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First pass at try-catch decompilation #930

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First pass at try-catch decompilation #930

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d48147b
Start work on try-catch decompilation
BenjaminUrquhart May 21, 2022
5ee7d6c
Merge branch 'master' of https://github.com/krzys-h/UndertaleModTool
BenjaminUrquhart May 21, 2022
a21eed9
Merge branch 'master' of https://github.com/krzys-h/UndertaleModTool
BenjaminUrquhart May 31, 2022
79e50cc
Merge branch 'master' of https://github.com/krzys-h/UndertaleModTool
BenjaminUrquhart Jun 20, 2022
78ba8a2
Merge branch 'master' of https://github.com/krzys-h/UndertaleModTool
BenjaminUrquhart Oct 4, 2022
dac2bac
Merge branch 'master' of https://github.com/krzys-h/UndertaleModTool
BenjaminUrquhart Dec 4, 2022
83a6b7f
Merge branch 'master' of https://github.com/krzys-h/UndertaleModTool
BenjaminUrquhart Dec 8, 2023
6342ef2
Merge pull request #1 from Jacky720/version-check-fix
BenjaminUrquhart Dec 10, 2023
3e709eb
Merge branch 'master' of https://github.com/krzys-h/UndertaleModTool
BenjaminUrquhart Dec 23, 2023
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194 changes: 178 additions & 16 deletions UndertaleModLib/Decompiler/Decompiler.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -1379,6 +1379,32 @@ internal override AssetIDType DoTypePropagation(DecompileContext context, AssetI
}
}

public class TempExceptionValue : Expression
{
private Block tryBlock, catchBlock;

public TempExceptionValue(Block tryBlock, Block catchBlock)
{
this.catchBlock = catchBlock;
this.tryBlock = tryBlock;
}

public override Statement CleanStatement(DecompileContext context, BlockHLStatement block)
{
return this;
}

public override string ToString(DecompileContext context)
{
return "// TempExceptionValue " + tryBlock + " " + catchBlock;
}

internal override AssetIDType DoTypePropagation(DecompileContext context, AssetIDType suggestedType)
{
return suggestedType;
}
}

// Represents a high-level operation-equals statement, such as a += 1.
public class OperationEqualsStatement : Statement
{
Expand Down Expand Up @@ -1713,6 +1739,11 @@ cast.Argument is ExpressionConstant constant &&

return String.Format("new {0}({1})", constructor, argumentString);
}
else if (Function.Name.Content == "@@throw@@" && Arguments.Count == 1)
{
context.currentFunction = this;
return "throw " + Arguments[0].ToString(context);
}
else
{
foreach (Expression exp in Arguments)
Expand All @@ -1728,7 +1759,12 @@ cast.Argument is ExpressionConstant constant &&
if (Function.Name.Content == "@@NewGMLArray@@") // Inline array definitions
return "[" + argumentString.ToString() + "]";

return String.Format("{0}({1})", OverridenName != string.Empty ? OverridenName : Function.Name.Content, argumentString.ToString());
string ret = String.Format("{0}({1})", OverridenName != string.Empty ? OverridenName : Function.Name.Content, argumentString.ToString());

if (ret.StartsWith("@@try_") || ret.StartsWith("@@finish_"))
return "// " + ret;

return ret;
}
}

Expand Down Expand Up @@ -2371,7 +2407,7 @@ internal static void DecompileFromBlock(DecompileContext context, Dictionary<uin
target.InstType = stack.Pop();
}

if (instr.Type1 == UndertaleInstruction.DataType.Variable)
if (instr.Type1 == UndertaleInstruction.DataType.Variable && stack.Count > 0)
val = stack.Pop();
if (val != null)
{
Expand Down Expand Up @@ -2505,20 +2541,25 @@ internal static void DecompileFromBlock(DecompileContext context, Dictionary<uin
case UndertaleInstruction.Opcode.Call:
{
List<Expression> args = new List<Expression>();
List<Expression> cleanArgs = new List<Expression>();
Expression arg;
for (int j = 0; j < instr.ArgumentsCount; j++)
args.Add(stack.Pop());
{
arg = stack.Pop();
args.Add(arg);

while (arg is ExpressionCast cast)
arg = cast.Argument;

cleanArgs.Add(arg);
}

if (instr.Function.Target.Name.Content == "method" && args.Count == 2)
{
// Special case - method creation
// See if the body should be inlined

Expression arg1 = args[0];
while (arg1 is ExpressionCast cast)
arg1 = cast.Argument;
Expression arg2 = args[1];
while (arg2 is ExpressionCast cast)
arg2 = cast.Argument;
Expression arg1 = cleanArgs[0], arg2 = cleanArgs[1];

if (arg2 is ExpressionConstant argCode && argCode.Type == UndertaleInstruction.DataType.Int32 &&
argCode.Value is UndertaleInstruction.Reference<UndertaleFunction> argCodeFunc)
Expand Down Expand Up @@ -2547,6 +2588,51 @@ internal static void DecompileFromBlock(DecompileContext context, Dictionary<uin
}
}
}
else if (instr.Function.Target.Name.Content == "@@try_hook@@" && args.Count == 2)
{
Block tryBlock = block.nextBlockFalse, catchBlock = null, tmp = block.nextBlockFalse;

string catchStr = cleanArgs[0].ToString(context), endStr = cleanArgs[1].ToString(context);
if (!uint.TryParse(catchStr, out uint catchAddr) || !uint.TryParse(endStr, out uint endAddr))
throw new InvalidDataException("Bad arguments to @@try_hook@@: " + catchStr + " " + endStr);

catchAddr /= 4;
endAddr /= 4;

catchBlock = blocks[catchAddr];

// Find first block that's not in the try block
tmp = blocks[endAddr];

// Set up a temporary reference as a placeholder
// value for the localvar that holds the exception
// in the catch block.

var vars = new List<TempVarReference>();
TempVar tempVar = context.NewTempVar();
TempVarReference varRef = new TempVarReference(tempVar);
context.TempVarMap[tempVar.Name] = new TempVarAssignmentStatement(varRef, new TempExceptionValue(tryBlock, catchBlock));
vars.Add(varRef);

//catchBlock.TempVarsOnEntry ??= new();
//tryBlock.TempVarsOnEntry ??= new();

//catchBlock.TempVarsOnEntry.Add(varRef);
//tryBlock.TempVarsOnEntry.Add(varRef);

// Decompile the try and catch blocks

workQueue.Push(new Tuple<Block, List<TempVarReference>>(catchBlock, vars));
workQueue.Push(new Tuple<Block, List<TempVarReference>>(tryBlock, new List<TempVarReference>()));

statements.Add(new TryCatchHLStatement(tryBlock, catchBlock));
stack.Push(new TempExceptionValue(tryBlock, catchBlock));
//stack.Push(new TempExceptionValue(tryBlock));
block.nextBlockFalse = null;
block.nextBlockTrue = tmp;
break;

}

UndertaleCode callTargetBody = context.GlobalContext.Data?.Code.FirstOrDefault(x => x.Name.Content == instr.Function.Target.Name.Content);
if (callTargetBody != null && callTargetBody.ParentEntry != null && !context.DisableAnonymousFunctionNameResolution)
Expand Down Expand Up @@ -2735,14 +2821,21 @@ assign.Value is FunctionDefinition funcDef &&
List<TempVarReference> leftovers = new List<TempVarReference>();
for (int i = stack.Count - 1; i >= 0; i--)
{
if (i < tempvars.Count)
Expression val = stack.Pop();

// Skip throw statements; they don't have a corresponding pop instruction,
// within their block (as far as I can tell), so they will always leak onto the stack.
if (val is DirectFunctionCall call && call.Function.Name.Content == "@@throw@@" && call.Arguments.Count == 1)
statements.Add(val);
else if (i < tempvars.Count)
{
Expression val = stack.Pop();
if (!(val is ExpressionTempVar) || (val as ExpressionTempVar).Var != tempvars[i]) {
if (!(val is ExpressionTempVar) || (val as ExpressionTempVar).Var != tempvars[i])
{
var assignment = new TempVarAssignmentStatement(tempvars[i], val);
statements.Add(assignment);

if (val is ExpressionConstant) {
if (val is ExpressionConstant)
{
context.TempVarMap[tempvars[i].Var.Name] = assignment;
}
}
Expand All @@ -2751,15 +2844,15 @@ assign.Value is FunctionDefinition funcDef &&
}
else
{
Expression val = stack.Pop();
TempVar var = context.NewTempVar();
var.Type = val.Type;
TempVarReference varref = new TempVarReference(var);
var assignment = new TempVarAssignmentStatement(varref, val);
statements.Add(assignment);
leftovers.Add(varref);

if (val is ExpressionConstant) {
if (val is ExpressionConstant)
{
context.TempVarMap[var.Name] = assignment;
}
}
Expand Down Expand Up @@ -2803,8 +2896,17 @@ public static Dictionary<uint, Block> DecompileFlowGraph(UndertaleCode code, Lis
blockByAddress[code.Length / 4] = finalBlock;
Block currentBlock = entryBlock;

int index = -1;
bool skip = false;
foreach (var instr in code.Instructions)
{
index++;
if (skip)
{
skip = false;
continue;
}

if (blockByAddress.ContainsKey(instr.Address))
{
if (currentBlock != null)
Expand Down Expand Up @@ -2909,6 +3011,20 @@ public static Dictionary<uint, Block> DecompileFlowGraph(UndertaleCode code, Lis
currentBlock.nextBlockFalse = nextBlock;
currentBlock = null;
}
else if (instr.Kind == UndertaleInstruction.Opcode.Call && instr.Function?.Target.Name.Content == "@@try_hook@@")
{
UndertaleInstruction next;
if(code.Instructions.Count > index + 1 && (next = code.Instructions[index + 1]).Kind == UndertaleInstruction.Opcode.Popz)
{
skip = true;
Block nextBlock = GetBlock(next.Address + 1);
currentBlock.Instructions.Add(next);
currentBlock.conditionalExit = false;
currentBlock.nextBlockTrue = nextBlock;
currentBlock.nextBlockFalse = nextBlock;
currentBlock = null;
}
}
}
if (currentBlock != null)
{
Expand Down Expand Up @@ -2999,6 +3115,52 @@ private static bool CanSkipBrackets(BlockHLStatement blockStatement)
}
};

public class TryCatchHLStatement : BlockHLStatement
{
public Block tryBlock, catchBlock;

public TryCatchHLStatement(Block tryBlock, Block catchBlock = null)
{
this.catchBlock = catchBlock;
this.tryBlock = tryBlock;
}

public new BlockHLStatement CleanBlockStatement(DecompileContext context)
{
if (tryBlock.Statements != null)
Statements = tryBlock.Statements;
return base.CleanBlockStatement(context);
}

internal override AssetIDType DoTypePropagation(DecompileContext context, AssetIDType suggestedType)
{
return suggestedType;
}

public override string ToString(DecompileContext context)
{
StringBuilder sb = new StringBuilder();
Statements = tryBlock.Statements;
sb.AppendLine("try");
sb.Append(context.Indentation);
sb.AppendLine(ToString(context, false));

if (catchBlock != null)
{
Statements = catchBlock.Statements.Skip(1).ToList();
sb.Append(context.Indentation);
sb.Append("catch(");
sb.Append(catchBlock.Instructions[0].Destination.Target.Name.Content);
sb.AppendLine(")");
sb.Append(context.Indentation);
sb.AppendLine(ToString(context, false));
Statements = tryBlock.Statements;
}

return sb.ToString();
}
}

public class IfHLStatement : HLStatement
{
public Expression condition;
Expand Down Expand Up @@ -3595,7 +3757,7 @@ private static BlockHLStatement HLDecompileBlocks(DecompileContext context, ref
if (depth > 200)
throw new Exception("Excessive recursion while processing blocks.");

BlockHLStatement output = new BlockHLStatement();
BlockHLStatement output = new BlockHLStatement();

Block lastBlock = null;
bool popenvDrop = false;
Expand Down
10 changes: 10 additions & 0 deletions UndertaleModLib/Decompiler/Disassembler.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -82,8 +82,10 @@ public static List<uint> FindBlockAddresses(UndertaleCode code)
if (code.Instructions.Count != 0)
addresses.Add(0);

int index = -1;
foreach (var inst in code.Instructions)
{
index++;
switch (inst.Kind)
{
case UndertaleInstruction.Opcode.B:
Expand All @@ -101,6 +103,14 @@ public static List<uint> FindBlockAddresses(UndertaleCode code)
case UndertaleInstruction.Opcode.Ret:
addresses.Add(inst.Address + 1);
break;
case UndertaleInstruction.Opcode.Call:
if (inst.Function?.Target.Name.Content == "@@try_hook@@" && code.Instructions.Count > index + 1)
{
UndertaleInstruction next = code.Instructions[index + 1];
if (next.Kind == UndertaleInstruction.Opcode.Popz)
addresses.Add(next.Address + 1);
}
break;
}
}

Expand Down
4 changes: 4 additions & 0 deletions UndertaleModTool/Resources/GML.xshd
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Original file line number Diff line number Diff line change
Expand Up @@ -45,6 +45,10 @@
<Word>continue</Word>
<Word>with</Word>
<Word>new</Word>
<Word>throw</Word>
<Word>try</Word>
<Word>catch</Word>
<Word>finally</Word>
<Word>constructor</Word>
<Word>function</Word>
<Word>return</Word>
Expand Down
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