Hi,
I know I am a bit late on the party.
But I have a question...
Consider this test case:
$ cat test.c
struct s {
int a, b;
} __attribute__((aligned(8)));
struct s f0;
int f(int a, int b, int c, int d, int e, struct s f)
{
f0 = f;
return __alignof(f);
}
$ arm-linux-gnueabihf-gcc -march=armv5te -O3 -S test.c
$ cat test.s
f:
@ args = 12, pretend = 0, frame = 0
@ frame_needed = 0, uses_anonymous_args = 0
@ link register save eliminated.
push {r4, r5}
mov r0, #8
ldrd r4, [sp, #12]
ldr r3, .L4
strd r4, [r3]
pop {r4, r5}
bx lr
I am pretty sure, although there is no warning, this ABI changed in GCC 5.2
http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0473m/dom1361290002364.html
says:
"In ARMv5TE, or in ARMv6 when SCTLR.U is 0, LDRD and STRD doubleword data
transfers must be
eight-byte aligned. Use ALIGN 8 before memory allocation directives such as
DCQ if the data
is to be accessed using LDRD or STRD. This is not required in ARMv6 when
SCTLR.U is 1, or in
ARMv7, because in these versions, doubleword data transfers can be
word-aligned."
So isn't this wrong code, returning 8 for alignof when it is really 4,
and wouldn't it crash on armv5 and armv6 with SCTLR.U=0 ?
Bernd.
