException e)
* ```
* and
* ```csharp
* catch (ArithmeticException e) when (e.Message != null)
* ```
* have two splits: one representing the `try` block throwing an `ArgumentException`,
* and one representing the `try` block throwing an `ArithmeticException`.
*/
class ExceptionHandlerSplit extends Split, TExceptionHandlerSplit {
private ExceptionClass ec;

ExceptionHandlerSplit() { this = TExceptionHandlerSplit(ec) }

/** Gets the exception type that this split represents. */
ExceptionClass getExceptionClass() { result = ec }

override string toString() { result = "exception: " + ec.toString() }
}

private class ExceptionHandlerSplitKind extends SplitKind, TExceptionHandlerSplitKind {
override int getListOrder() { result = AssertionSplitting::getNextListOrder() }

override string toString() { result = "ExceptionHandler" }
}

int getNextListOrder() { result = AssertionSplitting::getNextListOrder() + 1 }

private class ExceptionHandlerSplitImpl extends SplitImpl instanceof ExceptionHandlerSplit {
override ExceptionHandlerSplitKind getKind() { any() }

override predicate hasEntry(AstNode pred, AstNode succ, Completion c) {
// Entry into first catch clause
exists(Statements::TryStmtTree ts |
super.getExceptionClass() = ts.getAThrownException(pred, c)
|
succ(pred, succ, c) and
succ = ts.(TryStmt).getCatchClause(0).(SpecificCatchClause)
)
}

override predicate hasEntryScope(CfgScope scope, AstNode first) { none() }

/**
* Holds if this split applies to catch clause `scc`. The parameter `match`
* indicates whether the catch clause `scc` may match the exception type of
* this split.
*/
private predicate appliesToCatchClause(SpecificCatchClause scc, TMatch match) {
exists(Statements::TryStmtTree ts, ExceptionClass ec |
ec = super.getExceptionClass() and
ec = ts.getAThrownException(_, _) and
scc = ts.(TryStmt).getACatchClause()
|
if scc.getCaughtExceptionType() = ec.getABaseType*()
then match = TAlways()
else
if scc.getCaughtExceptionType() = ec.getASubType+()
then match = TMaybe()
else match = TNever()
)
}

/**
* Holds if this split applies to control flow element `pred`, where `pred`
* is a valid predecessor with completion `c`.
*/
private predicate appliesToPredecessor(AstNode pred, Completion c) {
this.appliesTo(pred) and
(succ(pred, _, c) or scopeLast(_, pred, c)) and
(
pred instanceof SpecificCatchClause
implies
pred =
any(SpecificCatchClause scc |
if c instanceof MatchingCompletion
then
exists(TMatch match | this.appliesToCatchClause(scc, match) |
c =
any(MatchingCompletion mc |
if mc.isMatch() then match != TNever() else match != TAlways()
)
)
else (
(scc.isLast() and c instanceof ThrowCompletion)
implies
exists(TMatch match | this.appliesToCatchClause(scc, match) | match != TAlways())
)
)
)
}

/**
* Holds if this split applies to `pred`, and `pred` may exit this split
* with throw completion `c`, because it belongs to the last `catch` clause
* in a `try` statement.
*/
private predicate hasLastExit(AstNode pred, ThrowCompletion c) {
this.appliesToPredecessor(pred, c) and
exists(TryStmt ts, SpecificCatchClause scc, int last |
last(ts.getCatchClause(last), pred, c)
|
ts.getCatchClause(last) = scc and
scc.isLast() and
c.getExceptionClass() = super.getExceptionClass()
)
}

override predicate hasExit(AstNode pred, AstNode succ, Completion c) {
this.appliesToPredecessor(pred, c) and
succ(pred, succ, c) and
(
// Exit out to `catch` clause block
first(any(SpecificCatchClause scc).getBlock(), succ)
or
// Exit out to a general `catch` clause
succ instanceof GeneralCatchClause
or
// Exit out from last `catch` clause (no catch clauses match)
this.hasLastExit(pred, c)
)
}

override predicate hasExitScope(CfgScope scope, AstNode last, Completion c) {
// Exit out from last `catch` clause (no catch clauses match)
this.hasLastExit(last, c) and
scopeLast(scope, last, c)
}

override predicate hasSuccessor(AstNode pred, AstNode succ, Completion c) {
this.appliesToPredecessor(pred, c) and
this.appliesSucc(pred, succ, c) and
not first(any(SpecificCatchClause scc).getBlock(), succ) and
not succ instanceof GeneralCatchClause and
not exists(TryStmt ts, SpecificCatchClause scc, int last |
last(ts.getCatchClause(last), pred, c)
|
ts.getCatchClause(last) = scc and
scc.isLast()
)
}
}
}
2 changes: 1 addition & 1 deletion csharp/ql/test/library-tests/assignables/AssignableDefinitionNode.expected
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Original file line number Diff line number Diff line change
Expand Up @@ -31,7 +31,7 @@
| Assignables.cs:69:13:69:17 | ... = ... | Assignables.cs:69:13:69:17 | ... = ... |
| Assignables.cs:78:22:78:22 | String s | Assignables.cs:78:22:78:22 | String s |
| Assignables.cs:82:21:82:33 | String temp = ... | Assignables.cs:82:21:82:33 | String temp = ... |
| Assignables.cs:84:30:84:30 | Exception e | Assignables.cs:84:30:84:30 | [exception: OutOfMemoryException] Exception e |
| Assignables.cs:84:30:84:30 | Exception e | Assignables.cs:84:30:84:30 | Exception e |
| Assignables.cs:92:9:92:54 | ... = ... | Assignables.cs:92:9:92:54 | ... = ... |
| Assignables.cs:92:9:92:54 | ... = ... | Assignables.cs:92:9:92:54 | ... = ... |
| Assignables.cs:92:9:92:54 | ... = ... | Assignables.cs:92:9:92:54 | ... = ... |
Expand Down
38 changes: 17 additions & 21 deletions csharp/ql/test/library-tests/controlflow/graph/BasicBlock.expected
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Original file line number Diff line number Diff line change
Expand Up @@ -367,12 +367,10 @@
| ExitMethods.cs:20:10:20:11 | enter M3 | ExitMethods.cs:20:10:20:11 | exit M3 | 7 |
| ExitMethods.cs:26:10:26:11 | enter M4 | ExitMethods.cs:26:10:26:11 | exit M4 | 7 |
| ExitMethods.cs:32:10:32:11 | enter M5 | ExitMethods.cs:32:10:32:11 | exit M5 | 7 |
| ExitMethods.cs:38:10:38:11 | enter M6 | ExitMethods.cs:42:13:42:30 | call to method ErrorAlways | 7 |
| ExitMethods.cs:38:10:38:11 | enter M6 | ExitMethods.cs:44:9:47:9 | catch (...) {...} | 8 |
| ExitMethods.cs:38:10:38:11 | exit M6 (normal) | ExitMethods.cs:38:10:38:11 | exit M6 | 2 |
| ExitMethods.cs:44:9:47:9 | [exception: ArgumentException] catch (...) {...} | ExitMethods.cs:44:9:47:9 | [exception: ArgumentException] catch (...) {...} | 1 |
| ExitMethods.cs:44:9:47:9 | [exception: Exception] catch (...) {...} | ExitMethods.cs:44:9:47:9 | [exception: Exception] catch (...) {...} | 1 |
| ExitMethods.cs:45:9:47:9 | {...} | ExitMethods.cs:46:13:46:19 | return ...; | 2 |
| ExitMethods.cs:48:9:51:9 | [exception: Exception] catch (...) {...} | ExitMethods.cs:48:9:51:9 | [exception: Exception] catch (...) {...} | 1 |
| ExitMethods.cs:48:9:51:9 | catch (...) {...} | ExitMethods.cs:48:9:51:9 | catch (...) {...} | 1 |
| ExitMethods.cs:49:9:51:9 | {...} | ExitMethods.cs:50:13:50:19 | return ...; | 2 |
| ExitMethods.cs:54:10:54:11 | enter M7 | ExitMethods.cs:54:10:54:11 | exit M7 | 6 |
| ExitMethods.cs:60:10:60:11 | enter M8 | ExitMethods.cs:60:10:60:11 | exit M8 | 6 |
Expand Down Expand Up @@ -424,25 +422,26 @@
| Finally.cs:19:10:19:11 | exit M2 (abnormal) | Finally.cs:19:10:19:11 | exit M2 (abnormal) | 1 |
| Finally.cs:19:10:19:11 | exit M2 (normal) | Finally.cs:19:10:19:11 | exit M2 (normal) | 1 |
| Finally.cs:24:13:24:19 | return ...; | Finally.cs:24:13:24:19 | return ...; | 1 |
| Finally.cs:26:9:29:9 | [exception: Exception] catch (...) {...} | Finally.cs:26:9:29:9 | [exception: Exception] catch (...) {...} | 1 |
| Finally.cs:26:38:26:39 | [exception: Exception] IOException ex | Finally.cs:26:48:26:51 | [exception: Exception] true | 2 |
| Finally.cs:26:9:29:9 | catch (...) {...} | Finally.cs:26:9:29:9 | catch (...) {...} | 1 |
| Finally.cs:26:38:26:39 | IOException ex | Finally.cs:26:48:26:51 | true | 2 |
| Finally.cs:27:9:29:9 | {...} | Finally.cs:28:13:28:18 | throw ...; | 2 |
| Finally.cs:30:9:40:9 | [exception: Exception] catch (...) {...} | Finally.cs:30:9:40:9 | [exception: Exception] catch (...) {...} | 1 |
| Finally.cs:30:41:30:42 | [exception: Exception] ArgumentException ex | Finally.cs:34:21:34:24 | true | 6 |
| Finally.cs:30:9:40:9 | catch (...) {...} | Finally.cs:30:9:40:9 | catch (...) {...} | 1 |
| Finally.cs:30:41:30:42 | ArgumentException ex | Finally.cs:34:21:34:24 | true | 6 |
| Finally.cs:34:27:34:32 | throw ...; | Finally.cs:38:17:38:44 | throw ...; | 5 |
| Finally.cs:41:9:43:9 | [exception: Exception] catch (...) {...} | Finally.cs:41:9:43:9 | [exception: Exception] catch (...) {...} | 1 |
| Finally.cs:41:9:43:9 | catch (...) {...} | Finally.cs:41:9:43:9 | catch (...) {...} | 1 |
| Finally.cs:42:9:43:9 | {...} | Finally.cs:42:9:43:9 | {...} | 1 |
| Finally.cs:44:9:47:9 | catch {...} | Finally.cs:46:13:46:19 | return ...; | 3 |
| Finally.cs:49:9:51:9 | {...} | Finally.cs:50:13:50:40 | call to method WriteLine | 4 |
| Finally.cs:54:10:54:11 | enter M3 | Finally.cs:58:13:58:37 | call to method WriteLine | 7 |
| Finally.cs:54:10:54:11 | exit M3 | Finally.cs:54:10:54:11 | exit M3 | 1 |
| Finally.cs:54:10:54:11 | exit M3 (abnormal) | Finally.cs:54:10:54:11 | exit M3 (abnormal) | 1 |
| Finally.cs:54:10:54:11 | exit M3 (normal) | Finally.cs:54:10:54:11 | exit M3 (normal) | 1 |
| Finally.cs:59:13:59:19 | return ...; | Finally.cs:59:13:59:19 | return ...; | 1 |
| Finally.cs:61:9:64:9 | [exception: Exception] catch (...) {...} | Finally.cs:61:9:64:9 | [exception: Exception] catch (...) {...} | 1 |
| Finally.cs:61:38:61:39 | [exception: Exception] IOException ex | Finally.cs:61:48:61:51 | [exception: Exception] true | 2 |
| Finally.cs:61:9:64:9 | catch (...) {...} | Finally.cs:61:9:64:9 | catch (...) {...} | 1 |
| Finally.cs:61:38:61:39 | IOException ex | Finally.cs:61:48:61:51 | true | 2 |
| Finally.cs:62:9:64:9 | {...} | Finally.cs:63:13:63:18 | throw ...; | 2 |
| Finally.cs:65:9:67:9 | [exception: Exception] catch (...) {...} | Finally.cs:65:9:67:9 | [exception: Exception] catch (...) {...} | 1 |
| Finally.cs:65:26:65:26 | [exception: Exception] Exception e | Finally.cs:65:35:65:51 | [exception: Exception] ... != ... | 5 |
| Finally.cs:65:9:67:9 | catch (...) {...} | Finally.cs:65:9:67:9 | catch (...) {...} | 1 |
| Finally.cs:65:26:65:26 | Exception e | Finally.cs:65:35:65:51 | ... != ... | 5 |
| Finally.cs:66:9:67:9 | {...} | Finally.cs:66:9:67:9 | {...} | 1 |
| Finally.cs:69:9:71:9 | {...} | Finally.cs:70:13:70:40 | call to method WriteLine | 4 |
| Finally.cs:74:10:74:11 | enter M4 | Finally.cs:77:9:100:9 | while (...) ... | 6 |
Expand Down Expand Up @@ -490,10 +489,8 @@
| Finally.cs:158:36:158:36 | 1 | Finally.cs:158:21:158:36 | ... == ... | 2 |
| Finally.cs:159:21:159:45 | throw ...; | Finally.cs:159:21:159:45 | throw ...; | 1 |
| Finally.cs:159:41:159:43 | "1" | Finally.cs:159:27:159:44 | object creation of type Exception | 2 |
| Finally.cs:161:13:164:13 | [exception: Exception] catch (...) {...} | Finally.cs:161:13:164:13 | [exception: Exception] catch (...) {...} | 1 |
| Finally.cs:161:13:164:13 | [exception: NullReferenceException] catch (...) {...} | Finally.cs:161:13:164:13 | [exception: NullReferenceException] catch (...) {...} | 1 |
| Finally.cs:161:30:161:30 | [exception: Exception] Exception e | Finally.cs:161:39:161:54 | [exception: Exception] ... == ... | 5 |
| Finally.cs:161:30:161:30 | [exception: NullReferenceException] Exception e | Finally.cs:161:39:161:54 | [exception: NullReferenceException] ... == ... | 5 |
| Finally.cs:161:13:164:13 | catch (...) {...} | Finally.cs:161:13:164:13 | catch (...) {...} | 1 |
| Finally.cs:161:30:161:30 | Exception e | Finally.cs:161:39:161:54 | ... == ... | 5 |
| Finally.cs:162:13:164:13 | {...} | Finally.cs:163:17:163:42 | call to method WriteLine | 6 |
| Finally.cs:165:13:168:13 | catch {...} | Finally.cs:167:17:167:37 | call to method WriteLine | 5 |
| Finally.cs:172:11:172:20 | enter ExceptionA | Finally.cs:172:11:172:20 | exit ExceptionA | 5 |
Expand All @@ -506,11 +503,10 @@
| Finally.cs:180:21:180:43 | throw ...; | Finally.cs:180:21:180:43 | throw ...; | 1 |
| Finally.cs:180:27:180:42 | object creation of type ExceptionA | Finally.cs:180:27:180:42 | object creation of type ExceptionA | 1 |
| Finally.cs:183:9:192:9 | {...} | Finally.cs:186:21:186:22 | access to parameter b2 | 5 |
| Finally.cs:186:25:186:47 | throw ...; | Finally.cs:188:13:191:13 | [exception: ExceptionB] catch (...) {...} | 2 |
| Finally.cs:186:25:186:47 | throw ...; | Finally.cs:186:25:186:47 | throw ...; | 1 |
| Finally.cs:186:31:186:46 | object creation of type ExceptionB | Finally.cs:186:31:186:46 | object creation of type ExceptionB | 1 |
| Finally.cs:188:13:191:13 | [exception: Exception] catch (...) {...} | Finally.cs:188:13:191:13 | [exception: Exception] catch (...) {...} | 1 |
| Finally.cs:188:38:188:39 | [exception: ExceptionB] access to parameter b2 | Finally.cs:188:38:188:39 | [exception: ExceptionB] access to parameter b2 | 1 |
| Finally.cs:188:38:188:39 | [exception: Exception] access to parameter b2 | Finally.cs:188:38:188:39 | [exception: Exception] access to parameter b2 | 1 |
| Finally.cs:188:13:191:13 | catch (...) {...} | Finally.cs:188:13:191:13 | catch (...) {...} | 1 |
| Finally.cs:188:38:188:39 | access to parameter b2 | Finally.cs:188:38:188:39 | access to parameter b2 | 1 |
| Finally.cs:189:13:191:13 | {...} | Finally.cs:190:21:190:22 | access to parameter b1 | 3 |
| Finally.cs:190:31:190:46 | object creation of type ExceptionC | Finally.cs:190:25:190:47 | throw ...; | 2 |
| Finally.cs:195:10:195:12 | enter M10 | Finally.cs:199:17:199:18 | access to parameter b1 | 6 |
Expand Down
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