GCC does not use @... at least not like this.
Generally to access a specific memory location in a certain way I use
something like this:
struct foo __attribute__ ((packed)) {
uint8_t a : 1;
uint8_t b : 1;
uint8_t c : 1;
uint8_t d : 1;
uint8_t reserved : 4;
};
#define FOO (*((volatile struct foo *) 0x40005C00))
FOO.a = 1;
regards,
m.s.
On Sun, 2013-10-20 at 00:13 -0300, Peter Gregson wrote:
> Hello,
>
> Perhaps you can help me. I have a piece of code that I am porting to GCC and one of the macros has been giving me problems for over a week. Could you please look at it and tell me what is wrong? Note that this is extracted from the actual code, and is, I think, the smallest amount that shows the problem.
>
>
> First the code:
>
> /* Test macro defs */
>
> #define __REG16 unsigned short
>
> #define __READ_WRITE const
>
> typedef struct {
> __REG16 EA : 4;
> __REG16 STATTX : 2;
> __REG16 DTOGTX : 1;
> __REG16 CTRTX : 1;
> __REG16 EPKIND : 1;
> __REG16 EPTYPE : 2;
> __REG16 SETUP : 1;
> __REG16 STATRX : 2;
> __REG16 DTOGRX : 1;
> __REG16 CTRRX : 1;
> } __usb_epr_bits;
>
> #define __IO_REG16(NAME, ADDRESS, ATTRIBUTE) \
> volatile __no_init ATTRIBUTE unsigned short NAME @ ADDRESS
>
>
>
> #define __IO_REG16_BIT(NAME, ADDRESS, ATTRIBUTE,BIT_STRUCT)\
> volatile __no_init ATTRIBUTE union\
> {unsigned short NAME; \
> BIT_STRUCT NAME ## _bit; \
> } @ ADDRESS
>
>
>
> int main (void) {
>
> unsigned short USB_EP0R;
>
> __IO_REG16_BIT (USB_EP0R, 0x40005C00,__READ_WRITE,__usb_epr_bits);
> return (0);
> }
>
>
>
>
> Now the error message when I compile it. Note that I have "--save-temps" in the compiler invocation so that I can see the output of the preprocessor. I also used -O0 to keep things simple.
>
> Peters-MacBook-Air:STM32F103-STK peter$ gcc -O0 --save-temps -I USB tt.c
> tt.c: In function ‘main’:
> tt.c:39: error: nested functions are disabled, use -fnested-functions to re-enable
> tt.c:39: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘const’
> tt.c:39: error: stray ‘@’ in program
> tt.c:39: error: expected identifier or ‘(’ before numeric constant
> Peters-MacBook-Air:STM32F103-STK peter$
>
>
>
> When I add -fnested-functions to the command line, I get :
>
> Peters-MacBook-Air:STM32F103-STK peter$ gcc -O0 --save-temps -I USB -fnested-functions tt.c
> tt.c: In function ‘main’:
> tt.c:39: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘const’
> tt.c:39: error: stray ‘@’ in program
> tt.c:39: error: expected identifier or ‘(’ before numeric constant
> Peters-MacBook-Air:STM32F103-STK peter$
>
>
> The output of the preprocessor is as follows. You can see that the macro substitution has been carried out, and it appears to my eye, correctly.
>
> # 1 "tt.c"
> # 1 "<built-in>"
> # 1 "<command-line>"
> # 1 "tt.c"
> # 9 "tt.c"
> typedef struct {
> unsigned short EA : 4;
> unsigned short STATTX : 2;
> unsigned short DTOGTX : 1;
> unsigned short CTRTX : 1;
> unsigned short EPKIND : 1;
> unsigned short EPTYPE : 2;
> unsigned short SETUP : 1;
> unsigned short STATRX : 2;
> unsigned short DTOGRX : 1;
> unsigned short CTRRX : 1;
> } __usb_epr_bits;
> # 35 "tt.c"
> int main (void) {
>
> unsigned short USB_EP0R;
>
> volatile __no_init const union {unsigned short USB_EP0R; __usb_epr_bits USB_EP0R_bit; } @ 0x40005C00;
>
> return (0);
> }
>
>
> I have the following questions:
>
> 1.What are my errors?
> 2. What is the "@" syntax about? I think that it means that he union is saved at absolute address 0x40005C00, but when I search on GCC "@" I get nothing.
>
> Can you help me, please?
>
> Thank you, and
>
> Best regards,
>
> Peter
>
>
