private static void WriteFinalizers(ILEmitter il, MethodBase original, ILEmitter.Label returnLabel,
Dictionary <string, VariableDefinition> variables,
List <MethodInfo> finalizers)
{
// Finalizer layout:
// Create __exception variable to store exception info and a skip flag
// Wrap the whole method into a try/catch
// Call finalizers at the end of method (simulate `finally`)
// If __exception got set, throw it
// Begin catch block
// Store exception into __exception
// If skip flag is set, skip finalizers
// Call finalizers
// If __exception is still set, rethrow (if new exception set, otherwise throw the new exception)
// End catch block
if (finalizers.Count == 0)
{
return;
}
Logger.Log(Logger.LogChannel.Info, () => "Writing finalizers");
il.emitBefore = il.IL.Body.Instructions[il.IL.Body.Instructions.Count - 1];
// Mark the original method return label here if it hasn't been yet
il.MarkLabel(returnLabel);
if (!variables.TryGetValue(RESULT_VAR, out var returnValueVar))
{
var retVal = AccessTools.GetReturnedType(original);
returnValueVar = variables[RESULT_VAR] = retVal == typeof(void) ? null : il.DeclareVariable(retVal);
}
// Create variables to hold custom exception
var skipFinalizersVar = il.DeclareVariable(typeof(bool));
variables[EXCEPTION_VAR] = il.DeclareVariable(typeof(Exception));
// Start main exception block
var mainBlock = il.BeginExceptionBlock(il.DeclareLabelFor(il.IL.Body.Instructions[0]));
bool WriteFinalizerCalls(bool suppressExceptions)
{
var canRethrow = true;
foreach (var finalizer in finalizers)
{
var start = il.DeclareLabel();
il.MarkLabel(start);
EmitCallParameter(il, original, finalizer, variables, false);
il.Emit(OpCodes.Call, finalizer);
if (finalizer.ReturnType != typeof(void))
{
il.Emit(OpCodes.Stloc, variables[EXCEPTION_VAR]);
canRethrow = false;
}
if (suppressExceptions)
{
var exBlock = il.BeginExceptionBlock(start);
il.BeginHandler(exBlock, ExceptionHandlerType.Catch, typeof(object));
il.Emit(OpCodes.Pop);
il.EndExceptionBlock(exBlock);
}
}
return(canRethrow);
}
// First, store potential result into a variable and empty the stack
if (returnValueVar != null)
{
il.Emit(OpCodes.Stloc, returnValueVar);
}
// Write finalizers inside the `try`
WriteFinalizerCalls(false);
// Mark finalizers as skipped so they won't rerun
il.Emit(OpCodes.Ldc_I4_1);
il.Emit(OpCodes.Stloc, skipFinalizersVar);
// If __exception is not null, throw
var skipLabel = il.DeclareLabel();
il.Emit(OpCodes.Ldloc, variables[EXCEPTION_VAR]);
il.Emit(OpCodes.Brfalse, skipLabel);
il.Emit(OpCodes.Ldloc, variables[EXCEPTION_VAR]);
il.Emit(OpCodes.Throw);
il.MarkLabel(skipLabel);
// Begin a generic `catch(Exception o)` here and capture exception into __exception
il.BeginHandler(mainBlock, ExceptionHandlerType.Catch, typeof(Exception));
il.Emit(OpCodes.Stloc, variables[EXCEPTION_VAR]);
// Call finalizers or skip them if needed
il.Emit(OpCodes.Ldloc, skipFinalizersVar);
var postFinalizersLabel = il.DeclareLabel();
il.Emit(OpCodes.Brtrue, postFinalizersLabel);
var rethrowPossible = WriteFinalizerCalls(true);
il.MarkLabel(postFinalizersLabel);
// Possibly rethrow if __exception is still not null (i.e. suppressed)
skipLabel = il.DeclareLabel();
il.Emit(OpCodes.Ldloc, variables[EXCEPTION_VAR]);
il.Emit(OpCodes.Brfalse, skipLabel);
if (rethrowPossible)
{
il.Emit(OpCodes.Rethrow);
}
else
{
il.Emit(OpCodes.Ldloc, variables[EXCEPTION_VAR]);
il.Emit(OpCodes.Throw);
}
il.MarkLabel(skipLabel);
il.EndExceptionBlock(mainBlock);
if (returnValueVar != null)
{
il.Emit(OpCodes.Ldloc, returnValueVar);
}
}