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Easiest question in the world? Linker error in CCS build - Undefined sysmbol

Rich Mullen
Intellectual 325 points

Hi, I'm just starting out in CCS. I've got the project set up, have a main.c which calls a single function,    InitHardware();.

I have a file called Init_Hardware.cpp that defines void InitHardware(void);

And a file called Init_Hardware.cpp that has the code for void InitHardware(void) { P1DIR = 0x00;};

main.c does include Init_Hardware.hpp as the linker map verifies this

When I build this I get an undefined symbol error.

 undefined    first referenced
  symbol          in file    
 ---------    ----------------
 InitHardware ./main.obj

  For the life of me I can't figure out why. Any help would be appreciated and any insult about my programming prowess would be accepted.. 

  Thanks!

Rich

 

 

 

 

  • 0
    TI__Guru**** 173310 points

    Rich,

    When mixing C and C++ code, use the C linkage convention (extern "C") on your C++ function declarations.

    More details are in this wiki page: http://processors.wiki.ti.com/index.php/Overview_of_C%2B%2B_Support_in_TI_Compilers#Name_Mangling

  • 0 in reply to AartiG
    Intellectual 325 points

    Thanks for the reply - in my header file, entire file below, I did try an extern declaration, but I got an error message #41 - expected an identifier. And the build stops without linking.

    The commented out code with no extern didn't return an error here, but it did give the unresolved symbol message, which I understand now from your post..

    //
    ///  Init_Hardware.hpp Header file
    //
    //////////////////////////////////////
    //
    //
    //void InitHardware(void);
    extern "C" void InitHardware(void);
    //

    Is there something wrong in the extern declaration, does the code also need the extern? - though I did try that.

    -Rich

  • 0 in reply to Rich Mullen
    TI__Guru**** 173310 points

    Rich,

    Please see the attached files with which I was able to build without errors.

    0878.test.zip

  • 0 in reply to AartiG
    Intellectual 325 points

    Thanks! It worked great. I wasn't aware that the __cplusplus definition could and should be used at this point. I appreciate your time!

    -Rich

     

  • 0 in reply to AartiG
    TI__Mastermind 29705 points

    Hi Aarti,

    I am trying to interface C with ASM as described at page 132 of ARM compiler SPNU151G.

    Taking the given C and ASM code of page 132 I am getting the same error with comparable syntax (but for different prupose):

    extern "C" {
    extern int asmfunc(int a); /* declare external asm function */
    int gvar = 0; /* define global variable */
    }

    **** Build of configuration Debug for project AM335x_basic ****

    /home/sitara/ti/ccsv5/utils/bin/gmake -k all
    Building file: ../hello.c
    Invoking: ARM Compiler
    "/home/sitara/ti/ccsv5/tools/compiler/tms470/bin/cl470" -mv7A8 --code_state=32 --abi=eabi -me -g --include_path="/home/sitara/ti/ccsv5/tools/compiler/tms470/include" --diag_warning=225 --display_error_number --preproc_with_compile --preproc_dependency="hello.pp"  "../hello.c"
    "../hello.c", line 7: error #41: expected an identifier

    >> Compilation failure
    "../hello.c", line 7: error #66: expected a ";"

    where line 7 is extern "C" {.

    Is there a know issue to interface ASM and C in CGTools 4.9.1 with  CCS 5.1.1.00033?
    Or are there specific compiler options that are needed for this?

    Thanks in advance and best regards,

    Anthony

  • 0 in reply to AnBer
    TI__Guru* 84225 points

    extern "C" is not legal C code, it is C++ code.  You must do this in a header file which is shared between C and C++ modules:

    #ifdef __cplusplus
extern "C" {
#endif
extern int asmfunc(int a); /* declare external asm function */
int gvar = 0; /* define global variable */
#ifdef __cplusplus
}
#endif

    [Edit: should be ifdef, not ifndef --Archaeologist]