Invoke assembly function in C++ code

Allen Lee

Hi,

I'm trying to invoke my assembly function(which is located in a .asm file) in the .cpp file.

But the build process report unresolved symbol error except I add extern "C"{} expression in the head and tail of the cpp file.

That means one can only call a assembly function directly in a C file.

What's the reason for that? I use CCS5.0.3 and CGToolsv7.2.1.

Allen

over 14 years ago

0 Archaeologist over 14 years ago

TI__Guru* 84285 points

C++ code can call assembly functions if they are declared with extern "C".

Are you using COFF or EABI? Make sure you use the right number of leading underscores when naming the assembly function, one for COFF and zero for EABI. Check for typos in the spelling of the function declaration and where it's called. Make sure you have a valid prototype for the assembly function in the CPP files or one of its headers, and make sure that prototype falls inside the extern "C" scope.

0 Allen Lee over 14 years ago in reply to Archaeologist

Genius 3770 points

Yes, I'm using EABI and there is no underscores before the name of asm function.

So you mean that there is only one way to call asm function within c++, by declaration of extern "C"?

0 Archaeologist over 14 years ago in reply to Allen Lee

TI__Guru* 84285 points

You can call assembly functions from C++ code without extern "C", but then you must mangle the function name in the assembly code, and it's almost never worth the trouble.

0 George Mock over 14 years ago in reply to Archaeologist

TI__Guru**** 251470 points

More background on this topic can be found in this wiki article.

Thanks and regards,

-George

0 Allen Lee over 14 years ago in reply to George Mock

Genius 3770 points

Thank you all, and choose extern"C" seems an effective way.

Code Composer Studio™︎

Code Composer Studio forum

Invoke assembly function in C++ code