https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51628
W.H. Ding <dingcurie at icloud dot com> changed:
What |Removed |Added
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CC| |dingcurie at icloud dot com
--- Comment #47 from W.H. Ding <dingcurie at icloud dot com> ---
Hi, everyone
I wonder if this issue has to do with the bug-like problem I encountered when
accessing an unaligned stand-alone global variable (rather than a member of a
packed struct). A test case is as follows:
char g_c = 'x';
int g_d __attribute__((aligned(1))) = 13;
int main(void)
{
g_c = 'z';
//================
g_d = 33; // Crash on, in my case, ARM Cortex-M0
//================
return 0;
}
Due to the presence of g_c, g_d is at an odd address, as the map file
indicates:
.data.g_c 0x20000020 0x1 ./src/test.o
0x20000020 g_c
.data.g_d 0x20000021 0x4 ./src/test.o
0x20000021 g_d
The generated assembly, however, accesses g_d as if it were properly aligned:
8:../src/test.c **** //================
9:../src/test.c **** g_d = 33;
52 .loc 1 9 0
53 000a 044B ldr r3, .L2+4
54 000c 2122 movs r2, #33
55 000e 1A60 str r2, [r3]
10:../src/test.c **** //================
BTW: I'm using GNU ARM Embedded Toolchain 7-2017-q4-major and on Windows 7.
Any ideas?
