Hi All, I am trying to compile simple kernel module. It gives following error. Same module compiles succesfully on another 64 bit ubuntu OS.Any idea what different in environment can cause this. Both machine are ubuntu 12.04. On 32 ubuntu bit compilation fails. In file included from /home/aricent/try5/eudy_misc_driver.c:7:0: include/asm-generic/uaccess.h:41:0: warning: "access_ok" redefined [enabled by default] #define access_ok(type, addr, size) __access_ok((unsigned long)(addr),(size)) ^ In file included from /usr/src/linux-headers-3.13.0-43-generic/arch/x86/include/asm/sections.h:5:0, from /usr/src/linux-headers-3.13.0-43-generic/arch/x86/include/asm/hw_irq.h:26, from include/linux/irq.h:368, from /usr/src/linux-headers-3.13.0-43-generic/arch/x86/include/asm/hardirq.h:5, from include/linux/preempt_mask.h:5, from include/linux/sched.h:25, from include/asm-generic/uaccess.h:9, from /home/aricent/try5/eudy_misc_driver.c:7: /usr/src/linux-headers-3.13.0-43-generic/arch/x86/include/asm/uaccess.h:80:0: note: this is the location of the previous definition #define access_ok(type, addr, size) \ In file included from /home/aricent/try5/eudy_misc_driver.c:7:0: include/asm-generic/uaccess.h:337:1: error: static declaration of ‘clear_user’ follows non-static declaration clear_user(void __user *to, unsigned long n) ^ In file included from /usr/src/linux-headers-3.13.0-43-generic/arch/x86/include/asm/sections.h:5:0, from /usr/src/linux-headers-3.13.0-43-generic/arch/x86/include/asm/hw_irq.h:26, from include/linux/irq.h:368, from /usr/src/linux-headers-3.13.0-43-generic/arch/x86/include/asm/hardirq.h:5, from include/linux/preempt_mask.h:5, from include/linux/sched.h:25, from include/asm-generic/uaccess.h:9, from /home/aricent/try5/eudy_misc_driver.c:7: /usr/src/linux-headers-3.13.0-43-generic/arch/x86/include/asm/uaccess.h:525:28: note: previous declaration of ‘clear_user’ was here unsigned long __must_check clear_user(void __user *mem, unsigned long len); Regards Harsh Jain