Le 28/05/2018 à 16:37, Segher Boessenkool a écrit :
On Mon, May 28, 2018 at 02:17:49PM +0000, Christophe Leroy wrote:
Latest GCC version emit many warnings similar to the following one.
You didn't actually show an example?
Yes I forgot:
In file included from arch/powerpc/kernel/syscalls.c:24:
./include/linux/syscalls.h:233:18: warning: 'sys_mmap2' alias between
functions of incompatible types 'long int(long unsigned int, size_t,
long unsigned int, long unsigned int, long unsigned int, long
unsigned int)' {aka 'long int(long unsigned int, unsigned int, long
unsigned int, long unsigned int, long unsigned int, long unsigned
int)'} and 'long int(long int, long int, long int, long int, long
int, long int)' [-Wattribute-alias]
asmlinkage long sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)) \
^~~
./include/linux/syscalls.h:222:2: note: in expansion of macro
'__SYSCALL_DEFINEx'
__SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
^~~~~~~~~~~~~~~~~
./include/linux/syscalls.h:216:36: note: in expansion of macro
'SYSCALL_DEFINEx'
#define SYSCALL_DEFINE6(name, ...) SYSCALL_DEFINEx(6, _##name,
__VA_ARGS__)
^~~~~~~~~~~~~~~
arch/powerpc/kernel/syscalls.c:65:1: note: in expansion of macro
'SYSCALL_DEFINE6'
SYSCALL_DEFINE6(mmap2, unsigned long, addr, size_t, len,
^~~~~~~~~~~~~~~
./include/linux/syscalls.h:238:18: note: aliased declaration here
asmlinkage long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)) \
^~~~~~~~
./include/linux/syscalls.h:222:2: note: in expansion of macro
'__SYSCALL_DEFINEx'
__SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
^~~~~~~~~~~~~~~~~
./include/linux/syscalls.h:216:36: note: in expansion of macro
'SYSCALL_DEFINEx'
#define SYSCALL_DEFINE6(name, ...) SYSCALL_DEFINEx(6, _##name,
__VA_ARGS__)
^~~~~~~~~~~~~~~
arch/powerpc/kernel/syscalls.c:65:1: note: in expansion of macro
'SYSCALL_DEFINE6'
SYSCALL_DEFINE6(mmap2, unsigned long, addr, size_t, len,
^~~~~~~~~~~~~~~
This warning should detect serious problems, so don't disable it without
first investigating please.
It's been a discussion on this topic, ref
https://lkml.org/lkml/2017/12/5/581
It says "The new warning seems reasonable in principle, but it doesn't
help us here, since we rely on the type mismatch to sanitize the
system call arguments. After I reported this as GCC PR82435, a new
-Wno-attribute-alias option was added that could be used to turn the
warning off globally on the command line, but I'd prefer to do it a
little more fine-grained"
What do you call "latest version", btw? Trunk, aka 9.0? Or the most
advanced release, 8.1? Or the latest release (which also is 8.1 :-) )
I encounter it with 8.1
According the refered discusion, it linked to GCC 8
Christophe
Segher
