Should I compile with /MD or /MT?
In Visual Studio, there's the compile flags /MD and /MT which let you choose which kind of C runtime library you want.
I understand the difference in implementation, but I'm still not sure which one to use. What are the pros/cons?
One advantage to /MD that I've heard, is that this allows someone to update the runtime, (like maybe patch a security problem) and my app will benefit from this update. Although to me, this almost seems like a non-feature: I don't want people changing my runtime without allowing me to test against the new version!
Some things I am curious about:
- How would this affect build times? (presumably /MT is a little slower?)
- What are the other implications?
- Which one do most people use?
Answer
By dynamically linking with /MD,
- you are exposed to system updates (for good or ill),
- your executable can be smaller (since it doesn't have the library embedded in it), and
- I believe that at very least the code segment of a DLL is shared amongst all processes that are actively using it (reducing the total amount of RAM consumed).
I've also found that in practice, when working with statically-linked 3rd-party binary-only libraries that have been built with different runtime options, /MT in the main application tends to cause conflicts much more often than /MD (because you'll run into trouble if the C runtime is statically-linked multiple times, especially if they are different versions).