What for linker read-only memory section exists?
I declared in linker script new memory region (ROM), defined as read only:
MEMORY
{
text (rx) : ORIGIN = 0, LENGTH = 128K
/*data (rw!x) : ORIGIN = 0x800060, LENGTH = 0xffa0*/
data (rw!x) : ORIGIN = 0x800060, LENGTH = 0x7fa0
ROM (r) : ORIGIN = 0x808000, LENGTH = 0x7fff
eeprom (rw!x) : ORIGIN = 0x810000, LENGTH = 64K
fuse (rw!x) : ORIGIN = 0x820000, LENGTH = 1K
lock (rw!x) : ORIGIN = 0x830000, LENGTH = 1K
signature (rw!x) : ORIGIN = 0x840000, LENGTH = 1K
}
Next, I put into it new section:
.XMEM :
{
*(.XMEM*)
} > ROM
Everything is fine, my variables go where I wanted. I expected that read only memory section is read only, so every attempt to write something into it will result a linker error. So the test program:
#define XMEM __attribute__ ((section (".XMEM")))
XMEM int xx2;
int XMEM xx3;
int main()
{
xx2=10;
xx3=xx2+1;
}
Should not compile. But it compiles without any problems, warnings, errors, etc. I checked generated map file and everything is as I expected:
Name Origin Length Attributes
text 0x00000000 0x00020000 xr
data 0x00800060 0x00007fa0 rw !x
ROM 0x00808000 0x00007fff r
eeprom 0x00810000 0x00010000 rw !x
fuse 0x00820000 0x00000400 rw !x
lock 0x00830000 0x00000400 rw !x
signature 0x00840000 0x00000400 rw !x
*default* 0x00000000 0xffffffff
"¦
.XMEM 0x00808000 0x6
*(.XMEM*)
.XMEM 0x00808000 0x6 ksiazka.o
0x00808002 xx2
0x00808000 xx1
0x00808004 xx3
So what for is read only attribute? Or how I can force gcc to generate warnings/errors when attempt to read only memory section is performed?
