Now ensuring that enum index is positive #34
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jmjaffe37
changed the title
swesonga
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Sep 4, 2025
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| int MemoryManager::add_pool(MemoryPool* pool) { | ||
| int index = _num_pools; | ||
| assert(index < MemoryManager::max_num_pools, "_num_pools exceeds the max"); |
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We need an assert on the lower bound as well
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@swesonga what should the lower bound be? Should it be 1? Here is an example line that I could add:
assert(index >= 1, "_num_pools must be at least 1");
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When accessing array _pools with index index, the upper bound of an enum is used to check the upper bound of the array, but the lower bound is not checked. This simple PR fixes this issue
Code using enumerated types as indexes into arrays will often check for an upper bound to ensure the index is not out of range. By default an enum variable is signed, and therefore it is important to ensure that it cannot take on a negative value. When the enum is subsequently used to index an array, or worse still an array of function pointers, then a negative enum value would lead to potentially arbitrary memory being read, used and/or executed.