lfind() and strcmp()

[patiobarbecue]

Dear there, I got inconsistent result on using lfind() and strcmp(), can anyone help me out? Thanks.

#include <stdlib.h>
#include <stdio.h>
#include <ctype.h>
#include <search.h>
#include <string.h>

int main(){
  char aName[250];
  aName[0]='O';aName[1]='H';aName[2]='\0';
  char **obj;
  obj = (char **)malloc(2*sizeof(char *));
  obj[0]= (char *)malloc(3*sizeof(char));
  obj[0][0]='O';
  obj[0][1]='H';
  obj[0][2]='\0';

int result1= strcmp(aName, obj[0]);
 fprintf(stdout, "%d\n",result1);
 if (result1==0) fprintf(stdout, "aName equals obj[0]\n");

  void *result2;
  size_t nelp=1;
  result2 = lfind((const void*)aName, (const void *)obj, &nelp, sizeof(char *), (int (*) (const void*, const void*))strcmp);

  if (result2==NULL) 
    fprintf(stdout, "aName:%s not found in obj[]\n", aName);
  else 
    fprintf(stdout, "found\n");

  int i;
  fprintf(stdout, "obj[] is:\n");
  for (i=0;i<nelp;i++)
    fprintf(stdout, "%s\t", obj[i]);
  fprintf(stdout, "\n");  fprintf(stdout, "\n");
}

[tabstop]

If you do

strcmp(aName, obj);

you won't get 0. The value of obj and the value of obj[0] are not the same.

[patiobarbecue]

I think lfind() will call strcmp() with "aName" and one of obj[0], obj[1], ...int turn. However the result is not what I wanted. Any suggection?

[tabstop]

I think lfind() will call strcmp() with "aName" and one of obj[0], obj[1], ...int turn.

You want that to happen. That has no real relation to the code you've written, however. Watch what happens during the calls:

#include <stdlib.h>
#include <stdio.h>
#include <ctype.h>
#include <search.h>
#include <string.h>

int tester_compare(const void* left, const void* right) {
    printf("Compare is seeing %p and %p\n", left, right);
    return strcmp(left, right);
}

int main(){
    char aName[250];
    aName[0]='O';aName[1]='H';aName[2]='\0';
    char **obj;
    obj = (char **)malloc(2*sizeof(char *));
    obj[0]= (char *)malloc(3*sizeof(char));
    obj[0][0]='O';
    obj[0][1]='H';
    obj[0][2]='\0';

    int result1= tester_compare(aName, obj[0]);
    void *result2;
    size_t nelp=1;
    result2 = lfind((const void*)aName, (const void *)obj, &nelp, sizeof(char *), tester_compare);

    if (result2==NULL)
        fprintf(stdout, "aName:%s not found in obj[]\n", aName);
    else
        fprintf(stdout, "found\n");
}

lfind assumes the thing you are searching is a block of memory -- but a 2D malloc'd fake array is not such a thing.