multiple definition of '_symbolname' first defined here

[vijitron]

i am using the structure and got this mulitlple definition issue,
Error: (Compiler: XC16 MPLAB X IDE)
build/default/production/drv/CC112X/Drv/Radio.o(.nbss+0x2): multiple definition of `_RadioChipType'
build/default/production/main.o(.nbss+0x0): first defined here

My structure in Radio_if.h file

---

Code C - [expand]
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typedef struct
{
 unsigned int deviceName;
 unsigned int id;
 unsigned int ver;
 unsigned int xoscFreq;
 
}radioChipType_t;
 
radioChipType_t RadioChipType;

---

i included this Radio_if.h file in Radio.c file and the Main.c file.
I added the Radio.c file in source folder of project in Mplab X.

i written the below as well to avoid multiple includes

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Code C - [expand]
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#ifndef RADIO_IF_H
#define    RADIO_IF_H
 
#ifdef    __cplusplus
extern "C" {
#endif
 
 
//codes here
 
 
#ifdef    __cplusplus
}
#endif
 
#endif

---

Can any help me why this error comes in

 

[horace1]

the statemen

t in Radio_if.h

radioChipType_t RadioChipType;

defines the variable RadioChipType, i.e. allocates memory for it

therefore if you include Radio_if.h in Radio.c and main.c you end up with two definitions and hence get the "multiple definition of `_RadioChipType'"

to overcome the problem declare RadioChipType as extern in the header file

typedef struct
{
 unsigned int deviceName;
 unsigned int id;
 unsigned int ver;
 unsigned int xoscFreq;
 
}radioChipType_t;
 
extern radioChipType_t RadioChipType;

and define it in Radio.c

radioChipType_t RadioChipType;

the program then only has one definition of RadioChipType in radio.C in all files it would be declared extern

 

[vijitron]

Hi Horace

I understood this thank you, i had 2 more doubts in this same topic.
1. This same code is working in Hitech PICC8 without the 'extern' i don't know how?
2. I used the extern as below in radio_if.h

extern radioChipType_t RadioChipType;
but not defined in Radio.c file, but its compiling without error.

I am having another structure

typedef struct
{
  unsigned char data[PER_MAX_DATA];
   char  rssi;
  unsigned char lqi;
  unsigned char length;
  unsigned char addr;
}rxData_t;
/* Used to hold RX data accross different radios. No Mutex is implemented */
extern rxData_t *rxData;

i added extern both the structure variables after your reply. and compiled only this structure pointer throws error as

"undefined reference to `_rxData'

Can you explain how the non pointer structure is working without define, and this pointer structure says error.

 

[horace1]

Hi Horace

I understood this thank you, i had 2 more doubts in this same topic.
1. This same code is working in Hitech PICC8 without the 'extern' i don't know how?
2. I used the extern as below in radio_if.h

extern radioChipType_t RadioChipType;
but not defined in Radio.c file, but its compiling without error.

I am having another structure

typedef struct
{
  unsigned char data[PER_MAX_DATA];
   char  rssi;
  unsigned char lqi;
  unsigned char length;
  unsigned char addr;
}rxData_t;
/* Used to hold RX data accross different radios. No Mutex is implemented */
extern rxData_t *rxData;

i added extern both the structure variables after your reply. and compiled only this structure pointer throws error as

"undefined reference to `_rxData'

Can you explain how the non pointer structure is working without define, and this pointer structure says error.

do you actually reference (use) the variable RadioChipType anywhere in Radio.c or Main.c?

you can declare an exern

extern radioChipType_t RadioChipType;

and not define it with

radioChipType_t RadioChipType;

so long as it is not referenced - as soon as you rattempt to reference it you will get "undefined reference"