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Gaston
Gaston
Associate III
March 11, 2022
Question

C++ Project that creates C main file

  • March 11, 2022
  • 5 replies
  • 7090 views

Hi,

If I create a C++ STM32CubeIDE project the main generated file is a C file (main.c) and I have to rename this to main.cpp every time I update pinmux, drivers, etc in order to call C++ functions. I think it's not an usual workflow but could anyone confirm this?

gaston

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5 replies

KnarfB
KnarfB
Super User
March 11, 2022

Confirmed. You may add a BUG topic to this post if you like.

As a workaround, create your own .cpp files with a main_cpp() and call it from main() in a user code section.

hth

KnarfB

TDK
TDK
March 11, 2022

"C++ project" means it has the C++ compiler step in addition to assembly and C. As if, if you add *.cpp files, it will handle them appropriately. Not sure if creating main.c is a bug or intended here.

"If you feel a post has answered your question, please click ""Accept as Solution""."
Gaston
GastonAuthor
Associate III
March 12, 2022

I'm not sure if it's a bug or not but the MCUXpressoIDE works as expected. In this case If you create a C++ project the IDE generates a .cpp main file (MKE06Z4_Project.cpp). This is a natural workflow to me without doing workarounds.

0693W00000KcLyhQAF.pnggaston

Pavel A.
Pavel A.
March 12, 2022

Please be sure, this is not a bug.

TL;DR Most of the ST libraries called by cube-generated code are plain C so it is just natural that the main.c is also a plain C file.

Perhaps the choice of the filenames main.c/main.h was not far-sighted, but it's too late to change. Many people already are used to this and will be upset if they change it.

OTOH integration of this C code with c++ is very easy (by design of c++).

For example, you can name your "main" cpp file like in MCUXpresso: "your_Project.cpp", change there main() to cpp_main(), and be done with it.

Gaston
GastonAuthor
Associate III
March 13, 2022

In this case it may be more appropriate to speak of 'very' nice-to-have feature.

The MCUXpresso libraries are also written entirely in plain C and if you create an MCUXpresso project in C++ you can call them from main.cpp without limitations. On the other hand, if you create a C project you won't be able to call libraries/functions written in C++.

Basically, creating a project in C++ should allow calls to C/C++ functions/libraries from main.cpp while a project created in plain C (main.c) will only allow calls to library functions written in plain C. I think no one will feel upset about this.

Despite creating a C++ project the STM32CubeIDE only generates a plain main.c instead of main.cpp. This makes it impossible to call C++ functions/libraries from main.c. I would have no problem renaming the file once but if I do multiple pinmux/peripherals updates they all generate a main.c and this workflow is no longer efficient at all.

gaston

Pavel A.
Pavel A.
March 14, 2022

> In fact it is the opposite. Using extern C allows you to call C functions from C++.

And also declare C++ functions callable from C and global variables that can be referred from C.

Gaston
GastonAuthor
Associate III
March 14, 2022

I think we should better understand how this works:

https://www.geeksforgeeks.org/extern-c-in-c/

My suggestion is clear and I have also provided the case of MCUXpresso, an environment very similar to STM32Cube, which solves this issue easy and efficiently.

Please, any feedback from ST side?

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