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when I define a variable like next: uchar idata M_TVar _at_ 0x80; I got a warning: *** WARNING L4: DATA SPACE MEMORY OVERLAP FROM: 0000H TO: 0001H
the next is in .M51 file:
* * * * * * * D A T A M E M O R Y * * * * * * * IDATA 0000H 0001H ABSOLUTE * OVERLAP * IDATA 0000H 0001H ABSOLUTE * OVERLAP * REG 0000H 0008H ABSOLUTE "REG BANK 0" DATA 0008H 0040H UNIT ?DT?MAIN
how i fix it?
I have resolved that problem
the error is in the define of variable in my head file: the old: #ifdef GLOBAL_VAR #define EXT_VR #else #define EXT_VR extern EXT_VR uchar idata M_TVar _at_ 0x80;
And I use the file in two files: fileA.c and fileB.c
and the newest file writen as: #ifdef GLOBAL_VAR #define EXT_VR EXT_VR uchar idata M_TVar _at_ 0x80; #else #define EXT_VR extern EXT_VR uchar idata M_TVar;// _at_ 0x80; So it works good. but I don't know why. may be Keil just do it in that way;
thanks for every body!!
by the way, must define GLOBAL_VAR once before include headfile in one of C files.
"but I don't know why"
The _at_ is only meaningful on a definition - not in a declaration
ie, _at_ doesn't make sense with extern!
You need something like
#ifdef DEFINE_GLOBAL // Make a definition #define EXT_ABS(name,loc) uchar idata name _at_ loc #else // Make an extern declaration #define EXT_ABS(name,loc) extern uchar idata name #else EXT_ABS( M_TVar, 0x80 );
#ifdef GLOBAL_VAR #define EXT_VR #else #define EXT_VR extern
I suggest you do yourself a favour and get rid of this supposed "trick". It may seem like a major advantage to only have to write declarations once, but
1) it only works for a subset of globals --- if you have an explicit initializer, you have to write the definition and declaration separately again.
2) it puts stuff into the interface (header) that shouldn't be there: the initializers.
3) it shoves all globals of the entire program into one translation unit (which has to include all header files, too). That can make it needlessly hard for the linker to fit all those variable into memory, especially if memory space is fragmented.