From 5a10cf3506f56d62f6bd2dd4cc4c37587f1a5c70 Mon Sep 17 00:00:00 2001
From: Jesse Plamondon-Willard <Pathoschild@users.noreply.github.com>
Date: Wed, 16 Sep 2020 18:03:25 -0400
Subject: fix error when a mod rewrite adds instructions that break a short
 jump

---
 .../ModLoading/Framework/RecursiveRewriter.cs      | 20 +++++++++++++++++-
 .../ModLoading/Framework/RewriteHelper.cs          | 24 ++++++++++++++++++++++
 2 files changed, 43 insertions(+), 1 deletion(-)

(limited to 'src/SMAPI/Framework/ModLoading')

diff --git a/src/SMAPI/Framework/ModLoading/Framework/RecursiveRewriter.cs b/src/SMAPI/Framework/ModLoading/Framework/RecursiveRewriter.cs
index ea29550a..10f68f0d 100644
--- a/src/SMAPI/Framework/ModLoading/Framework/RecursiveRewriter.cs
+++ b/src/SMAPI/Framework/ModLoading/Framework/RecursiveRewriter.cs
@@ -111,21 +111,39 @@ namespace StardewModdingAPI.Framework.ModLoading.Framework
                     foreach (VariableDefinition variable in method.Body.Variables)
                         changed |= this.RewriteTypeReference(variable.VariableType, newType => variable.VariableType = newType);
 
-                    // check CIL instructions
+                    // rewrite CIL instructions
                     ILProcessor cil = method.Body.GetILProcessor();
                     Collection<Instruction> instructions = cil.Body.Instructions;
+                    bool addedInstructions = false;
                     for (int i = 0; i < instructions.Count; i++)
                     {
                         var instruction = instructions[i];
                         if (instruction.OpCode.Code == Code.Nop)
                             continue;
 
+                        int oldCount = cil.Body.Instructions.Count;
                         changed |= this.RewriteInstruction(instruction, cil, newInstruction =>
                         {
                             changed = true;
                             cil.Replace(instruction, newInstruction);
                             instruction = newInstruction;
                         });
+
+                        if (cil.Body.Instructions.Count > oldCount)
+                            addedInstructions = true;
+                    }
+
+                    // special case: added instructions may cause an instruction to be out of range
+                    // of a short jump that references it
+                    if (addedInstructions)
+                    {
+                        foreach (var instruction in instructions)
+                        {
+                            var longJumpCode = RewriteHelper.GetEquivalentLongJumpCode(instruction.OpCode);
+                            if (longJumpCode != null)
+                                instruction.OpCode = longJumpCode.Value;
+                        }
+                        changed = true;
                     }
                 }
             }
diff --git a/src/SMAPI/Framework/ModLoading/Framework/RewriteHelper.cs b/src/SMAPI/Framework/ModLoading/Framework/RewriteHelper.cs
index 207b6445..1f7834ce 100644
--- a/src/SMAPI/Framework/ModLoading/Framework/RewriteHelper.cs
+++ b/src/SMAPI/Framework/ModLoading/Framework/RewriteHelper.cs
@@ -77,6 +77,30 @@ namespace StardewModdingAPI.Framework.ModLoading.Framework
             };
         }
 
+        /// <summary>Get the long equivalent for a short-jump op code.</summary>
+        /// <param name="shortJumpCode">The short-jump op code.</param>
+        /// <returns>Returns the instruction, or <c>null</c> if it isn't a short jump.</returns>
+        public static OpCode? GetEquivalentLongJumpCode(OpCode shortJumpCode)
+        {
+            return shortJumpCode.Code switch
+            {
+                Code.Beq_S => OpCodes.Beq,
+                Code.Bge_S => OpCodes.Bge,
+                Code.Bge_Un_S => OpCodes.Bge_Un,
+                Code.Bgt_S => OpCodes.Bgt,
+                Code.Bgt_Un_S => OpCodes.Bgt_Un,
+                Code.Ble_S => OpCodes.Ble,
+                Code.Ble_Un_S => OpCodes.Ble_Un,
+                Code.Blt_S => OpCodes.Blt,
+                Code.Blt_Un_S => OpCodes.Blt_Un,
+                Code.Bne_Un_S => OpCodes.Bne_Un,
+                Code.Br_S => OpCodes.Br,
+                Code.Brfalse_S => OpCodes.Brfalse,
+                Code.Brtrue_S => OpCodes.Brtrue,
+                _ => null
+            };
+        }
+
         /// <summary>Get whether a type matches a type reference.</summary>
         /// <param name="type">The defined type.</param>
         /// <param name="reference">The type reference.</param>
-- 
cgit