Dave Korn wrote: > Dave Korn wrote: >> Dave Korn wrote: >> >>> ELF GAS/LD seem happy enough when presented with a ".comm foo,0" >>> directive, >>> but PE does rather literally what you asked, and gives you no data object, >>> leading to i0 in the above being an undefined reference at link time. >> After a bit further digging, it turns out that this is because PE uses the >> same representation for an external symbol as would represent a common of >> size >> 0, so if you define such a common, it magically becomes an undefined external >> symbol instead!
I don't see what the big deal is here: just allocate one byte to a statically- allocated zero-length array. > And testing it on Linux, I see that the linker goes ahead and assigns zero > bytes of the common area to i0, then assigns four bytes of common space to i1 > at the same address, so writing to i0[0] aliases and alters i1. That > certainly sounds like undefined behaviour to me! Sure, but in that case it's clearly the user's fault: they're writing beyond the bounds of an array. Andrew.
