Stu Bell wrote:
> Trampolines work only for statically linked functions, not function
> pointers.
Sorry, but I don't understand this.
I believe that there is no problem with statically linked functions.
GCC actually generates a call with the full address, and no 16 bit
pointers are involved, as in the following disassembly:
butta = ButtamiViaSubito();
4014: 0f 94 f5 06 call 0x20dea ; 0x20dea
Here I am calling the same function but directly, and GCC generates the
correct code for the AtMega2561.
Actually, as I told in my previous mail, I tried a small program
where it seems to work.
Here is the main:
typedef void (*PPro)(void);
PPro ppro1;
extern void pro1(void) __attribute__ ((section ("spro1")));
int main(void)
{
ppro1 = pro1;
pro1();
ppro1();
while(1)
;
return(0);
}
Here is the function:
__attribute__((section ("spro1"))) void pro1(void)
{
return;
}
In the linker flags I added:
-section-start=spro1=0x21000
to place the routine in the upper 128K.
and the relevant disassembly is:
...
000000cc <__trampolines_start>:
cc: 0d 94 00 08 jmp 0x21000 ; 0x21000 <pro1>
...
ppro1 = pro1;
116: 86 e6 ldi r24, 0x66 ; 102
118: 90 e0 ldi r25, 0x00 ; 0
11a: 90 93 01 02 sts 0x0201, r25
11e: 80 93 00 02 sts 0x0200, r24
...
ppro1();
126: e0 91 00 02 lds r30, 0x0200
12a: f0 91 01 02 lds r31, 0x0201
12e: 19 95 eicall
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