MCUXpresso GeneralのトピックRe: Including header files problem

Including header files problem

jussikangas — Sun, 25 Apr 2021 18:26:39 GMT

I have problem when including same header file from two different source files I get error from duplicate variables.

Variable is defined in PID.h

I have PID.h that is included in PID.c and main.c.

Now I trying to port my code to work in LPCXpresso.

I have been using eclipse and gcc before, and this same code and files has been working in that environment.

./src/main.o:(.bss.PID+0x0): multiple definition of `PID'
AHB_SRAM1: 1048 B 32 KB 3.20%
./src/PID.o:(.bss.PID+0x0): first defined here
collect2.exe: error: ld returned 1 exit status

Header files are located in separate holder just to keep thing clean.

It's include path is defined as:

"${workspace_loc:/${ProjName}/inc}"

Re: Including header files problem

ErichStyger — Sun, 25 Apr 2021 18:39:59 GMT

Variable is defined in PID.h

That's the problem. Header files are for *declarations*, not definitions!

You probably missed the 'exern' in the header file, it shall be for example

extern int pid;

in the header file pid.h und

int pid;

in the pid.c

I hope this helps,

Erich

Re: Including header files problem

jussikangas — Sun, 25 Apr 2021 19:36:17 GMT

Hello

That is a way that I use header for declarations and in source files variables are defined.

It seems that my old tool chain handled those pit different.

I changed according your advice and now code is build fine.

Thanks

Re: Including header files problem

ErichStyger — Mon, 26 Apr 2021 03:37:48 GMT

It depends on the linker if it flags double definitions. I consider this as a programmer error so having it flagged as an error is a good thing.