add Best Practice check for vkAllocateDescriptorSets returning VK_SUCCESS when it should've VK_OUT_OF_POOL_MEMORY

[AlexRouSg]

Too often do people going between GPU vendors, especially the newer coders, get tripped up by vkAllocateDescriptorSets returning VK_SUCCESS even tho the pool sizes was too small to allocate the set.

I would like to suggest this get a Best Practice check tho none of the current options seem too suited, maybe a new "PC Portability Best Practice"? This check should effectively be a ref counter incrementing on vkAllocateDescriptorSets and decrementing on vkFreeDescriptorSets or vkResetDescriptorPool, and then if vkAllocateDescriptorSets succeeds but the ref counter overflows the sizes on creation does it emit a warning.

[spencer-lunarg]

I am all for this in Best Practices, but the issue is how to decide when to report it

ref counter overflows the sizes

what is the overflow limit?

There is a BestPractices-Arm-vkAllocateDescriptorSets-suboptimal-reuse check that might be similar

[AlexRouSg]

So the general idea I had is hook on to vkCreateDescriptorPool and have like a class containing

class DescriptorPoolRefCounter {
class Counter {
    int limit;
    int counter;
}
int maxSets;
std::unordered_map<VkDescriptorType, Counter> descriptorTypes;
}

amd then

vkCreateDescriptorPool(... VkDescriptorPoolCreateInfo info) {
    DescriptorPoolRefCounter counter;
    counter.maxSets = info.maxSets
    for (int i = 0; i < info.poolSizeCount; i++) {
        counter.descriptorTypes[info.pPoolSizes[i].type] = DescriptorPoolRefCounter::Counter(info.pPoolSizes[i].descriptorCount, 0);
    }
}

Then every call to vkAllocateDescriptorSets we lookup what are the descriptor counts in the set layout and increment the counters for the respective VkDescriptorType, call the actual vkAllocateDescriptorSets, if it returns VK_SUCCESS we loop over all the counters and check counter > limit if true then emit the warning

EDIT:
I forgot about

If multiple VkDescriptorPoolSize structures containing the same descriptor type appear in the pPoolSizes array then the pool will be created with enough storage for the total number of descriptors of each type.

So the for loop in vkCreateDescriptorPool needs to do an addition rather than an assignment