# ARM under C & C++ **URL:** \ **Category:** Kernel\ **Created:** [February 18, 2006, 8:46pm UTC](https://forums.freertos.org/t/arm-under-c-c/5305 "2006-02-18T20:46:29Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![system](https://d2v6vdsk2p900z.cloudfront.net/original/1X/7fc8fdb729c645aab5b20282bbe34e57cb407be6.jpeg) [@system](https://forums.freertos.org/u/system)\ **Post date:** [February 18, 2006, 8:46pm UTC](https://forums.freertos.org/t/arm-under-c-c/5305/1 "2006-02-18T20:46:29Z")
**nobody** wrote on [Saturday, February 18, 2006](https://sourceforge.net/p/freertos/discussion/382005/thread/ea716e73/#cd3f): I’m trying to compile a program under FreeRTOS with IAR compiler and if I use C as language all compile without problems, but if I use embedded C++ or extended embedded C++ I obtain always the following errors: Error[e46]: Undefined external “AT91F\_LowLevelInit” referred in ?RESET ( C:\Empresa\ Inicio\Debug\Obj\Cstartup.r79 ) Error[e46]: Undefined external “vTaskSwitchContext” referred in portasm ( C:\Empresa\Inicio\ Debug\Obj\portasm.r79 ) Error[e46]: Undefined external “vTaskIncrementTick” referred in portasm ( C:\Empresa\ Inicio\Debug\Obj\portasm.r79 ) I tought that FreeRTOS supports C++ programming but I’m not sure. If FreeRTOS supports C++ someone have an example of IAR compiler settings?? I’m developing with ARM7 AT91SAM7A3. Thanks. ---
**Author:** ![system](https://d2v6vdsk2p900z.cloudfront.net/original/1X/7fc8fdb729c645aab5b20282bbe34e57cb407be6.jpeg) [@system](https://forums.freertos.org/u/system)\ **Post date:** [February 18, 2006, 10:43pm UTC](https://forums.freertos.org/t/arm-under-c-c/5305/2 "2006-02-18T22:43:39Z")
**nobody** wrote on [Saturday, February 18, 2006](https://sourceforge.net/p/freertos/discussion/382005/thread/ea716e73/#cd3f/3af4): I suspect it cannot find the functions because of C++ mangling the names.  Try using extern "C" on the functions that are called from asm code. ---
**Author:** ![system](https://d2v6vdsk2p900z.cloudfront.net/original/1X/7fc8fdb729c645aab5b20282bbe34e57cb407be6.jpeg) [@system](https://forums.freertos.org/u/system)\ **Post date:** [February 18, 2006, 11:13pm UTC](https://forums.freertos.org/t/arm-under-c-c/5305/3 "2006-02-18T23:13:52Z")
**nobody** wrote on [Saturday, February 18, 2006](https://sourceforge.net/p/freertos/discussion/382005/thread/ea716e73/#cd3f/0c7a): Thanks, but I think that you didn`t understand the question. I don’t use asm code. I have problems with C++ code. For example, I have depeloped a class for encapsulate the task funcionality, I can compile the project with this class without problems, but when I write code for instance this class in my main function I have errors linking the project. The errors are the following: Linking Error[e46]: Undefined external “xTaskCreate(pdTASK\_CODE, signed char const \*, unsigned  short, void \*, unsigned long, void \* \*)” referred in ITask ( C:\Empresa\Inicio\Debug\Obj\ ITask.r79 ) Error[e46]: Undefined external “xTaskGetTickCount()” referred in ITask ( C:\Empresa\Inicio\ Debug\Obj\ITask.r79 ) Error[e46]: Undefined external “vTaskDelayUntil(portTickType \*, portTickType)” referred in  ITask ( C:\Empresa\Inicio\Debug\Obj\ITask.r79 ) Error[e46]: Undefined external “vTaskDelete(void \*)” referred in ITask ( C:\Empresa\Inicio\ Debug\Obj\ITask.r79 ) Error[e46]: Undefined external “vTaskStartScheduler()” referred in main ( C:\Empresa\Inicio\ Debug\Obj\main.r79 ) Someone have any idea??? Thanks ---
**Author:** ![system](https://d2v6vdsk2p900z.cloudfront.net/original/1X/7fc8fdb729c645aab5b20282bbe34e57cb407be6.jpeg) [@system](https://forums.freertos.org/u/system)\ **Post date:** [February 19, 2006, 8:42am UTC](https://forums.freertos.org/t/arm-under-c-c/5305/4 "2006-02-19T08:42:25Z")
**nobody** wrote on [Sunday, February 19, 2006](https://sourceforge.net/p/freertos/discussion/382005/thread/ea716e73/#cd3f/0c7a/5804): While it may not be asm related it still sounds like the same problem.  Are you compiling some files as c++ and some as c?  If so they will not link.  You need to compile it all as c++ (in which case I’m not sure it will work) or declare the c code as extern “c” (in which case it may work depending on what you are doing with the c++ code). If you are not sure what this answer means then I suggest reading up a bit on mixing c and c++. ---
**Author:** ![system](https://d2v6vdsk2p900z.cloudfront.net/original/1X/7fc8fdb729c645aab5b20282bbe34e57cb407be6.jpeg) [@system](https://forums.freertos.org/u/system)\ **Post date:** [February 20, 2006, 8:23am UTC](https://forums.freertos.org/t/arm-under-c-c/5305/5 "2006-02-20T08:23:05Z")
**[jra01](https://sourceforge.net/u/jra01/)** wrote on [Monday, February 20, 2006](https://sourceforge.net/p/freertos/discussion/382005/thread/ea716e73/#cd3f/0c7a/8e00): Maybe the problem is that the compiler doesn’t see the extern “C” when compiling the OS, but when it compiles the c++ code. Therefore the C++ expects unmangled names, but the OS functions are mangled. Look in your link listing if you can find mangled versions of the OS functions (in case you get a listing even with failed links). Jokke ---
**Author:** ![system](https://d2v6vdsk2p900z.cloudfront.net/original/1X/7fc8fdb729c645aab5b20282bbe34e57cb407be6.jpeg) [@system](https://forums.freertos.org/u/system)\ **Post date:** [February 20, 2006, 8:51am UTC](https://forums.freertos.org/t/arm-under-c-c/5305/6 "2006-02-20T08:51:58Z")
**[jra01](https://sourceforge.net/u/jra01/)** wrote on [Monday, February 20, 2006](https://sourceforge.net/p/freertos/discussion/382005/thread/ea716e73/#cd3f/2a31): I also experienced in one environment, that when I set it up for c++ all the \*.c files were omitted, and not included in the make. Jokke again