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Bugfix attempt for mismatched jump labels by IlProcessor #77

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Bugfix attempt for mismatched jump labels by IlProcessor #77

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20 changes: 17 additions & 3 deletions Harmony/Internal/Patching/ILManipulator.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -347,9 +347,7 @@ public void WriteTo(MethodBody body, MethodBase original = null)

// We need to handle exception handler opcodes specially because ILProcessor emits them automatically
// Case 1: leave + start or end of exception block => ILProcessor generates leave automatically
if ((cur.opcode == SRE.OpCodes.Leave || cur.opcode == SRE.OpCodes.Leave_S) &&
(cur.blocks.Count > 0 || next?.blocks.Count > 0))
goto mark_block;
// Note: ILProcessor seems to generate some labels with wrong offset, clean-up code afterwards!
// Case 2: endfilter/endfinally and end of exception marker => ILProcessor will generate the correct end
if ((cur.opcode == SRE.OpCodes.Endfilter || cur.opcode == SRE.OpCodes.Endfinally) && cur.blocks.Count > 0)
goto mark_block;
Expand Down Expand Up @@ -380,6 +378,22 @@ public void WriteTo(MethodBody body, MethodBase original = null)
cur.blocks.ForEach(b => il.MarkBlockAfter(b));
}

// Remove duplicate `leave` Op-Codes to cleanup
// Should be safe if "double-jumps" are not a thing
for (int i = 0; i < body.Instructions.Count - 1; i++)
{
// Find two leave instructions in a row to clean up
if (body.Instructions[i].OpCode != OpCodes.Leave &&
body.Instructions[i].OpCode != OpCodes.Leave_S) continue;
if (body.Instructions[i + 1].OpCode != OpCodes.Leave &&
body.Instructions[i + 1].OpCode != OpCodes.Leave_S) continue;
// Not exactly sure why this happens, labels should agree here!?
// if (body.Instructions[i].Offset != body.Instructions[i + 1].Offset)
// Logger.Log(Logger.LogChannel.Warn, () =>
// "Found conescutive leave ops that don't agree");
body.Instructions.RemoveAt(i + 1);
}

// Special Harmony interop case: if no instructions exist, at least emit a quick return to attempt to get a valid method
// Vanilla Harmony (almost) always emits a `ret` which allows for skipping original method by writing an empty transpiler
if (body.Instructions.Count == 0)
Expand Down