On 10/10/2012 02:34 PM, Eric Blake wrote: > On 10/10/2012 12:29 PM, Jeff Cody wrote: > >>> That's a LOT of stack space, which risks stack overflow, will mostly be >>> unused, and still doesn't work if you have super-deep hierarchies larger >>> than PATH_MAX. Would you be better off using realpath(,NULL) for its >>> allocating semantics, and then free()ing the results? >>> >> >> That is the main reason I changed it from being a recursive function, to >> an iterative one. >> >> Do we know that realpath(,NULL) behaves the same on all platforms? > > Gnulib lists the following platforms as mis-handling NULL: > Mac OS X 10.5, FreeBSD 6.4, OpenBSD 4.4, Solaris 10. > >> >> We had a thread back in April that touched on the use of realpath, and >> concerns were raised then that realpath(,NULL) was not necessarily safe >> across all OSes: >> >> https://lists.gnu.org/archive/html/qemu-devel/2012-04/msg01417.html > > In fact, that message points out an even more insidious portability bug > in your algorithm: on Solaris 10, realpath("relative", buffer) leaves > buffer containing "relative" rather than an absolute name, but your > algorithm depends on matching absolute names. I don't know if we port > qemu to Solaris 10, but it's worth considering my question back in that > thread - does glib provide us a more portable function for converting a > relative name into a canonical path that is guaranteed to work everywhere? >
We are already relying on realpath() in block.c. So rather than making this patch series much more complicated for a minor fix, I think that if there are concerns about realpath() on other OSes such as Solaris 10, then those concerns should be addressed in a separate patch series. >> >> That said, if there is concern over the stack usage, to be safe I can >> manually g_malloc() each array. > > g_malloc() would solve the stack size concern, but not the Solaris 10 > relative name bug. >
