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| -rw-r--r-- | docs/contracts.rst | 23 |
1 files changed, 16 insertions, 7 deletions
diff --git a/docs/contracts.rst b/docs/contracts.rst index c1c51e56..68c7bea3 100644 --- a/docs/contracts.rst +++ b/docs/contracts.rst @@ -569,6 +569,20 @@ In addition to the list of state modifying statements explained above, the follo } } +Pure functions are able to use the `revert()` and `require()` functions to revert +potential state changes when an :ref:`error occurs <assert-and-require>`. + +Reverting a state change is not considered a "state modification", as only changes to the +state made previously in code that did not have the ``view`` or ``pure`` restriction +are reverted and that code has the option to catch the ``revert`` and not pass it on. + +This behaviour is also in line with the ``STATICCALL`` opcode. + +.. warning:: + It is not possible to prevent functions from reading the state at the level + of the EVM, it is only possible to prevent them from writing to the state + (i.e. only ``view`` can be enforced at the EVM level, ``pure`` can not). + .. note:: Prior to version 0.5.0, the compiler did not use the ``STATICCALL`` opcode for ``pure`` functions. @@ -577,13 +591,8 @@ In addition to the list of state modifying statements explained above, the follo By using ``STATICCALL`` for ``pure`` functions, modifications to the state are prevented on the level of the EVM. -.. warning:: - It is not possible to prevent functions from reading the state at the level - of the EVM, it is only possible to prevent them from writing to the state - (i.e. only ``view`` can be enforced at the EVM level, ``pure`` can not). - -.. warning:: - Before version 0.4.17 the compiler did not enforce that ``pure`` is not reading the state. +.. note:: + Prior to version 0.4.17 the compiler did not enforce that ``pure`` is not reading the state. It is a compile-time type check, which can be circumvented doing invalid explicit conversions between contract types, because the compiler can verify that the type of the contract does not do state-changing operations, but it cannot check that the contract that will be called |