Calling C++ constructors at runtime init

Technical Note 16676






2018/5/31 9:14


The application runs into a random hardware fault if "Automatic runtime library selection" is disabled. (If the option is enabled, then is there no run-time error). 

Applies to

The project is built with any of the C++ dialects available in IAR Embedded Workbench for ARM version 6.x or newer.


When the project is linked with automatic selection of the IAR libraries, a call to the __iar_cstart_call_ctors method is added by the linker. See Project > Options > Linker > Library > "Automatic runtime library selection".

If the project is linked without the automatic library selection, the linker does not add a call to the __iar_cstart_call_ctors method.

Solution in IAR Embedded Workbench for ARM 6.10.2 and newer

Add a command line option at Project > Options > Linker > Extra Options. Enter this text:

--extra_init __iar_cstart_call_ctors the text box.

Solution in IAR Embedded Workbench for ARM 6.10.1 and older

In this/these version(s) the linker does not have the --extra_init command line option.
The recommendation is to make an explicit function call, for example early in the main() function.

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