UTHash in function call does iteration once but not second time

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.

I have simplified the code quite a bit, but in essence, this is the code that fails: http://pastebin.com/qdDiQMG0 compile, then run with ./binary eg. ./binary "wash help" — Eivind, Sep 25 '13 at 16:15
I looked at the code you posted. `myq` seems to be corrupt after the "call" to `HASH_ADD_KEYPTR`. No idea why yet. — Adam Burry, Sep 26 '13 at 04:43
I see now, it is indeed corrupted right after the macro has run. Not sure if it's my code, or could it be a uthash bug? — Eivind, Sep 30 '13 at 20:05

score 1 · Accepted Answer · answered Oct 02 '13 at 08:42

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.

UTHash in function call does iteration once but not second time

1 Answers1