Merge pull request #1611 from charles-cooper/zero_pad

Fix termination condition in zero_pad
vyperlang · Sep 24, 2019 · 32ce6c9 · 32ce6c9
2 parents aa7a49e + 9a46479
commit 32ce6c9
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Showing 2 changed files with 13 additions and 4 deletions.
diff --git a/vyper/parser/events.py b/vyper/parser/events.py
@@ -108,9 +108,10 @@ def pack_args_by_32(holder, maxlen, arg, typ, context, placeholder,
             typ=typ, location='memory', annotation="pack_args_by_32:dest_placeholder")
         copier = make_byte_array_copier(dest_placeholder, source_lll, pos=pos)
         holder.append(copier)
+        item_maxlen = source_lll.typ.maxlen
         # Add zero padding.
         holder.append(
-            zero_pad(dest_placeholder, maxlen, zero_pad_i=zero_pad_i)
+            zero_pad(dest_placeholder, item_maxlen, zero_pad_i=zero_pad_i)
         )
 
         # Increment offset counter.

diff --git a/vyper/parser/parser_utils.py b/vyper/parser/parser_utils.py
@@ -889,19 +889,27 @@ def annotate_ast(
     RewriteUnarySubVisitor().visit(parsed_ast)
 
 
+# zero pad a bytearray according to the ABI spec. The last word
+# of the byte array needs to be right-padded with zeroes.
 def zero_pad(bytez_placeholder, maxlen, context=None, zero_pad_i=None):
     zero_padder = LLLnode.from_list(['pass'])
     if maxlen > 0:
         # Iterator used to zero pad memory.
         if zero_pad_i is None:
             zero_pad_i = context.new_placeholder(BaseType('uint256'))
         zero_padder = LLLnode.from_list([
-            'repeat', zero_pad_i, ['mload', bytez_placeholder], ceil32(maxlen), [
+            # the runtime length of the data rounded up to nearest 32
+            # from spec:
+            #   the actual value of X as a byte sequence,
+            #   followed by the *minimum* number of zero-bytes
+            #   such that len(enc(X)) is a multiple of 32.
+            'with', '_ceil32_end', ['ceil32', ['mload', bytez_placeholder]],
+            ['repeat', zero_pad_i, ['mload', bytez_placeholder], ceil32(maxlen), [
                 'seq',
                 # stay within allocated bounds
-                ['if', ['gt', ['mload', zero_pad_i], ceil32(maxlen)], 'break'],
+                ['if', ['ge', ['mload', zero_pad_i], '_ceil32_end'], 'break'],
                 ['mstore8', ['add', ['add', 32, bytez_placeholder], ['mload', zero_pad_i]], 0]
-            ]],
+                ]]],
             annotation="Zero pad",
         )
     return zero_padder