Re: [Mspgcc-users] help!!

[Arnd-Hendrik Mathias]

Hi Vijay,
the first problem is a consequence of (as the linker says) multiple 
definitions: Definitions should never (!) be found in header files but 
rather in your .c files. Headers should only contain declarations 
(except macro definitions which is another part of the C language). The 
correct way to provide this is to change the definitions to extern 
declarations:

extern const __attribute__ ((section (".flashA"))) int SystemPrefix;

(...)

Subsequentially add the definition (without extern) of each of your 
constants (as well as variables) to a certain .c file which is 
guaranteed to be compiled and linked to the whole object.

To make the difference visible consider files a.h b.c and c.c in two 
cases: 1. File a.h contains definitions and 2. File a.h contains only 
declarations.
In both cases you would not compile the header file itself.

In the first case b.c including a.h is compiled, the compiler finds the 
definition and generates a constant (memory area with a name symbol for 
address resolution) in file b.o. Then c.c including a.h is compiled, the 
compiler does the same as described above for c.o. In the end The linker 
finds two memory areas trying to reserve both of them in memory (which 
might be the meaning/reason for your final error message: The double 
amount of mem space is needed to store all of your constants). Finally 
it tries to resolve references in code to the names and does not know 
which of two different addresses with the identical names shall be 
inserted for this reference.

In the second case b.c including a.h is compiled, the compiler reads the 
extern declaration and thereby learns that an externally defined symbol 
of a certain type will exist and can be referenced. Later in b.c it 
finds a reference to that symbol and knows that this reference will be 
resolved at link time. Then c.c including a.h is compiled, the compiler 
learns the symbol the same way as before. It then finds the definition 
(without extern) in the c.c file itself, checks for corresponding types 
(with the declaration) and defines a memory area with its name. Later 
the linker (linking b.o and c.o) puts this defined memory area to an own 
address and uses this address for resolving the references from b.o and c.o.

Regards

Arnd-Hendrik



Vijay wrote:
hai guys,

    i have another error, when i am compiling i am getting the following 
error....



Gsm.o(.flashA+0x6): In function `UartTaskComplete':
/cygdrive/c/Documents and Settings/Desktop/latestOBDISODriver/Gsm.c:38:
multiple definition of `OBDDY'
Main.o(.flashA+0x6):/cygdrive/c/Documents and Settings/Desktop/latestOBD
ISODriver/Main.c:38: first defined here
Gsm.o(.flashA+0x5a): In function `GsmTimeout':
/cygdrive/c/Documents and Settings/Desktop/latestOBDISODriver/Gsm.c:77:
multiple definition of `IMEINumber'
Main.o(.flashA+0x5a):/cygdrive/c/Documents and Settings/Desktop/latestOB
DISODriver/Main.c:110: first defined here
Gsm.o(.flashB+0x0): In function `UartTaskComplete':
/cygdrive/c/Documents and Settings/Desktop/latestOBDISODriver/Gsm.c:37:
multiple definition of `UserList'

msp430-ld: region data is full (JL2 section .flashA)
make: *** [JL2] Error 1

thes e varibles, like UserList,IMEINumber etc.. are flash variables and 
i have declared it as follows in the header file:



const __attribute__ ((section (".flashA"))) int SystemPrefix;

const __attribute__ ((section (".flashA"))) struct OBDDynamicVariables 
OBDDY[2];

const __attribute__ ((section (".flashA"))) struct OBDStaticVariables OBDST;

const __attribute__ ((section (".flashA"))) unsigned int IMEINumber[8];

const __attribute__ ((section (".flashA"))) unsigned int MyPhoneNumber[8];

const __attribute__ ((section (".flashA"))) unsigned int UserPhoneNumber[8];

const __attribute__ ((section (".flashA"))) int SystemStatus ;

i thought it might be becoz of multiple inclusion of header files,and i 
added

#ifndef <filename>

#define<filename>

........#endif

in all the header file, but still i am having this probelm, i refrred to 
the compile folder(mspgcc)in my drive and had a look in the ir include 
files , and did the same thing...of how they have included to avoid this 
..still i am helpless!! could any one suggest me ,to overcome this error,

thank you

vijay

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