Function dependencies not respected with --disable-main

[certik]

import_order_01.py:

from import_order_01b import f

@ccallback
def main1():
    a: i32 = f()
    print(a)

import_order_01b.py:

from lpython import i32

def f() -> i32:
    return 42

Compile using:

$ lpython -I. --show-c --disable-main import_order_01.py
...

// Implementations
void main1()
{
    int32_t a;
    a = f();
    printf("%d\n", a);
}

int32_t f()
{
    int32_t _lpython_return_variable;
    _lpython_return_variable = 42;
    return _lpython_return_variable;
}

This then fails to compile due to:

$ clang x.c                
x.c:41:9: error: implicit declaration of function 'f' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
    a = f();
        ^
1 error generated.

The issue is that main1 depends on f, but f gets generated below the function. It only happens when --disable-main is used, but we need to use it.

[certik]

I am not sure how to best test this in integration tests, due to the --disable-main. The @ccallback is needed, otherwise the function gets treated as unused.

[czgdp1807]

The --disable-main doesn't matter. Even without it, f() goes below main1,

...

// Implementations
void main1()
{
    int32_t a;
    a = f();
    printf("%d\n", a);
}

int32_t f()
{
    int32_t _lpython_return_variable;
    _lpython_return_variable = 42;
    return _lpython_return_variable;
}

int main(int argc, char* argv[])
{
    return 0;
}

[czgdp1807]

Its a problem with pass_wrap_global_stmts_into_program. It only shifts user defined functions into _global_symbols (generated module) only when they are called. In your case main1 is never called so it stays in the global scope. Now C backend first visits all the functions in global scope and since main1 lies in global scope so C code of it is generated first. Then f is generated when the modules are visited. If main1 is shifted to _global_symbols then it depends on import_order_01 and hence f will always be generated before main1 (which is correct).

End moral - So, IMO global scope should only contain intrinsic functions generated by libasr in intrinsic_function_registry.h. All user defined functions should be shifted to _global_symbols modules irrespective of the fact whether they are called by the user or not.