Skip to content

Consider an invalid instruction the end of a function trace #11

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
KallDrexx merged 1 commit into from
Oct 12, 2025
Merged

Consider an invalid instruction the end of a function trace #11

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
14 changes: 11 additions & 3 deletions NESDecompiler.Core/Decompilation/FunctionDecompiler.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -56,6 +56,13 @@ public static DecompiledFunction Decompile(ushort functionAddress, IReadOnlyList
}

var instruction = GetNextInstruction(nextAddress, codeRegions);
if (instruction == null)
{
// Consider no instruction the end of the function. This is usually the case
// with an always taken branch
continue;
}

instructions.Add(instruction);

// Ensure the function entrypoint has a label
Expand Down Expand Up @@ -94,7 +101,7 @@ public static DecompiledFunction Decompile(ushort functionAddress, IReadOnlyList
return new DecompiledFunction(functionAddress, instructions, jumpAddresses);
}

private static DisassembledInstruction GetNextInstruction(ushort address, IReadOnlyList<CodeRegion> regions)
private static DisassembledInstruction? GetNextInstruction(ushort address, IReadOnlyList<CodeRegion> regions)
{
var relevantRegion = regions
.Where(x => x.BaseAddress < address)
Expand All @@ -112,8 +119,9 @@ private static DisassembledInstruction GetNextInstruction(ushort address, IReadO
var info = InstructionSet.GetInstruction(bytes[0]);
if (!info.IsValid)
{
var message = $"Opcode 0x{bytes[0]:X2} at address 0x{address:X4} is not a known instruction";
throw new InvalidOperationException(message);
var message = $"Warning: encountered unknown op code 0x{bytes[0]:X2} at address 0x{address:X4}";
Console.WriteLine(message);
return null;
}

if (bytes.Length < info.Size)
Expand Down
Loading