I am kind of confused about using the _at_ keyword to assign a specific address to a variable.
so for example :
extern xdata char variable _at_ 0x000f;
it fills 3 bytes in xram . can any one explain how is the compiler handling these sequence. Thank you !
"1) definition/declaration can be found as synonyms in any crossword handbook."
But, as already noted, we are not talking about crossword puzzles! We are talking about the 'C' programming language, where the terms have specific, distinct meanings - and a thorough understanding of the distinction is key to this thread!
"2) an extern is NOT a definition, it is a reference"
No, it is not a reference, it is a declaration
I stand corrected re verbiage; however the reason I stated for the problem (extern combined with _at_) was correct and the OP changed accordingly and now states "it works".
Erik
I stand corrected re verbiage
Thank goodness for that.
however the reason I stated for the problem (extern combined with _at_) was correct and the OP changed accordingly and now states "it works".
Well actually, the problem reported was this:
it fills 3 bytes in xram
And you replied:
it fills 3 bytes in xram is definitely wrong, but not the issue
Yet you are now claiming it was intended as a fix for the issue. Can you explain?
when the mistake is glaring, I usually provide a hint rather than a solution (I know that a hint will lead to better understanding if the asker work on the hint), then when both the OP and you gave up I posted
the _at_ must be ... not in an extern
and, amazing to you, I am sure, the 3 byte issue disappeared
Jack, Erik, I need to apologize to you. My posted test above was wrong in the sense that when using the RealView compiler, one should make the declaration like this:
extern int variable __attribute__((at(0x8000))) ;
and not like the original version, which was
extern int variable __attribute__((__at(0x8000))) ;
when the first one is used - no warning is generated!