From 7bc3105115dbdd8114b38a753b1a8dd6d8e85dcb Mon Sep 17 00:00:00 2001
From: Abinav Puthan Purayil <abinavpp@gmail.com>
Date: Sat, 1 Jun 2024 22:18:36 +0200
Subject: [PATCH] [0.8.7] Fix the try-catch lowering hack (#648)

---
 libsolidity/ast/ASTAnnotations.h           |  7 +++++++
 libsolidity/codegen/CompilerContext.h      |  5 -----
 libsolidity/codegen/ContractCompiler.cpp   | 12 +++++++++---
 libsolidity/codegen/ExpressionCompiler.cpp | 12 ++++++++----
 libsolidity/codegen/ExpressionCompiler.h   |  3 ++-
 5 files changed, 26 insertions(+), 13 deletions(-)

diff --git a/libsolidity/ast/ASTAnnotations.h b/libsolidity/ast/ASTAnnotations.h
index 6b4b14e7c7..4e1b823f9d 100644
--- a/libsolidity/ast/ASTAnnotations.h
+++ b/libsolidity/ast/ASTAnnotations.h
@@ -331,6 +331,13 @@ struct FunctionCallAnnotation: ExpressionAnnotation
 	util::SetOnce<FunctionCallKind> kind;
 	/// If true, this is the external call of a try statement.
 	bool tryCall = false;
+
+	// HACK!
+	// We track the success tag here for the `TryStatement` lowering. This is to avoid the redundant status check and
+	// the conditional jump. Such patterns can confuse the zksolc translator.
+	//
+	// uint32_t since Assembly::new[Push]Tag() asserts that the tag is 32 bits.
+	std::optional<uint32_t> tryCallSuccessTag;
 };
 
 }
diff --git a/libsolidity/codegen/CompilerContext.h b/libsolidity/codegen/CompilerContext.h
index 0bb020df1c..f2bb0be899 100644
--- a/libsolidity/codegen/CompilerContext.h
+++ b/libsolidity/codegen/CompilerContext.h
@@ -348,11 +348,6 @@ class CompilerContext
 
 	RevertStrings revertStrings() const { return m_revertStrings; }
 
-	// HACK!
-	// We track the success tag here for the `TryStatement` lowering. This is to avoid the redundant status check and
-	// the conditional jump. Such patterns can confuse the zksolc translator.
-	evmasm::AssemblyItem currTryCallSuccessTag{evmasm::AssemblyItemType::UndefinedItem};
-
 private:
 	/// Updates source location set in the assembly.
 	void updateSourceLocation();
diff --git a/libsolidity/codegen/ContractCompiler.cpp b/libsolidity/codegen/ContractCompiler.cpp
index 888cef0c4d..bdfb33937c 100644
--- a/libsolidity/codegen/ContractCompiler.cpp
+++ b/libsolidity/codegen/ContractCompiler.cpp
@@ -979,7 +979,10 @@ bool ContractCompiler::visit(TryStatement const& _tryStatement)
 	StackHeightChecker checker(m_context);
 	CompilerContext::LocationSetter locationSetter(m_context, _tryStatement);
 
-	compileExpression(_tryStatement.externalCall());
+	auto* externalCall = dynamic_cast<FunctionCall const*>(&_tryStatement.externalCall());
+	solAssert(externalCall && externalCall->annotation().tryCall, "");
+	compileExpression(*externalCall);
+
 	int const returnSize = static_cast<int>(_tryStatement.externalCall().annotation().type->sizeOnStack());
 
 	// Stack: [ return values] <success flag>
@@ -992,8 +995,11 @@ bool ContractCompiler::visit(TryStatement const& _tryStatement)
 
 	evmasm::AssemblyItem endTag = m_context.appendJumpToNew();
 
-	solAssert(m_context.currTryCallSuccessTag.type() == AssemblyItemType::Tag, "");
-	m_context << m_context.currTryCallSuccessTag;
+	auto& successTag = externalCall->annotation().tryCallSuccessTag;
+	solAssert(successTag, "");
+	m_context << AssemblyItem(AssemblyItemType::Tag, *successTag);
+	successTag.reset();
+
 	m_context.adjustStackOffset(returnSize);
 	{
 		// Success case.
diff --git a/libsolidity/codegen/ExpressionCompiler.cpp b/libsolidity/codegen/ExpressionCompiler.cpp
index 720b8317c5..2a8a895d0b 100644
--- a/libsolidity/codegen/ExpressionCompiler.cpp
+++ b/libsolidity/codegen/ExpressionCompiler.cpp
@@ -761,7 +761,8 @@ bool ExpressionCompiler::visit(FunctionCall const& _functionCall)
 		case FunctionType::Kind::External:
 		case FunctionType::Kind::DelegateCall:
 			_functionCall.expression().accept(*this);
-			appendExternalFunctionCall(function, arguments, _functionCall.annotation().tryCall);
+			appendExternalFunctionCall(
+				function, arguments, _functionCall.annotation().tryCall, &_functionCall.annotation());
 			break;
 		case FunctionType::Kind::BareCallCode:
 			solAssert(false, "Callcode has been removed.");
@@ -821,7 +822,8 @@ bool ExpressionCompiler::visit(FunctionCall const& _functionCall)
 				// If this is a try call, return "<address> 1" in the success case and
 				// "0" in the error case.
 				AssemblyItem errorCase = m_context.appendConditionalJump();
-				m_context.currTryCallSuccessTag = m_context.appendJumpToNew();
+				_functionCall.annotation().tryCallSuccessTag
+					= m_context.appendJumpToNew().data().convert_to<uint32_t>();
 				m_context.adjustStackOffset(1);
 				m_context << errorCase;
 			}
@@ -2514,7 +2516,8 @@ void ExpressionCompiler::appendExpOperatorCode(Type const& _valueType, Type cons
 void ExpressionCompiler::appendExternalFunctionCall(
 	FunctionType const& _functionType,
 	vector<ASTPointer<Expression const>> const& _arguments,
-	bool _tryCall
+	bool _tryCall,
+	FunctionCallAnnotation* _annotation
 )
 {
 	solAssert(
@@ -2792,8 +2795,9 @@ void ExpressionCompiler::appendExternalFunctionCall(
 
 	if (_tryCall)
 	{
+		solAssert(_annotation, "");
 		// Success branch will reach this, failure branch will directly jump to endTag.
-		m_context.currTryCallSuccessTag = m_context.appendJumpToNew();
+		_annotation->tryCallSuccessTag = m_context.appendJumpToNew().data().convert_to<uint32_t>();
 		m_context.adjustStackOffset(1);
 		m_context << endTag;
 	}
diff --git a/libsolidity/codegen/ExpressionCompiler.h b/libsolidity/codegen/ExpressionCompiler.h
index cfa36de4bc..0ba13f8258 100644
--- a/libsolidity/codegen/ExpressionCompiler.h
+++ b/libsolidity/codegen/ExpressionCompiler.h
@@ -110,7 +110,8 @@ class ExpressionCompiler: private ASTConstVisitor
 	void appendExternalFunctionCall(
 		FunctionType const& _functionType,
 		std::vector<ASTPointer<Expression const>> const& _arguments,
-		bool _tryCall
+		bool _tryCall,
+		FunctionCallAnnotation* _annotation = nullptr
 	);
 	/// Appends code that evaluates a single expression and moves the result to memory. The memory offset is
 	/// expected to be on the stack and is updated by this call.