Fix unset internal function pointer retrieval from packed storage slot with a subsequent non-zero variable - #16776
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| if (type->category() == Type::Category::UserDefinedValueType) | ||
| type = type->encodingType(); | ||
| bool cleaned = false; | ||
| // shift bytes to the right positioning the function pointer at the start of the slot |
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I am a bit confused about this comment. retrieveValue is a general method, no? It deals with all types, not only function pointers.
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Yes, true. I guess I got to much focused on function pointers at the time 😅
I will change it to state variable, ok?
| // shift bytes to the right positioning the function pointer at the start of the slot | ||
| m_context | ||
| << Instruction::SWAP1 << s_loadInstruction << Instruction::SWAP1 | ||
| << u256(0x100) << Instruction::EXP << Instruction::SWAP1 << Instruction::DIV; |
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Side note: If this is supposed to do shift, it does not need to use EXP instruction for that.
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DIV does the right shifting. I am trying to remember exactly, but I think that EXP is just telling by how much you shift.
I will confirm this.
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Also, just for clarity, I think this uses DIV (and other places MUL) because shift opcodes were introduced in later EVM versions.
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I had "decoded" this before, but it was used with MUL in another place.
The variable offset is given in bytes, EXP 0x100, offset computes the amount of bits to shift when using DIV.
256^offset = (2^8)^offset = 2^8 * offset.
When the bytes of the slot are divided by this value, it is equivalent to shifting it 8 * offset bits to the right.
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Fix #16775.