On 02/23/2017 06:33 AM, Peter Maydell wrote: > What's the right way to use libfdt's fdt_setprop to set a property > to have an empty value? At the moment in QEMU we tend to use > fdt_setprop(fdt, nodeoffset, "propertyname", NULL, 0); > > and git grep 'fdt_setprop.*NULL' produces examples of this usage in > PPC and ARM fdt creation code. > > However the fdt_setprop() documentation doesn't document that a NULL > value pointer is OK if the length is 0, and indeed the implementation > unconditionally calls memcpy(prop->data, val, len), which is > undefined behaviour, and warned about by clang sanitizers if you > build libfdt with them: > dtc/libfdt/fdt_rw.c:288:21: runtime error: null pointer passed > as argument 2, which is declared to never be null > > So what's the best thing to do here? I can't offhand think of a > non-ugly/non-confusing way to pass a valid pointer here...
Does fdt_setprop(fdt, nodeoffset, "propertyname", "", 0) do the right thing? -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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