Compilation fails when using multiple files

[gstaaij]

When using multiple C files, or when using the library as a separate translation unit ht.o, linking fails because the ht__* functions are static.

Example (multiple C files)

foo.h

#include "ht.h"

typedef Ht(const char*, int) Ht_Str_Int;

void foo(Ht_Str_Int* ht);

foo.c

#include "foo.h"

void foo(Ht_Str_Int* ht) {
    *ht_put(ht, "foo") = 69;
    *ht_put(ht, "bar") = 420;
    *ht_put(ht, "baz") = 1337;
}

main.c

#include <stdio.h>
#include "foo.h"

#define HT_IMPLEMENTATION
#include "ht.h"

int main() {
    Ht_Str_Int ht = {.hasheq = ht_cstr_hasheq};
    foo(&ht);
    *ht_put(&ht, "hello") = 37;
    ht_foreach(value, &ht) {
        printf("%s => %d\n", ht_key(&ht, value), *value);
    }
    ht_free(&ht);
    return 0;
}

When building the above files, I get:

$ cc -ggdb -o main main.c foo.c
In file included from foo.h:1,
                 from foo.c:1:
ht.h:512:14: warning: ‘ht__put’ used but never defined
  512 | static void *ht__put(Ht__Abstract *ht, void *key, Ht__Layout l);
      |              ^~~~~~~
/usr/bin/ld: /tmp/cc7sFE07.o: in function `foo':
/tmp/ht-test/foo.c:4:(.text+0xb4): undefined reference to `ht__put'
/usr/bin/ld: /tmp/ht-test/foo.c:5:(.text+0x142): undefined reference to `ht__put'
/usr/bin/ld: /tmp/ht-test/foo.c:6:(.text+0x1c4): undefined reference to `ht__put'
collect2: error: ld returned 1 exit status

Example (with ht.o)

Building the library beforehand using cc -DHT_IMPLEMENTATION -x c -c ht.h -o ht.o does not work at all.

main.c

(this is the example from the readme)

#include <stdio.h>
#include "ht.h"

int main(void) {
    Ht(const char *, int) ht = {
        .hasheq = ht_cstr_hasheq,
    };
    *ht_put(&ht, "foo") = 69;
    *ht_put(&ht, "bar") = 420;
    *ht_put(&ht, "baz") = 1337;
    ht_foreach(value, &ht) {
        printf("%s => %d\n", ht_key(&ht, value), *value);
    }
    ht_free(&ht);
    return 0;
}

$ cc -ggdb -o main main.c ht.o
In file included from main.c:2:
ht.h:512:14: warning: ‘ht__put’ used but never defined
  512 | static void *ht__put(Ht__Abstract *ht, void *key, Ht__Layout l);
      |              ^~~~~~~
ht.h:517:14: warning: ‘ht__key’ used but never defined
  517 | static void *ht__key(void *slot, Ht__Layout l);
      |              ^~~~~~~
ht.h:518:13: warning: ‘ht__next’ used but never defined
  518 | static bool ht__next(Ht__Abstract *ht, void **slot, Ht__Layout l);
      |             ^~~~~~~~
ht.h:520:13: warning: ‘ht__free’ used but never defined
  520 | static void ht__free(Ht__Abstract *ht);
      |             ^~~~~~~~
/usr/bin/ld: /tmp/ccJ394r5.o: in function `main':
/tmp/ht-test/separate/main.c:8:(.text+0xc7): undefined reference to `ht__put'
/usr/bin/ld: /tmp/ht-test/separate/main.c:9:(.text+0x164): undefined reference to `ht__put'
/usr/bin/ld: /tmp/ht-test/separate/main.c:10:(.text+0x201): undefined reference to `ht__put'
/usr/bin/ld: /tmp/ht-test/separate/main.c:12:(.text+0x29a): undefined reference to `ht__key'
/usr/bin/ld: /tmp/ht-test/separate/main.c:11:(.text+0x346): undefined reference to `ht__next'
/usr/bin/ld: /tmp/ht-test/separate/main.c:14:(.text+0x35e): undefined reference to `ht__free'
collect2: error: ld returned 1 exit status

[bennyyip]

Since ht_put is a macro and it reference ht__put, ht__put cannot be static.
Maybe we need to add something like

#ifndef STBIDEF
#ifdef STB_IMAGE_STATIC
#define STBIDEF static
#else
#define STBIDEF extern
#endif
#endif

@rexim

[NikitaMingazov]

yeah I don't know why the functions are static rather than just putting the implementation ifndef inside of the header ifndef like this:

#endif // HT_IMPLEMENTATION

#endif // HT_H_

that and removing static fixes both problems

[nikita-edel]

well thats the problem with this hashmap
every instance of an include, if you compile with that define, every source file will pull the implementation regardless of ordering of the headers
removing static will just cause redifinition errors regardless, if you define globally

the solution is to have multiple header guards

• for common types like the enums and typedefs so you dont get an redefinition for them
• the macros that will be needed, but not used in headers
• define IMPLEMENTATION only in source files
• or like ... have multiple files for the declaration and implementation so you have external linkage...