[PATCH] Implement variable-sized alloca instrumentation (take 2).

[Kostya Serebryany]

> Right, that's why we originally proposed lists. Wouldn't this be much simpler?


There is nothing simpler than a non-resizable array :) 
I still urge you to find a solution w/o lists, I think it's possible. 
If nothing good shows up, ok, let's do lists, but in the asan-runtime (as opposed to compiler module)

try to minimize the amount of compiler changes. something like

1. all dynamic alloca() are replaced with __asan_dynamic_alloca which will use fake stack in use-after-return mode and real stack (with redzones) in base mode.
2. at all RET instructions __asan_release_dynamic_allocas is called, but in presence of exceptions/longjmp there is a backup recovery mechanism.

> 

> 

> > So, maybe we simply use the existing fake stack (in use-after-return mode, or maybe even by default?) to simulate dynamic alloca?

> 

> 

> I'd oppose to that - fake stacks pose unacceptable RAM overheads for mobile devices.


Fair enough.


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