Potential dangling string pointer to stack in syscall_aux

_From [rnk@google.com](https://code.google.com/u/rnk@google.com/) on May 15, 2012 11:43:21_

We store packed_callstack_t's in our error_table, and we just copy the syscall_aux string pointer when we clone. This assumes that these are all pointers to string literals, which is the case most of the time. However, there are a few instances in our code base where we violate this invariant.

On syscall_linux.c:699, we have a stack temporary idmsg[32] that we snprintf to and use that. When I looked, there was one on Windows as well, but I'd have to search to find it.

These typically don't manifest in any way, because we don't ever try to print or symbolize stacks stored in our error_table. However, they are considered when doing error de-duplication since the syscall_aux pointer value is used in the hash (I think?) and in the equality comparison, where it is likely to always differ.

_Original issue: http://code.google.com/p/drmemory/issues/detail?id=888_