Re: Array size depending on symbol address

usenet@xxxxxxx wrote: 
Hello,

I am running my code on an embedded platform without OS. I have defined some
data in a section called .eeprom. The section is defined by the linker
script and starts at address zero. The symbol __eeprom_end is defined by the
linker script as well, and lies at the end of this section. The address of
__eeprom_end is thus equal to the number of bytes in the .eeprom section.

My problem : I want to declare an array in .bss with the same size of this
section. My naive approch was :

  extern void *_eeprom;
  char eeprom_shadow[(int)&_eeprom_end];

This fails miserably, ofcourse : the compiler doesn't know the address of
__eeprom before the linker is done, so it can not declare the array.

Is there a trick to allocate the memory for this array at compile time ?

Your identifiers are all over each other. Is _eeprom the address of the section .eeprom? Is _eeprom_end a typo or intended to be the same as __eeprom_end? What is __eeprom with two underscores?

In any case, as you say, all this information is available at link time. There is simply no way to turn these symbols or their addresses into compile-time constants if you don't already have the information available, and global array sizes must be compile-time constants.

Any reason why you can't have the linker declare a section .eeprom_shadow of equal size and use the address of that? Indexing would work the same; the only restriction is that you still don't know the size at compile time, but that shouldn't be too much of a problem, since you'd have __eeprom_end (or _eeprom_end) available at runtime.

S.
.

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