gcc can check printf like variable arguments. These patches tell gcc to do so for several functions.
[PATCH 1/4] blockdev.h: Add GCC attribute (check format arguments) [PATCH 2/4] darwin-user: Add GCC attribute (check format arguments) [PATCH 3/4] qemu-char.h: Add GCC attribute (check format arguments) [PATCH 4/4] slirp.h: Add GCC attribute (check format arguments)
