[MLton] Re: cygwoes

[Matthew Fluet]

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> I did a little more investigating of the Virtual{Alloc,Free} problems over 
> the weekend, and I'm mostly convinced that (at least through Cygwin), they 
> are not working as advertised by the API.  I've got more info at home that 
> I'll try to post this evening.

Here is a quick little program that replicates the relevant parts of gc.c 
and platform/windows.c that call VirtualAlloc with a non-NULL starting 
address.  When I run it under Cygwin, I get:

start = 0x60000000  size = 8192
Error: VirtualFree failed with error 87: The parameter is incorrect.
start = 0x60000000  size = 16384
Error: VirtualFree failed with error 87: The parameter is incorrect.
start = 0x18000000  size = 32768
Error: VirtualFree failed with error 487: Attempt to access invalid address.
start = 0x18000000  size = 65536
Error: VirtualFree failed with error 487: Attempt to access invalid address.
start = 0x18000000  size = 131072
Error: VirtualFree failed with error 487: Attempt to access invalid address.
start = 0x18000000  size = 262144
Error: VirtualFree failed with error 487: Attempt to access invalid address.
start = 0x18000000  size = 524288
Error: VirtualFree failed with error 487: Attempt to access invalid address.
start = 0x18000000  size = 1048576
Error: VirtualFree failed with error 487: Attempt to access invalid address.
start = 0x18000000  size = 2097152
Error: VirtualFree failed with error 487: Attempt to access invalid address.
start = 0x18000000  size = 4194304
Error: VirtualFree failed with error 487: Attempt to access invalid address.
start = 0x10000000  size = 8388608
Error: VirtualFree failed with error 487: Attempt to access invalid address.
start = 0x10000000  size = 16777216
Error: VirtualFree failed with error 487: Attempt to access invalid address.
start = 0x10000000  size = 33554432
Error: VirtualFree failed with error 487: Attempt to access invalid address.
start = 0x10000000  size = 67108864
Error: VirtualFree failed with error 487: Attempt to access invalid address.
start = 0x10000000  size = 134217728
Error: VirtualFree failed with error 487: Attempt to access invalid address.
start = 0x08000000  size = 268435456
Error: VirtualFree failed with error 487: Attempt to access invalid address.

Yet, all the program does is immediately VirtualFree the memory returned 
by VirtualAlloc.  As best I can tell, this behavior is not consistent with 
the API.  If any of the more Windows savvy programmers can see why this is 
the appropriate behavior, we'd like to know.  I'm also interested if 
anyone could try to compile and run the program as a native Windows 
application (i.e., not through Cygwin).  I'm curious to see if the same 
behavior is also observed there.

If I change the call to VirtualAlloc to take NULL as the starting address, 
I get:

start = 0x18b70000  size = 8192
start = 0x18b70000  size = 16384
start = 0x18b70000  size = 32768
start = 0x18b70000  size = 65536
start = 0x18b70000  size = 131072
start = 0x18b70000  size = 262144
start = 0x18b70000  size = 524288
start = 0x18b70000  size = 1048576
start = 0x18b70000  size = 2097152
start = 0x18b70000  size = 4194304
start = 0x18b70000  size = 8388608
start = 0x18b70000  size = 16777216
start = 0x18b70000  size = 33554432
start = 0x18b70000  size = 67108864
start = 0x18b70000  size = 134217728
start = 0x18b70000  size = 268435456
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