Running uPython script from C and calling C functions from the script

[empi91]

Hi, I didn't find anything similar enough in the old topics both here and on forum, so I decided to post a new one, hope that's ok

I have complex C application, where I want to add a functionality of executing external uPython scripts, but at the same time be able to call some defined C functions from this script during the execution.

So basically something like that:
C-based script component:

#include <...>

static  void python_print(char text)
static int python_getParameterValue(char paramID)
static int python_setParameterValue(int paramValue)

int main() {
	Py_Initialize();
	fp = _Py_fopen(file, "r");
	PyRun_SimpleFile(fp, file);
	Py_Finalize();
	return 0;
}

uPython script:

value1 = 10
text1 = "Hello from Python"
param1_ID = Module1.Name

python_print(text1)
python_getParameterValue(param1_ID)
python_setParameterValue(value1)

But while for a standard Python it seems relatively easy:

• add #include <python.h>
• link the python library to the C file
• somehow (I'm not there yet) make C functions visible for Python script (create Python modules from those C functions??)

then for uPython it seems more complicated and I got lost.
Here: Building MP as static library and here: Embedding MP as library in C read I have to make a library on my own

Here: Writing C modules there is something about writing modules in C, but I am unable to put it all together

The relatively easy way to do requires creating a .io library file from C file, which I am not very happy with (at least that's what I found) so every help, or just a proper direction will be much appreciated!

I did something similar using Lua and it's working, but now just trying to compare it with uPython

[dlech]

Did you look at https://github.com/micropython/micropython/tree/master/examples/embedding?

And this pull request hasn't been merged, but could be of interest.

[empi91]

Thank you very much for such an extensive answer!
Yes, I went through that example as well, but I think I unfortunately need more classical approach, with being able to execute file with uPython script from C code.

And therefore I think I have to once again ask for your help (hopefully the last time!):
After I fixed the error about lacking MICROPY_HW_BOARD_NAME definition, I'm trying to compile that project, but I got bunch of new errors, related to readline_hist this time:

../../shared/readline/readline.c: In function ‘readline_init0’:
../../shared/readline/readline.c:55:12: error: implicit declaration of function ‘MP_STATE_PORT’; did you mean ‘MP_STATE_MEM’? [-Werror=implicit-function-declaration]
     memset(MP_STATE_PORT(readline_hist), 0, MICROPY_READLINE_HISTORY_SIZE * sizeof(const char*));
            ^~~~~~~~~~~~~
            MP_STATE_MEM
../../shared/readline/readline.c:55:26: error: ‘readline_hist’ undeclared (first use in this function); did you mean ‘readline_init’?
     memset(MP_STATE_PORT(readline_hist), 0, MICROPY_READLINE_HISTORY_SIZE * sizeof(const char*));
                          ^~~~~~~~~~~~~
                          readline_init
../../shared/readline/readline.c:340:86: error: ‘readline_hist’ undeclared (first use in this function); did you mean ‘readline_t’?
 f (rl.hist_cur + 1 < MICROPY_READLINE_HISTORY_SIZE && MP_STATE_PORT(readline_hist)[rl.hist_cur + 1] != NULL) {
                                                                     ^~~~~~~~~~~~~
                                                                                      readline_t
../../shared/readline/readline.c:570:27: error: ‘readline_hist’ undeclared (first use in this function); did you mean ‘readline_t’?
         && (MP_STATE_PORT(readline_hist)[0] == NULL
                           ^~~~~~~~~~~~~
                           readline_t

And while it clearly stated that readline_hist, I have no idea where to declare it..

I found something about declaring it the following way:

#define MICROPY_PORT_ROOT_POINTERS \
    const char *readline_hist[8]; \

inside mpconfigport file (in case of the embedding example it's mpconfigport_minimal I guess, but it did not solve the problem..
And idea?

[jimmo]

This is a limitation of the embedding example... there's no way to define root pointers without the build process that makes MP_REGISTER_ROOT_POINTER work. I believe this is fixed in the approach in #9529

You must be looking at an older version of the repo if you're seeing MICROPY_PORT_ROOT_POINTERS.

Are you sure you need readline? This should only be necessary if you're enabling the REPL.

[empi91]

I don't think I need it actually, but when i removed it from the build, I got another error:

./build/libmicropython.a(pyexec.o): In function `pyexec_friendly_repl':
pyexec.c:(.text+0x47b): undefined reference to `readline'
pyexec.c:(.text+0x591): undefined reference to `readline'

So I guess it's required?

I'm working on the repo cloned directly from micropython github last week, so I don't think it is older version

[jimmo]

Assuming you're not calling pyexec_friendly_repl, then I think this is because you're calling pyexec_file, so you're getting everything else from pyexec.c (which includes pyexec_friendly_repl, which calls readline).

The simplest way to solve this is just to provide a dummy implementation of readline (somewhere in your .c code, e.g. the equivalent of hello-embed.c)

int readline(vstr_t *line, const char *prompt) {
    return 0;
}

I'm working on the repo cloned directly from micropython github last week, so I don't think it is older version

There is no occurrence of MICROPY_PORT_ROOT_POINTERS in the current revision of the master branch. Did you clone at v1.19.1 ?

[empi91]

Yes, 1.19.1
But I guess I was unclear -- I I found somewhere a topic where this info about MICROPY_PORT_ROOT_POINTERS was and just copied it together with const char *readline_hist[8]; \ to check if that would work. So it was not included in the repo after I clone it

Thanks for a tip about adding the dummy implementation, now it at least build up!

[empi91]

Hello again, another (newbie) question showed up:
What version (port?) of micropython is the mp_init() function using?
Because, as I have to add some custom C modules to my solution, I need to compile them using make USER_C_MODULES=../../../path/to/user/module, but I don't know which port to use for it.
I found the

    // call port specific initialization if any
    #ifdef MICROPY_PORT_INIT_FUNC
    MICROPY_PORT_INIT_FUNC;
    #endif

inside py/runtime.c but I am not sure how to use it properly

[dlech]

What version (port?) of micropython is the mp_init() function using?

It is used by all ports. Port-specific defines like MICROPY_PORT_INIT_FUNC are usually defined in mpconfigport.h.

[empi91]

Ok, but how do I ensure that the mp_init() called in C code in standalone program is using the same port I used to compile with the C module using make USER_C_MODULES=../../../?

And in which mpconfigport.h do I need to add MICROPY_PORT_INIT_FUNC?
As far as I understand, mpconfigport.h is related to some port (say Unix), while MICROPY_PORT_INIT_FUNC is related to mp_init() function I am calling in some standalone C program. I don't understand where the connection is

[dlech]

If you started with the embedding example, then there is a mpconfigport.h file there already.