fix shifts possibly larger than type in major() macro

in theory this should not be an issue, since major() should only be
applied to type dev_t, which is 64-bit. however, it appears some
applications are not using dev_t but a smaller integer type (which
works on Linux because the kernel's dev_t is really only 32-bit). to
avoid the undefined behavior, do it as two shifts.

diff --git a/include/sys/sysmacros.h b/include/sys/sysmacros.h
index d6c6aef631f207b7507eb6fbeab5d454fdf13b79..07a3ef183cb63eaa3b4bd62671a8a0e010ca89da 100644 (file)
--- a/include/sys/sysmacros.h
+++ b/include/sys/sysmacros.h
@@ -2,7 +2,7 @@
 #define _SYS_SYSMACROS_H
 
 #define major(x) \
-       ((unsigned)( (((x)>>32) & 0xfffff000) | (((x)>>8) & 0x00000fff) ))
+       ((unsigned)( (((x)>>31>>1) & 0xfffff000) | (((x)>>8) & 0x00000fff) ))
 #define minor(x) \
        ((unsigned)( (((x)>>12) & 0xffffff00) | ((x) & 0x000000ff) ))