On 01/07/2014 03:37 PM, Laszlo Ersek wrote: > comments below > > On 01/05/14 08:27, Qiao Nuohan wrote: >> functions are used to write page to vmcore. vmcore is written page by page. >> page desc is used to store the information of a page, including a page's >> size, >> offset, compression format, etc. >> >> + uint64_t pfn_start, pfn_end, pfn; >> + unsigned char buf[s->page_size]; > > Whoa, a VLA! :) I believe it's *very* non-idiomatic in the qemu source. > Please consider allocating it dynamically. (Of course others might point > out that I'm wrong.)
Worse, a stack allocation greater than the size of a stack frame. Any time you have a function taking more than a page size of local storage, you risk nasty behavior on some platforms (Windows in particular is notorious for giving you only a single guard page, and if you overflow the stack by more than the guard page, your program is unceremoniously terminated with no message, compared to the usual desirable behavior of getting a SIGSEGV that your program can at least react to in order to diagnose that you had a stack overflow). -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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