On 3/1/20 8:35 AM, Julio Faracco wrote: > When HAX is enabled (--enable-hax), GCC 9.2.1 reports issues with > snprintf(). This commit is checking if snprintf returns an error. This > is a simple way to avoid this warnings. > > For more details, one example of warning: > CC i386-softmmu/target/i386/hax-posix.o > qemu/target/i386/hax-posix.c: In function ‘hax_host_open_vm’: > qemu/target/i386/hax-posix.c:124:56: error: ‘%02d’ directive output may be > truncated writing between 2 and 11 bytes into a region of size 3 > [-Werror=format-truncation=] > 124 | snprintf(name, sizeof HAX_VM_DEVFS, "/dev/hax_vm/vm%02d", vm_id); > | ^~~~ > qemu/target/i386/hax-posix.c:124:41: note: directive argument in the range > [-2147483648, 64]
The code bounds vm_id from the top (64) but not the bottom. The compiler has (correctly) determined that negative values will overflow your buffer. I suggest either an assert vs negative values as a local change, or to change the type of vm_id (universally, if possible) to an unsigned type. r~
