Merge pull request #13001 from matheusaaguiar/develop

Don't add an empty data slot to ABI-encoded empty strings from storage

Author: chriseth

Changelog.md

@@ -8,6 +8,7 @@ Compiler Features:
 
 
 Bugfixes:
+ * ABI Encoder: When encoding an empty string coming from storage do not add a superfluous empty slot for data.
 
 
 ### 0.8.14 (2022-05-17)

libsolidity/codegen/ABIFunctions.cpp

@@ -699,7 +699,7 @@ string ABIFunctions::abiEncodingFunctionCompactStorageArray(
 					case 0 {
 						// short byte array
 						mstore(pos, and(slotValue, not(0xff)))
-						ret := add(pos, <lengthPaddedShort>)
+						ret := add(pos, mul(<lengthPaddedShort>, iszero(iszero(length))))
 					}
 					case 1 {
 						// long byte array

test/libsolidity/semanticTests/array/copying/bytes_storage_to_storage.sol

@@ -17,7 +17,7 @@ contract c {
 // ----
 // f(uint256): 0 -> 0x20, 0x00
 // f(uint256): 31 -> 0x20, 0x1f, 0x0102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e00
-// gas irOptimized: 121735
+// gas irOptimized: 121752
 // gas legacy: 123884
 // gas legacyOptimized: 119139
 // f(uint256): 32 -> 0x20, 0x20, 1780731860627700044960722568376592200742329637303199754547598369979440671

test/libsolidity/semanticTests/array/copying/copy_byte_array_in_struct_to_storage.sol

@@ -35,11 +35,11 @@ contract C {
 }
 // ----
 // f() -> 0x40, 0x80, 6, 0x6162636465660000000000000000000000000000000000000000000000000000, 0x49, 0x3132333435363738393031323334353637383930313233343536373839303120, 0x3132333435363738393031323334353637383930313233343536373839303120, 0x3132333435363738390000000000000000000000000000000000000000000000
-// gas irOptimized: 179895
+// gas irOptimized: 179912
 // gas legacy: 180676
 // gas legacyOptimized: 180070
 // g() -> 0x40, 0xc0, 0x49, 0x3132333435363738393031323334353637383930313233343536373839303120, 0x3132333435363738393031323334353637383930313233343536373839303120, 0x3132333435363738390000000000000000000000000000000000000000000000, 0x11, 0x3132333435363738393233343536373839000000000000000000000000000000
-// gas irOptimized: 107274
+// gas irOptimized: 107291
 // gas legacy: 107877
 // gas legacyOptimized: 107236
 // h() -> 0x40, 0x60, 0x00, 0x00

test/libsolidity/semanticTests/array/copying/storage_memory_nested_bytes.sol

@@ -11,6 +11,6 @@ contract C {
 }
 // ----
 // f() -> 0x20, 0x02, 0x40, 0x80, 3, 0x6162630000000000000000000000000000000000000000000000000000000000, 0x99, 44048183304486788312148433451363384677562265908331949128489393215789685032262, 32241931068525137014058842823026578386641954854143559838526554899205067598957, 49951309422467613961193228765530489307475214998374779756599339590522149884499, 0x54555658595a6162636465666768696a6b6c6d6e6f707172737475767778797a, 0x4142434445464748494a4b4c4d4e4f5051525354555658595a00000000000000
-// gas irOptimized: 202840
+// gas irOptimized: 202864
 // gas legacy: 204441
 // gas legacyOptimized: 203419

test/libsolidity/semanticTests/array/pop/byte_array_pop_copy_long.sol

@@ -10,6 +10,6 @@ contract c {
 
 // ----
 // test() -> 0x20, 29, 0x0303030303030303030303030303030303030303030303030303030303000000
-// gas irOptimized: 109499
+// gas irOptimized: 109515
 // gas legacy: 126728
 // gas legacyOptimized: 123444

test/libsolidity/semanticTests/constructor/bytes_in_constructors_unpacker.sol

@@ -8,7 +8,7 @@ contract Test {
 }
 // ----
 // constructor(): 7, 0x40, 78, "abcdefghijklmnopqrstuvwxyzabcdef", "ghijklmnopqrstuvwxyzabcdefghijkl", "mnopqrstuvwxyz" ->
-// gas irOptimized: 283829
+// gas irOptimized: 284909
 // gas legacy: 309607
 // gas legacyOptimized: 260566
 // m_x() -> 7

test/libsolidity/semanticTests/strings/empty_storage_string.sol

@@ -0,0 +1,100 @@
+contract C {
+
+    string uninitializedString;
+    string emptyString = "";
+    string nonEmptyString = "This is a non empty string";
+    string nonEmptyString2 = "Another string";
+    bytes uninitializedBytes;
+    bytes emptyBytes = "";
+    error EmptyError(string);
+    event EmptyEvent(string);
+
+    function f() public returns (string memory) {
+        return uninitializedString;
+    }
+
+    function g() public returns (string memory, string memory) {
+        return (uninitializedString, emptyString);
+    }
+
+    function h() public returns (string memory, string memory) {
+        return (uninitializedString, nonEmptyString);
+    }
+
+    function i() public returns (string memory, string memory) {
+        return (nonEmptyString, emptyString);
+    }
+
+    function j(string calldata _s) public returns (string memory) {
+        return _s;
+    }
+
+    function k() public returns (string memory) {
+        nonEmptyString2 = "";
+        return nonEmptyString2;
+    }
+
+    function l(string calldata _s) public returns (bytes memory) {
+        return abi.encode(_s);
+    }
+
+    function m() public returns (string memory) {
+        bytes memory b = abi.encode(emptyString);
+        return string(b);
+    }
+
+    function n() public {
+        revert EmptyError(uninitializedString);
+    }
+
+    function o() public {
+        emit EmptyEvent(emptyString);
+    }
+
+    function p() public {
+        emit EmptyEvent("");
+    }
+
+    function q() public returns (bytes memory) {
+        return uninitializedBytes;
+    }
+
+    function r() public returns (bytes memory) {
+        emptyBytes = abi.encode("");
+        return emptyBytes;
+    }
+
+    function s() public returns (bytes memory) {
+        emptyBytes = abi.encode(uninitializedString);
+        return emptyBytes;
+    }
+
+    function set(string calldata _s) public {
+        nonEmptyString = _s;
+    }
+
+    function get() public returns (string memory) {
+        return nonEmptyString;
+    }
+}
+// ====
+// compileViaYul: also
+// ----
+// f() -> 0x20, 0
+// g() -> 0x40, 0x60, 0, 0
+// h() -> 0x40, 0x60, 0, 0x1a, 38178759162904981154304545770567765692299154484752076569098748838215919075328
+// i() -> 0x40, 0x80, 0x1a, 38178759162904981154304545770567765692299154484752076569098748838215919075328, 0
+// j(string): 0x20, 0, "" -> 0x20, 0
+// k() -> 0x20, 0
+// l(string): 0x20, 0, "" -> 0x20, 0x40, 0x20, 0
+// m() -> 0x20, 0x40, 0x20, 0
+// n() -> FAILURE, hex"d3f13430", hex"0000000000000000000000000000000000000000000000000000000000000020", hex"0000000000000000000000000000000000000000000000000000000000000000"
+// o() ->
+// ~ emit EmptyEvent(string): 0x20, 0x00
+// p() ->
+// ~ emit EmptyEvent(string): 0x20, 0x00
+// q() -> 0x20, 0
+// r() -> 0x20, 0x40, 0x20, 0
+// s() -> 0x20, 0x40, 0x20, 0
+// set(string): 0x20, 0, "" ->
+// get() -> 0x20, 0

test/libsolidity/semanticTests/various/address_code.sol

@@ -16,7 +16,7 @@ contract C {
 // compileToEwasm: also
 // ----
 // constructor() ->
-// gas irOptimized: 192317
+// gas irOptimized: 193397
 // gas legacy: 240889
 // gas legacyOptimized: 155314
 // initCode() -> 0x20, 0

test/libsolidity/semanticTests/various/skip_dynamic_types_for_structs.sol

@@ -20,6 +20,6 @@ contract C {
 
 // ----
 // g() -> 2, 6
-// gas irOptimized: 178805
+// gas irOptimized: 178822
 // gas legacy: 180753
 // gas legacyOptimized: 179472