Hello,
I define a constant in the linker script and want access it from C-code:
SECTIONS
{
...
_bootsize = 0x00004000;
...
}
Here is code snippet:
extern unsigned long _bootsize;
char message[10];
...
siprintf(message, "Bootsize: 0x%x\n\r", _bootsize);
AT91F_DBGU_Frame(message);
But it always prints out "Bootsize: 0x2004d4" Why so?
As far as I understand, it's quite possible to do what I want.
Roman Mashak wrote: > Hello, > > I define a constant in the linker script and want access it from C-code: > > SECTIONS > { > ... > _bootsize = 0x00004000; > ... > } > > Here is code snippet: > > extern unsigned long _bootsize; > char message[10]; > ... > siprintf(message, "Bootsize: 0x%x\n\r", _bootsize); > AT91F_DBGU_Frame(message); > > But it always prints out "Bootsize: 0x2004d4" Why so? > As far as I understand, it's quite possible to do what I want. Looking at the documentation here: http://sourceware.org/binutils/docs-2.18/ld/Source-Code-Reference.html#Source-Code-Reference If I understood it right _bootsize is the address of your constant, the constant is allocated there as a word.
Roman Mashak wrote: > Hello, > > I define a constant in the linker script and want access it from C-code: > > SECTIONS > { > ... > _bootsize = 0x00004000; > ... > } > > Here is code snippet: > > extern unsigned long _bootsize; > char message[10]; > ... > siprintf(message, "Bootsize: 0x%x\n\r", _bootsize); > AT91F_DBGU_Frame(message); > > But it always prints out "Bootsize: 0x2004d4" Why so? > As far as I understand, it's quite possible to do what I want. Look at a sample here with the file syscall.c, you will have a sample on how to access a constant address from C source. Jonathan
Giovanni Di Sirio wrote: > Looking at the documentation here: > http://sourceware.org/binutils/docs-2.18/ld/Source-Code-Reference.html#Source-Code-Reference > > If I understood it right _bootsize is the address of your constant, the > constant is allocated there as a word. Hm.. After reading documentation at the link, I come to the conclusion that there is no way to assign a value to a linker script defined symbol. Such symbol will always hold only address. Am I right, there is no way to get what I want?
Jonathan Dumaresq wrote: > Look at a sample here with the file syscall.c, you will have a sample on > how to access a constant address from C source. Before posting I studied that code and did as in there. It seems I can't achieve what I need: to define a constant value in a linker script and use it from the C code.
Giovanni Di Sirio wrote: > Looking at the documentation here: > http://sourceware.org/binutils/docs-2.18/ld/Source-Code-Reference.html#Source-Code-Reference I must have read the link thoughtlessly the first time and missed the point. Now I got it right - accessing the symbol defined in linker script as "&_bootsize" works fine for me. Thanks again.