Merge pull request #14931 from mattaereal/develop

Document the possibility of high-level external calls to precompiled contracts

Author: matheusaaguiar

docs/control-structures.rst

@@ -111,22 +111,35 @@ otherwise, the ``value`` option would not be available.
   the ``value`` and ``gas`` settings are lost, only
   ``feed.info{value: 10, gas: 800}()`` performs the function call.
 
-Due to the fact that the EVM considers a call to a non-existing contract to
-always succeed, Solidity uses the ``extcodesize`` opcode to check that
-the contract that is about to be called actually exists (it contains code)
-and causes an exception if it does not. This check is skipped if the return
-data will be decoded after the call and thus the ABI decoder will catch the
-case of a non-existing contract.
+.. warning::
+    Due to the fact that the EVM considers a call to a non-existing contract to
+    always succeed, Solidity uses the ``extcodesize`` opcode to check that
+    the contract that is about to be called actually exists (it contains code)
+    and causes an exception if it does not. This check is skipped if the return
+    data will be decoded after the call and thus the ABI decoder will catch the
+    case of a non-existing contract.
 
-Note that this check is not performed in case of :ref:`low-level calls <address_related>` which
-operate on addresses rather than contract instances.
+    This check is not performed in case of :ref:`low-level calls <address_related>` which
+    operate on addresses rather than contract instances.
 
-.. note::
+.. warning::
     Be careful when using high-level calls to
     :ref:`precompiled contracts <precompiledContracts>`,
     since the compiler considers them non-existing according to the
     above logic even though they execute code and can return data.
 
+.. note::
+    Since the version 0.8.10, the compiler does not check ``extcodesize`` on
+    high-level external calls if return data is expected, because an empty code
+    will be unable to return data, and the ABI decoder will revert.
+    As a consequence, this allows high-level external calls to precompiled
+    contracts, since they can return data despite having no code
+    associated with their addresses.
+
+    Read about :ref:`precompiled contracts <precompiledContracts>` and
+    :ref:`low-level calls <address_related>`
+    for more information.
+
 Function calls also cause exceptions if the called contract itself
 throws an exception or goes out of gas.
 
@@ -901,4 +914,4 @@ in scope in the block that follows.
     out-of-gas situation and not a deliberate error condition:
     The caller always retains at least 1/64th of the gas in a call and thus
     even if the called contract goes out of gas, the caller still
-    has some gas left.
+    has some gas left.