I was wondering if anyone could help me investigate a bug I am seeing
in the GCC garbage collector. This bug (which may or may not be PR
89179) is causing a segfault in GCC, but when I try to create a
preprocessed source file, the bug doesn't trigger. The problem is with
the garbage collector trying to mark some memory that has already been
freed. I have tracked down the initial allocation to:
symbol_table::allocate_cgraph_symbol
It has:
node = ggc_cleared_alloc<cgraph_node> ();
to allocate a cgraph node. With the GGC debugging on I see this
allocated:
Allocating object, requested size=360, actual=360 at 0xffff7029c210 on
0x41b148c0
then freed:
Freeing object, actual size=360, at 0xffff7029c210 on 0x41b148c0
And then later, while the garbage collector is marking nodes, I see:
Marking 0xffff7029c210
The garbage collector shouldn't be marking this node if has already
been freed.
So I guess my main question is how do I figure out how the garbage
collector got to this memory location? I am guessing some GTY pointer
is still pointing to it and hadn't got nulled out when the memory was
freed. Does that seem like the most likely cause?
I am not sure why I am only running into this with one particular
application on my Aarch64 platform. I am building it with -fopenmp,
which could have something to do with it (though there are no simd functions in
the application). The application is not that large as C++ programs go.
Steve Ellcey
[email protected]
