From 7da40757bd61d7c44c5344b6f0c2f07c22fe608d Mon Sep 17 00:00:00 2001
From: Josh Watson <josh@trailofbits.com>
Date: Mon, 1 Oct 2018 22:40:58 -0700
Subject: [PATCH 1/2] Improve exception handling Changed all Exception objects
 raised to more specific classes implemented in pyevmasm. Additionally,
 disassemble_all now catches a ParseError exception that could be thrown by
 Instruction.parse_operand, which would cause the generator to raise an
 exception instead of returning None.

---
 pyevmasm/evmasm.py | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/pyevmasm/evmasm.py b/pyevmasm/evmasm.py
index db42aff..42466da 100644
--- a/pyevmasm/evmasm.py
+++ b/pyevmasm/evmasm.py
@@ -35,6 +35,12 @@ class UnknownMnemonicError(Exception):
 class UnknownOpcodeError(Exception):
     pass
 
+class AssembleError(Exception):
+    pass
+
+class ParseError(Exception):
+    pass
+
 
 class InstructionTable(dict):
     """
@@ -365,7 +371,7 @@ def parse_operand(self, buf):
                 operand |= next(buf)
             self._operand = operand
         except StopIteration:
-            raise Exception("Not enough data for decoding")
+            raise ParseError("Not enough data for decoding")
 
     @property
     def operand_size(self):
@@ -557,8 +563,8 @@ def assemble_one(asmcode, pc=0):
             assert len(asmcode) == 2
             instr.operand = int(asmcode[1], 0)
         return instr
-    except BaseException:
-        raise Exception("Something wrong at pc %d" % pc)
+    except:
+        raise AssembleError("Something wrong at pc %d" % pc)
 
 
 def assemble_all(asmcode, pc=0):
@@ -627,10 +633,13 @@ def disassemble_one(bytecode, pc=0):
     instruction = instruction_table[opcode]
     instruction.pc = pc
 
-    if instruction.has_operand:
-        instruction.parse_operand(bytecode)
-
-    return instruction
+    try:
+        if instruction.has_operand:
+            instruction.parse_operand(bytecode)
+    except ParseError:
+        instruction = None
+    finally:
+        return instruction
 
 
 def disassemble_all(bytecode, pc=0):

From 49a118ef089d4d23f405408c1821ed594e15ae69 Mon Sep 17 00:00:00 2001
From: Josh Watson <josh@trailofbits.com>
Date: Mon, 1 Oct 2018 22:50:09 -0700
Subject: [PATCH 2/2] Make the `return` in `disassemble_all` explicit

Rather than just a `return` statement, `StopIteration` makes it clearer that the generator is done. They're functionally equivalent, but it's better for clarity in my opinion.
---
 pyevmasm/evmasm.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pyevmasm/evmasm.py b/pyevmasm/evmasm.py
index 42466da..7826da3 100644
--- a/pyevmasm/evmasm.py
+++ b/pyevmasm/evmasm.py
@@ -681,7 +681,7 @@ def disassemble_all(bytecode, pc=0):
     while True:
         instr = disassemble_one(bytecode, pc=pc)
         if not instr:
-            return
+            raise StopIteration
         pc += instr.size
         yield instr