hmdel compiler warning for -Wall

[jmcpheters]

I notice when my program uses hmdel, when compiled with -Wall, it has the the warning shown below that can be suppress by -Wno-unused-value. Is the warning shown below expected and OK? Below I've also included an example program, which appears to execute as expected.

Please advise.

Warning:

[ec2-user@ip-10-16-14-50 scratch]$ gcc -Wall -D_GNU_SOURCE -fPIC -DPIC  -o main main.c
In file included from main.c:4:
main.c: In function ‘main’:
stb_ds.h:587:153: warning: right-hand operand of comma expression has no effect [-Wunused-value]
  587 |     (((t) = stbds_hmdel_key_wrapper((t),sizeof *(t), (void*) STBDS_ADDRESSOF((t)->key, (k)), sizeof (t)->key, STBDS_OFFSETOF((t),key), STBDS_HM_BINARY)),(t)?stbds_temp((t)-1):0)
      |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
stb_ds.h:427:21: note: in expansion of macro ‘stbds_hmdel’
  427 | #define hmdel       stbds_hmdel
      |                     ^~~~~~~~~~~
main.c:38:9: note: in expansion of macro ‘hmdel’
   38 |         hmdel(Hash, &Mydata1);
      |         ^~~~~

An example program is:

// gcc -Wall -D_GNU_SOURCE -fPIC -DPIC -shared -ldl -o main main.c

#define STB_DS_IMPLEMENTATION
#include "stb_ds.h"

#include <stdio.h>

struct data1 {
        char label1[50];
        int metric1;
};

struct data2 {
        char label2[50];
        int metric2;
};

typedef struct data1 Data1;
typedef struct data2 Data2;

Data1 Mydata1 = { "forward", 2 };
Data2 Mydata2 = { "reverse", 3 };

struct { Data1 *key; Data2 *value; } *Hash;

int main(void) {
        Data2 *getdata = hmget(Hash, &Mydata1);
        if (!getdata) {
                hmput(Hash, &Mydata1, &Mydata2);
        }
        getdata = hmget(Hash, &Mydata1);
        if (!getdata) {
                printf("not working\n");
                return 1;
        }
        printf("label = %s, metric = %d\n", getdata->label2, getdata->metric2);
        hmdel(Hash, &Mydata1);
        return 0;
}

[nothings]

I think hmdel returns the deleted item if it was present, so you should just cast to (void) if you're not using its return value, same as any function.