a cglobal intrinsic for C library global variables.

[stevengj]

Currently, you can only access global variables by a combination of dlsym and dlopen: convert(Ptr{T}, dlsym(dlopen("libname"), "varname")). Not only is this ugly, but it will also make things difficult for future static compilation (where we would like to directly link any needed shared libraries with ld, rather than requiring them to be dlopened at runtime).

I'd like to suggest a cglobal(symbol, T=Void) intrinsic, returning a Ptr{T}, that mirrors ccall(symbol, ...). That is, the symbol argument could be a symbol, a (symbol,library) pair, or a pointer returned by dlsym (although in that case cglobal wouldn't do much, just a typecast).

(See #961 for some pre-history of this problem.)

[JeffBezanson]

See also #1815

[stevengj]

Ah, seems to be a duplicate issue.