cerc-io/solidity
15
0
Fork 0
mirror of https://github.com/ethereum/solidity synced 2023-10-03 13:03:40 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

Document special case of zero-initialized internal function.

Browse Source
This commit is contained in:
chriseth 2017-01-26 16:28:44 +01:00
parent a98fa41897
commit 7660736aa2
1 changed files with 6 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
docs/control-structures.rst
View File

@ -394,8 +394,13 @@ Currently, Solidity automatically generates a runtime exception in the following
#. If you perform an external function call targeting a contract that contains no code.
#. If your contract receives Ether via a public function without ``payable`` modifier (including the constructor and the fallback function).
#. If your contract receives Ether via a public accessor function.
#. If you call a zero-initialized variable of internal function type.
Internally, Solidity performs an "invalid jump" when a user-provided exception is thrown. In contrast, it performs an invalid (i.e., non-existent) operation if a runtime exception is encountered. In both cases, this causes the EVM to revert all changes made to the state. The reason for this is that there is no safe way to continue execution, because an expected effect did not occur. Because we want to retain the atomicity of transactions, the safest thing to do is to revert all changes and make the whole transaction (or at least call) without effect.
Internally, Solidity performs an "invalid jump" when a user-provided exception is thrown. In contrast, it performs an invalid operation
(code ``0xfe``) if a runtime exception is encountered. In both cases, this causes
the EVM to revert all changes made to the state. The reason for this is that there is no safe way to continue execution, because an expected effect
did not occur. Because we want to retain the atomicity of transactions, the safest thing to do is to revert all changes and make the whole transaction
(or at least call) without effect.
.. index:: ! assembly, ! asm, ! evmasm