Move msg.gas to global function gasleft(). Closes #2971.

docs/contracts.rst

@@ -402,7 +402,7 @@ State variables can be declared as ``constant``. In this case, they have to be
 assigned from an expression which is a constant at compile time. Any expression
 that accesses storage, blockchain data (e.g. ``now``, ``this.balance`` or
 ``block.number``) or
-execution data (``msg.gas``) or make calls to external contracts are disallowed. Expressions
+execution data (``msg.value``) or make calls to external contracts are disallowed. Expressions
 that might have a side-effect on memory allocation are allowed, but those that
 might have a side-effect on other memory objects are not. The built-in functions
 ``keccak256``, ``sha256``, ``ripemd160``, ``ecrecover``, ``addmod`` and ``mulmod``

docs/miscellaneous.rst

@@ -315,8 +315,9 @@ Global Variables
 - ``block.gaslimit`` (``uint``): current block gaslimit
 - ``block.number`` (``uint``): current block number
 - ``block.timestamp`` (``uint``): current block timestamp
+- ``gasleft() returns (uint256)``: remaining gas
 - ``msg.data`` (``bytes``): complete calldata
-- ``msg.gas`` (``uint``): remaining gas
+- ``msg.gas`` (``uint``): remaining gas - deprecated in version 0.4.21 and to be replaced by ``gasleft()``
 - ``msg.sender`` (``address``): sender of the message (current call)
 - ``msg.value`` (``uint``): number of wei sent with the message
 - ``now`` (``uint``): current block timestamp (alias for ``block.timestamp``)

docs/units-and-global-variables.rst

@@ -58,8 +58,9 @@ Block and Transaction Properties
 - ``block.gaslimit`` (``uint``): current block gaslimit
 - ``block.number`` (``uint``): current block number
 - ``block.timestamp`` (``uint``): current block timestamp as seconds since unix epoch
+- ``gasleft() returns (uint256)``: remaining gas
 - ``msg.data`` (``bytes``): complete calldata
-- ``msg.gas`` (``uint``): remaining gas
+- ``msg.gas`` (``uint``): remaining gas - deprecated in version 0.4.21 and to be replaced by ``gasleft()``
 - ``msg.sender`` (``address``): sender of the message (current call)
 - ``msg.sig`` (``bytes4``): first four bytes of the calldata (i.e. function identifier)
 - ``msg.value`` (``uint``): number of wei sent with the message