thinking of the namespace proposal for c, and, i wonder if, we couldn’t have namespaces done in the preprocessor, like:

/* lib.h */
#namespace lib lib_

void lib::foo(); /* declares lib_foo as a function name */

/* app.c */
#include <lib.h>
#using lib::foo
#using lib::foo as nya
#using lib as MyApi

int main(void) {
	/* all of those would be pre-processed to lib_foo() */
	lib::foo();
	foo();
	nya();
	MyApi::foo();
}

works with macros, and identifiers, basically anywhere a #define would also work

and could be backwards compatible, e.g. if i were to use it in openrc:

/* rc.h */
#ifdef _HAS_NAMESPACE
#namespace rc rc_
#namespace RC RC_
#endif

now older c programs can still use rc_service_resolve, and newer ones can use rc::service_resolve (as well as #using directives)

including whole namespace, like #using lib, could work but it’d be a pain to implement i think, since the preprocessor would need to keep track of all lib_ it sees since #namespace was declared, and forward-replace them

but with or without whole-namespace-inclusion, this has really simple semantics and imo predictable errors, as namespacing conflicts can be reported the same way “redefinition” of macro names are

#include <stdio.h>
int main()
{
#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
    puts("Little endian");
#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
    puts("Big endian");
#else 
    printf("ayo wtf %d\n", __BYTE_ORDER__);
#endif
    printf("%#b", 'twinspin6');
    return 0;
}

main.c: In function ‘main’:
main.c:12:19: warning: character constant too long for its type
   12 |     printf("%#b", 'twinspin6');
      |                   ^~~~~~~~~~~
Little endian
0b1110000011010010110111000110110