On 5/3/2011 1:32 AM, Walter Bright wrote:
On 5/1/2011 12:44 PM, David Simcha wrote:
Update: The segfaults on Linux64 are also being caused by the low
order bit corruption bug. Whenever I look at the chain of pointer
dereferences in GDB by viewing the registers and disassembly on
crash, the segfault is always caused by dereferencing a pointer to
some memory address that's clearly illegal. (On x64 user mode
addresses can't have their high order bits set, and the addresses
being dereferenced often do. See
http://en.wikipedia.org/wiki/X64#Virtual_address_space_details .)
This wild pointer is obtained by dereferencing another pointer whose
low order bits are always equal to TaskStatus.done. For example, if
TaskStatus.done == 2, the pointer might be something like 0x0000ABCD
EF123402. If TaskStatus.done == 1, it will be something like
0x0000ABCD EF123401.
Add asserts on that pointer value going out of range, and keep working
backwards until the point where the value goes wrong is discovered.
Been trying to do that, but I think there are multiple places where this
is happening and the asserts are affecting codegen or timings just
enough to prevent some. Similarly, putting a try/catch block in some
seemingly unrelated place prevents certain manifestations on Windows.
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