UTHash in function call does iteration once but not second time - c

Question

I am having some issues with usage of a uthash on a local variable.
My code looks something like this, query_dict is a local variable uthash:
main functions:
query* query_dict = NULL;
split_query_into_terms(querystr, &query_dict);
print_query_struct(&query_dict);
prefetch_tokens(&query_dict);
more closely:
void prefetch_tokens(query** query_dict) {
query* entry;
for(entry=*query_dict; entry != NULL; entry=entry->hh.next) {
handle_token(entry->term);
}
}
void add_term_to_query(query** query_dict, char* term, dictionary_entry* dict_entry) {
// if query in hashtable, increase score:
query* myq = NULL;
if(*query_dict != NULL)
HASH_FIND_STR(*query_dict, term, myq);
if(myq == NULL) {
myq = init_alloc_query(term);
myq->dict_entry = dict_entry;
HASH_ADD_KEYPTR(hh, *query_dict, myq->term, strlen(myq->term), myq);
} else {
myq->score += 1.0f;
}
}
void split_query_into_terms(char* querystr, query** query_dict) {
char* myquery = strdup(querystr);
char* reentrant_saver;
char* token;
token = strtok_r(myquery, " \n", &reentrant_saver);
while(token != NULL) {
dictionary_entry* dict_entry = find_dict_entry(token);
if(dict_entry) {
add_term_to_query(query_dict, token, dict_entry);
}
token = strtok_r(NULL, " \n", &reentrant_saver);
}
}
void print_query_struct(query** query_dict) {
query* entry;
for(entry=*query_dict; entry != NULL; entry=entry->hh.next) {
fprintf(stdout, "%s: %f\n", entry->term, entry->score);
}
}
The call to print_query_struct runs fine, but the call to prefetch tokens, does one iteration, then crashes with:
Program received signal EXC_BAD_ACCESS, Could not access memory.
Reason: KERN_INVALID_ADDRESS at address: 0x0000001000000000
0x0000000100004959 in prefetch_tokens (query_dict=0x7fff5fbffa30) at search/c_port/search.c:241
241 handle_token(entry->term);
(gdb) bt
0 0x0000000100004959 in prefetch_tokens (query_dict=0x7fff5fbffa30) at search/search.c:241
1 0x00000001000049d2 in search (querystr=0x7fff5fbffbe5 "wash") at search/search.c:255
2 0x0000000100004a20 in main (argc=2, argv=0x7fff5fbffa80) at search/search.c:263
the address, 0x0000001000000000 always being the same.
I have been trying all kinds of different things, but could not get it working.
Does anyone here know what's going on?
structs:
typedef struct {
char* word;
uint32_t byte_offset;
uint32_t occurences;
uint32_t occurences_abstract;
postings_entry* posting;
UT_hash_handle hh; /* makes this structure hashable */
} dictionary_entry;
/* query has a number of terms (strings) */
typedef struct {
char* term;
float score;
dictionary_entry* dict_entry;
UT_hash_handle hh;
} query;
Edit:
I have simplified the code quite a bit and made a smaller runnable example, but in essence, this is the code that fails: http://pastebin.com/qdDiQMG0
compile, then run with ./binary
eg. ./binary "wash help"
Edit 2:
Solved it even though I do not quite understand why it worked:
rewrote the init_alloc_query from:
query* init_alloc_query() {
query* query = malloc(sizeof(query));
query->term = NULL;
return query;
}
to work like this:
void init_alloc_query(query** q) {
*q = malloc(sizeof(query));
(*q)->term = NULL;
}
And everything runs fine.

Answer 1

Solved it even though I do not quite understand why it worked: rewrote the init_alloc_query from:
query* init_alloc_query() {
query* query = malloc(sizeof(query));
query->term = NULL;
return query;
}
to work like this:
void init_alloc_query(query** q) {
*q = malloc(sizeof(query));
(*q)->term = NULL;
}
And everything runs fine.