So I spent some time looking at this today and trying to get this to work with VLAs in SunStudio. Doing research, I ran across this:
"C99 VLAs were discussed in the C++ Committee for possible inclusion in the next standard. The unanimous view was that they did not have nice properties (the word "suck" was bandied about), and that std::vector or other containers were a superior solution in C++ programming."
Thus, while _func_ works with CC -features=extensions, it doesn't appear that Sun Studio supports all of the C99 features in their C++ compiler. This makes me wonder if using _func_ was the right thing to do now.
They also have an interesting discussion about alloca vs. malloc.