CODEWITHSUNDEEP
cglib
omninonsense
omninonsense

Reputation: 6892

How to access a GString pointed to by a gpointer from a GHashTable

The C code

#include <glib.h>
//...
GHashTable *hash = g_hash_table_new(NULL, NULL);
GString val;

g_hash_table_insert(hash, (int*)5, g_string_new("Bar"));
val = g_hash_table_lookup(hash, (int*)5); // line 10

printf("Foo ~ %s\n", val->str); // line 16

if (NULL == val) // line 18
    printf("Eet ees null!\n");

Which produced:

ctest.c:10: error: incompatible types in assignment

ctest.c:16: error: invalid type argument of '->' (have 'GString')

ctest.c:18: error: invalid operands to binary == (have 'void *' and 'GString')

What am I doing wrong? :(

EDIT: Some might be confused and ask ask themselves "Why didn't she use g_string_printf()?"

Because I need to access gchar *str, printing was just my way of "debugging" it.

EDIT: Added line 18, and commented the spazzing lines (yes, lots of whites-paces all over the place. I'm dreadful, I know).

Upvotes: 0

Views: 3612

Answers (3)

ouah
ouah

Reputation: 145899

A GString structure is declared as:

struct GString {
  gchar  *str;
  gsize len;
  gsize allocated_len;
};

so to access the string just use the . operator:

printf("%s\n", val.str)

Also passing (int*) 5 as an argument to your function is probably wrong. This converts the integer value 5 to a pointer. But what you want is a pointer to an int where the int value is 5.

To do this you can either use a compound literal: &(int) {5} or use a pointer to an object of type int:

int bla = 5;  // and you pass &bla as the argument of your function

Upvotes: 1

cnicutar
cnicutar

Reputation: 182664

The function g_string_new returns a GString *. So that's what's getting stored in the hash. And the function g_hash_table_lookup returns a void *. You likely want something like this:

GString *val;
val = g_hash_table_lookup(hash, (int*)5);
printf("Foo ~ %s\n", val->str);

Upvotes: 2

James M
James M

Reputation: 16718

val->str should be val.str - it's not a pointer. This also means you can't do if (NULL == val).

Upvotes: 0

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