On Tuesday 21 June 2011 01:50 PM, Wolfgang Denk wrote:
Dear Aneesh,
In message4E00447B.9070804@ti.com you wrote:
$ gcc main.c main.c:5: error: initializer element is not constant main.c:5: error: (near initialization for ‘arr[0]’) main.c:7: error: initializer element is not constant main.c:7: error: (near initialization for ‘arr[1]’)
I have to admit that I don't understand either why this error is raised here; after all, from our understanding of the code these _are_ constant addresses.
You may want to ask this in a compiler group...
Yes. I will.
As a result, I will have to do something like this to populate my array:
static unsigned int *const reg_arr[] = { &(((struct my_regs_struct *const)OMAP4_PRCM_REG_BASE)->uart_clkctrl), &(((struct my_regs_struct *const)OMAP4_PRCM_REG_BASE)->i2c_clkctrl), };
Is this acceptable?
No, please don't.
Note that the following code compiles fine:
----------------------------- snip ----------------------------- #include<stdio.h>
struct my_regs_struct { unsigned int reg1; unsigned int reg2; unsigned int reg3; };
static struct my_regs_struct *const my_regs = (struct my_regs_struct *) 0x1000;
static void print_regs(void) { unsigned int *const reg_arr[] = { &my_regs->reg1, &my_regs->reg3, }; printf("regs %p %p \n", (void *)reg_arr[0], (void *)reg_arr[1]); }
In my function I am using 3 such arrays with quite a few entries in them. Won't it look ugly besides increasing the stack footprint.
Of course, I can try to break them down to different functions, if need be.
Or, how about using a utility macro and make it look better like this:
#define OMAP4_PRCM_REG_ADDR(reg)\ (&(((struct my_regs_struct *)OMAP4_PRCM_BASE)->reg))
static unsigned int *const reg_arr[] = { OMAP4_PRCM_REG_ADDR(uart_clkctrl), OMAP4_PRCM_REG_ADDR(i2c_clkctrl) };
This one doesn't generate any warning even with 'gcc -Wall -pedantic'.
Are you not comfortable with getting the address in this manner at all?
best regards, Aneesh