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Eliminate MEMORY_OVERFLOW ? #378

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DavePearce opened this issue Oct 5, 2022 · 2 comments · Fixed by #379
Closed

Eliminate MEMORY_OVERFLOW ? #378

DavePearce opened this issue Oct 5, 2022 · 2 comments · Fixed by #379

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@DavePearce
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DavePearce commented Oct 5, 2022 •
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(See also #193, #250 and #265)

An interesting question is whether or not we can now eliminate the idea of a MEMORY_OVERFLOW. My gut feeling, from previous efforts at this, is that we cannot. However, I can't remember the exactly reasoning for this. Similarly, given that we now have gas calculation in place ... well, maybe it could work.

Therefore, this issue is for tracking whether or not this actually can work.
@DavePearce
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DavePearce commented Oct 5, 2022 •
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  • MLOAD
  • MSTORE
  • MSTORE8
  • MSIZE
  • LOGX
  • CALL
  • CALLCODE
  • RETURN
  • DELEGATECALL
  • STATICCALL
  • REVERT
  • CALLDATACOPY
  • CODECOPY
  • EXTCODECOPY
  • CallReturn
  • CreateReturn

@DavePearce
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So, MSIZE and RETURNDATASIZE are problematic. This is because they load the length of memory onto the stack. For these bytecodes, we return the fictional exception MEMORY_OVERFLOW.

DavePearce added a commit that referenced this issue Oct 5, 2022
@DavePearce
Minimise occurence of MEMORY_OVERFLOW #378
c8add30 
The `MEMORY_OVERFLOW` is a ficticious exception create to appease Dafny
in certain circumstances.  In particular, they Yellow Paper places no
restrictions on the bounds of memory.  And yet, there are implied
limits.  In particular, the `MSIZE` bytecode loads the length of memory
onto the stack as a `u256`.  But, the yellow paper says nothing about
what should happen in the event of an overflow.
@DavePearce DavePearce linked a pull request Oct 5, 2022 that will close this issue
Minimise occurence of MEMORY_OVERFLOW #378 #379
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DavePearce added a commit that referenced this issue Oct 5, 2022
@DavePearce
Merge pull request #379 from ConsenSys/378-eliminate-memory_overflow
ccad925 
Minimise occurence of MEMORY_OVERFLOW #378
This was referenced Jan 26, 2023
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Minimise occurence of MEMORY_OVERFLOW #378 Consensys/evm-dafny
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@DavePearce