[Certora Audit] G-10. ++i costs less gas compared to i++ or i+=1 (#897)

This pull request includes several changes to increment and decrement
operations in various Solidity contract files. The primary goal is to
decrease gas usage.

Pre-increments and pre-decrements are cheaper.
For a uint256 i variable, the following is true with the Optimizer
enabled at 10k:
Increment:
- i += 1 is the most expensive form
- i++ costs 6 gas less than i += 1
- ++i costs 5 gas less than i++ (11 gas less than i += 1)

Decrement:
- i -= 1 is the most expensive form
- i-- costs 11 gas less than i -= 1
- --i costs 5 gas less than i-- (16 gas less than i -= 1)

Changes to increment and decrement operations:

*
[`contracts/Safe.sol`](diffhunk://#diff-587b494ea631bb6b7adf4fc3e1a2e6a277a385ff16e1163b26e39de24e9483deL296-R296):
Updated the for loop to use the prefix increment operator in the `Safe`
contract.
*
[`contracts/base/ModuleManager.sol`](diffhunk://#diff-82762908b9416ddadffb149ee4d25f328078fc27f938d454d8a207aad1ec3839L215-R215):
Changed the increment operation to use the prefix increment operator in
the `ModuleManager` contract.
*
[`contracts/base/OwnerManager.sol`](diffhunk://#diff-795fb06764b4c2d991707584a31509badf0b036c9401bfbcb82d6bc9fdebab82L38-R38):
Multiple updates to use prefix increment and decrement operators in the
`OwnerManager` contract.
[[1]](diffhunk://#diff-795fb06764b4c2d991707584a31509badf0b036c9401bfbcb82d6bc9fdebab82L38-R38)
[[2]](diffhunk://#diff-795fb06764b4c2d991707584a31509badf0b036c9401bfbcb82d6bc9fdebab82L63-R63)
[[3]](diffhunk://#diff-795fb06764b4c2d991707584a31509badf0b036c9401bfbcb82d6bc9fdebab82L80-R80)
[[4]](diffhunk://#diff-795fb06764b4c2d991707584a31509badf0b036c9401bfbcb82d6bc9fdebab82L142-R142)
*
[`contracts/common/StorageAccessible.sol`](diffhunk://#diff-a7dd65d90b0567bb9ba14ecd4ff414529a934cd3752ccf309800fad93fba354eL19-R19):
Modified the for loop to use the prefix increment operator in the
`StorageAccessible` contract.
*
[`contracts/handler/extensible/ERC165Handler.sol`](diffhunk://#diff-aa0838f20fd3f37b00dc661645b4641500e68762b9b624addb99465fcc65a3e0L56-R56):
Updated for loops to use the prefix increment operator in the
`ERC165Handler` contract.
[[1]](diffhunk://#diff-aa0838f20fd3f37b00dc661645b4641500e68762b9b624addb99465fcc65a3e0L56-R56)
[[2]](diffhunk://#diff-aa0838f20fd3f37b00dc661645b4641500e68762b9b624addb99465fcc65a3e0L78-R78)
*
[`contracts/libraries/SafeToL2Migration.sol`](diffhunk://#diff-925588b812f729cc164d14a48e571ce813e2f0ae6f5c5420fc0382c767287fd0L188-R188):
Changed the increment operation to use the prefix increment operator in
the `SafeToL2Migration` contract.

contracts/Safe.sol

@@ -297,7 +297,7 @@ contract Safe is
         // we can safely ignore this malleability.
         bytes32 s;
         uint256 i;
-        for (i = 0; i < requiredSignatures; i++) {
+        for (i = 0; i < requiredSignatures; ++i) {
             (v, r, s) = signatureSplit(signatures, i);
             if (v == 0) {
                 // If v is 0 then it is a contract signature

contracts/base/ModuleManager.sol

@@ -212,7 +212,7 @@ abstract contract ModuleManager is SelfAuthorized, Executor, IModuleManager {
         while (next != address(0) && next != SENTINEL_MODULES && moduleCount < pageSize) {
             array[moduleCount] = next;
             next = modules[next];
-            moduleCount++;
+            ++moduleCount;
         }
 
         /**

contracts/base/OwnerManager.sol

@@ -36,7 +36,7 @@ abstract contract OwnerManager is SelfAuthorized, IOwnerManager {
         // Initializing Safe owners.
         address currentOwner = SENTINEL_OWNERS;
         uint256 ownersLength = _owners.length;
-        for (uint256 i = 0; i < ownersLength; i++) {
+        for (uint256 i = 0; i < ownersLength; ++i) {
             // Owner address cannot be null.
             address owner = _owners[i];
             if (owner == address(0) || owner == SENTINEL_OWNERS || owner == address(this) || currentOwner == owner)
@@ -61,7 +61,7 @@ abstract contract OwnerManager is SelfAuthorized, IOwnerManager {
         if (owners[owner] != address(0)) revertWithError("GS204");
         owners[owner] = owners[SENTINEL_OWNERS];
         owners[SENTINEL_OWNERS] = owner;
-        ownerCount++;
+        ++ownerCount;
         emit AddedOwner(owner);
         // Change threshold if threshold was changed.
         if (threshold != _threshold) changeThreshold(_threshold);
@@ -140,7 +140,7 @@ abstract contract OwnerManager is SelfAuthorized, IOwnerManager {
         while (currentOwner != SENTINEL_OWNERS) {
             array[index] = currentOwner;
             currentOwner = owners[currentOwner];
-            index++;
+            ++index;
         }
         return array;
     }

contracts/common/StorageAccessible.sol

@@ -16,7 +16,7 @@ abstract contract StorageAccessible {
      */
     function getStorageAt(uint256 offset, uint256 length) public view returns (bytes memory) {
         bytes memory result = new bytes(length * 32);
-        for (uint256 index = 0; index < length; index++) {
+        for (uint256 index = 0; index < length; ++index) {
             /* solhint-disable no-inline-assembly */
             /// @solidity memory-safe-assembly
             assembly {

contracts/handler/extensible/ERC165Handler.sol

@@ -56,7 +56,7 @@ abstract contract ERC165Handler is ExtensibleBase, IERC165Handler {
         ISafe safe = ISafe(payable(_msgSender()));
         bytes4 interfaceId;
         uint256 len = handlerWithSelectors.length;
-        for (uint256 i = 0; i < len; i++) {
+        for (uint256 i = 0; i < len; ++i) {
             (bool isStatic, bytes4 selector, address handlerAddress) = MarshalLib.decodeWithSelector(handlerWithSelectors[i]);
             _setSafeMethod(safe, selector, MarshalLib.encode(isStatic, handlerAddress));
             if (i > 0) {
@@ -79,7 +79,7 @@ abstract contract ERC165Handler is ExtensibleBase, IERC165Handler {
         ISafe safe = ISafe(payable(_msgSender()));
         bytes4 interfaceId;
         uint256 len = selectors.length;
-        for (uint256 i = 0; i < len; i++) {
+        for (uint256 i = 0; i < len; ++i) {
             _setSafeMethod(safe, selectors[i], bytes32(0));
             if (i > 0) {
                 interfaceId ^= selectors[i];

contracts/libraries/SafeToL2Migration.sol

@@ -185,7 +185,7 @@ contract SafeToL2Migration is SafeStorage {
         while (currentOwner != sentinelOwners) {
             array[index] = currentOwner;
             currentOwner = owners[currentOwner];
-            index++;
+            ++index;
         }
         return array;
     }