Why Thread.Start can throw OutOfMemoryException

Question

This question is related with my previous question Thread overhead

Since Thread.Start doesn't claim memory for the thread to run, why it can throw OutOfMemoryException?

Answer 1

Here's part of the source code for starting up a managed thread in the CLR:

CExecutionEngine::SetupTLSForThread(pThread);
if (!pThread->InitThread(fInternal) ||
    !pThread->PrepareApartmentAndContext())
    ThrowOutOfMemory();
if (UnsafeTlsSetValue(gThreadTLSIndex, (VOID*)this) == 0)
{
    ThrowOutOfMemory();
}
if (UnsafeTlsSetValue(GetAppDomainTLSIndex(), (VOID*)m_pDomain) == 0)
{
    ThrowOutOfMemory();
}

Sure looks like it can throw out of memory in a number of situations; if the thread cannot be initialized, if the apartment or context cannot be prepared, or if the thread local storage cannot be allocated, then "out of memory" is thrown.

In my opinion this is a bad idea; I would prefer "out of memory" to be reserved for the situation of "I tried to allocate a new block of virtual memory and I couldn't find a block of the needed size." Throwing out of memory for things like there being no TLS slots available or thread initialization failing is just confusing.