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10 = 666; considered legal #72

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tommythorn opened this issue Sep 5, 2022 · 0 comments
Open

10 = 666; considered legal #72

tommythorn opened this issue Sep 5, 2022 · 0 comments

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@tommythorn
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I cut my teeth on Small-C eons ago and c4 is an absolute delight and very clever. However, I did think the lvalue trick looked too fragile and indeed, if you generate just the right constant, like 9 or 10, you can trick it.

int main(int argc, char **argv) {
    10 = 666;
}

This compiles and will lead to stack corruption.

Definitely not hard to fix and probably not worthwhile.
tommythorn added a commit to tommythorn/c4 that referenced this issue Sep 10, 2022
@tommythorn
Fix rswier#72: don't mistake immediates for opcodes
c130b6f 
When checking if the last generated instruction was a load, we have to
protected against all the other things that can look like a load.
Since we only ever care about the most recently generated load and we
always overwrite with another opcode it suffice to trace the address
of the most recently generated load.
tommythorn added a commit to tommythorn/c4 that referenced this issue Sep 14, 2023
@tommythorn
Fix for rswier#72 introduced a different bug; now c4 c4.c hello.c works
461d260
tommythorn added a commit to tommythorn/c4 that referenced this issue Sep 15, 2023
@tommythorn
Fix rswier#72: don't mistake immediates for opcodes
c5106bd 
When checking if the last generated instruction was a load, we have to
protected against all the other things that can look like a load.
Since we only ever care about the most recently generated load and we
always overwrite with another opcode it suffice to trace the address
of the most recently generated load.
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@tommythorn