Linker errors with multiple file progam

nkhambal · #1 23-Apr-2005, 21:52

Hi,

I am trying to compile a program having multiple files. I have a common header file which i am including in 3 source files. Multiple inclusion is protected by wrapping the contents of .h file using "#ifndef"

For e.g. I have following in my header file

CPP / C++ / C Code:

#ifndef PPTPCLIENT_H
#define PPTPCLIENT_H

const char control_reply_result_codes[6][100] = {	
	" ",
	"Successful channel establishment",
	"General error -- Error Codeindicates the problem",
	"Command channel already exists",
	"Requester is not authorized to establish a command channel",
	"The protocol version of the requester is not supported"
};

const char general_error_codes[6][100] = { 
	"No General Error",
	"No Control Connection exits yet for this PAC-PNS pair",
	"Length is wrong or Magic Cookie value is incorrect",
	"One of the field values was out of range or reserved field was non-zero",
	"The Call ID is invalid in this context",
	"A generic vendor-specific error occured in the PAC"
};

const char stop_reason_codes[4][100] = { 
	" ",
	"General request to clear control connection",
	"Can't support peer's version of the protocol",
	"Requester is being shutdown"
};

const char og_result_code [8][150] = {	
	" ",
	"Call established with no errors",
	"Outgoing call not established for the reason indicated in error code",
	"Outgoing call failed due to no carrier detected",
	"Outgoing call failed due to detection of busy signal",
	"Outgoing Call failed due to lack of a dial tone",
	"Outgoing Call was not established within time allotted by PAC",
	"Outgoing Call administratively prohibited"
};
....../*Some other similar declarations */
#endif

How ever I am getting linker errors for multiple inclusion of above array and similar other arrays.

Quote:

gcc -g -o pptpclient pclientmain.c pclientfunction.c pptputils.c
/tmp/ccMMMtIa.o(.rodata+0x0): In function `printHelp':
/home/snoopy/pptp/pclientfunction.c:4: multiple definition of `control_reply_result_codes'
/tmp/cccyJsV6.o(.rodata+0x0):/home/snoopy/pptp/pclientmain.c:4: first defined here
/tmp/ccMMMtIa.o(.rodata+0x260): multiple definition of `general_error_codes'
/tmp/cccyJsV6.o(.rodata+0x260): first defined here
/tmp/ccMMMtIa.o(.rodata+0x4c0): multiple definition of `stop_reason_codes'
/tmp/cccyJsV6.o(.rodata+0x4c0): first defined here
/tmp/ccMMMtIa.o(.rodata+0x660): multiple definition of `og_result_code'
/tmp/cccyJsV6.o(.rodata+0x660): first defined here

Can some one help me to figure out where the problem is?

Thanks,

WaltP · #2 24-Apr-2005, 00:46

Quote:

Originally Posted by nkhambal

Hi,

I am trying to compile a program having multiple files. I have a common header file which i am including in 3 source files. Multiple inclusion is protected by wrapping the contents of .h file using "#ifndef"

For e.g. I have following in my header file

CPP / C++ / C Code:

#ifndef PPTPCLIENT_H
#define PPTPCLIENT_H

externalconst char control_reply_result_codes[6][100];
const char general_error_codes[6][100] = { 
	"No General Error",
	"No Control Connection exits yet for this PAC-PNS pair",
	"Length is wrong or Magic Cookie value is incorrect",
	"One of the field values was out of range or reserved field was non-zero",
	"The Call ID is invalid in this context",
	"A generic vendor-specific error occured in the PAC"
};

const char stop_reason_codes[4][100] = { 
	" ",
	"General request to clear control connection",
	"Can't support peer's version of the protocol",
	"Requester is being shutdown"
};

const char og_result_code [8][150] = {	
	" ",
	"Call established with no errors",
	"Outgoing call not established for the reason indicated in error code",
	"Outgoing call failed due to no carrier detected",
	"Outgoing call failed due to detection of busy signal",
	"Outgoing Call failed due to lack of a dial tone",
	"Outgoing Call was not established within time allotted by PAC",
	"Outgoing Call administratively prohibited"
};
....../*Some other similar declarations */
#endif

How ever I am getting linker errors for multiple inclusion of above array and similar other arrays.

Can some one help me to figure out where the problem is?

Thanks,

Never define data in your header file. They are for delarations only. Put the contents of your header file in one of the source files and change all definitions to externals:

CPP / C++ / C Code:

extern char control_reply_result_codes[6][100];
extern char general_error_codes[6][100];
...

The wrapping, called header guards only prevent inclusion in the same source file. They are used when you have a complicated set of headers, and the possibility of a header being including more than once because of nested headers (headers including headers which include more headers).

What you tried to do is prevent the multiple definitions in the other files. If it worked the way you expected, none of the variables would have been defined in 2 of the three files. You might as well just leave the .h file out.

What you in fact did is define the variables control_reply_result_codes, general_error_codes, et al in each source file. Complete with your string definitions.

The .h files should not "reserve variable space", only declare the variable exists. The source files reserve the space.

nkhambal · #3 24-Apr-2005, 02:37

Hi Walt,

Thanks. That did the trick. It is my first attempt to write a program that spans more than 2 source files. Good I got things cleared now.

Much appricated.

Thanks,

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Linker errors with multiple file progam

Thanks. That worked.