Maybe your compiler version is different from us. Mine is 4.9.2（debian）as same as daveti's. 发自 网易邮箱大师 在2016年03月07日 10:51，Adam Lee 写道: On Sat, Mar 05, 2016 at 11:37:21AM +0800, 张云 wrote:
On Mar 4, 2016, at 11:59 PM, Dave Tian <dave.jing.tian@gmail.com> wrote:
This ‘P’ is used to make gcc happy and work. Without ‘P’, this inline would be interpreted as: leal $-512(%esp), %eax With ‘P’, this inline is the thing we really want: leal -512(%esp), %eax
Eventually, my gcc 4.9.2 does not compile with ‘P’ is missing. I am not sure if this is still the case for newer gcc (5/6). But you get the point.
-daveti
Thank you for your detailed answer !
By the way， If someone have the problems alike, I suggest them to write some inline assembly and check the compiler’s assembly output.
Didn't get different outputs here, do you have updates? -- Adam Lee http://adam8157.info _______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies