[fpc-devel] Why/how does the compiler have a non-trivial numberof memory leaks after over two decades of development?

[J. Gareth Moreton]

 Well, I'm only a volunteer developer, but I'm all for making the compiler
more efficient and stable.  I tend to take the approach of iterative
improvement anyway... start with something quick and dirty (if you can't
easily plan it out perfectly from the start), and slowly improve it over
time.

 Gareth aka. Kit

 On Thu 02/08/18 19:39 , Ben Grasset operator97 at gmail.com sent:
 I'm somewhat surprised to see all the mentions of try-finally in 
 response to this. 

 The issues I found and described here are all clearly just simple cases 
 of variables being created and then never freed. Part of what likely 
 leads to this is that the compiler relies in many places on checking 
 whether or not things are currently nil, and heavily reuses global 
 variables for this purpose. 

 So it's quite likely in my opinion that there's places where things are 
 in fact being set to nil without actually being freed first, which has 
 the potential to go beyond basic leaks and actually lead to memory 
 corruption problems than could cause real compiler bugs (and might 
 already be doing so.) 

 I really don't think that try/finally is particularly relevant for this 
 kind of thing, nor would it be good for compiler performance. I do think 
 however that it's quite viable to get some kind of system in place in 
 the compiler codebase (hidden behind one of the debug-related ifdefs so 
 that it never affects normal compiler builds at all) that would allow 
 for much easier soundness-checking while working on the compiler than 
 HeapTrace can provide on its own. 

 I've been trying out a few different approaches in the last few days, 
 and if there's any interest in something like this from the compiler 
 team I might post here for feedback once I get something more concrete 
 worked out. 

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