Re: behavior of char* in a hash

"Jim Langston" <>
Thu, 13 Sep 2007 16:28:07 -0700
"digz" <> wrote in message

On Sep 12, 8:37 pm, digz <> wrote:

This is a simple case of a problem I am having with using char* in a
The code prints the size correctly( 3) and it should print three lines
of output but is printing only two. I do not want to reserve space for
the char* using new etc..( it will never will be deepcopied using
strcpy etc..) always holds an address.

I know I am making some very fundamental mistake what am I missing
here ?

using namespace std;
struct eqstr
     bool operator()(const char* s1, const char* s2) const
              return strcmp(s1, s2) == 0;


struct cacheType {
    int i;
    double d;
    char* c;


int main()
    typedef boost::hash<const char*> strHashFn;
    typedef __gnu_cxx::hash_map<const char*, cacheType, strHashFn,
eqstr> cacheMap;
    typedef cacheMap::const_iterator It;
    cacheMap cMap_;
    cacheType ci_, cd_, cc_;
    ci_.i = 1;
    cd_.d = 2.0;
    const char* c = "2007-09-11 18:00:00";
    cc_.c = const_cast<char*>(c);

    cMap_.insert(make_pair("A2", cc_));
    cMap_.insert(make_pair("A1", cd_));
    cMap_.insert(make_pair("A0", ci_));

    cout << cMap_.size() << std::endl;

    for( It i=cMap_.begin(); i != cMap_.end(); i++)
     cout << i->first << " " << (i->second).i << " " << (i->second).d
<< " "<
< (i->second).c << std::endl;


did I break some list etiquette ? is that why my question is not being

Most people, well me anyway, don't deal with hash maps. I know the theory
but have never found a real use for them, so never used them. To answer
your question I would have to compile your code, find out where the problem
is, then maybe have to research hash maps to be able to answer. And since
you're already using hash maps I fgiure you can do the research :D

This code does not seem to be the minimal code to reproduce the bug for a
quick analize, and if it is, then the subject is complicated which would
require even more time to research it and find the problem. If I had any
interest in ever using hash maps I'd probably take the time to figure out
what the problem is.

As it is, you did not break any list etiquette with this question. Some of
us just don't use boost and such. I don't even have boost installed to be
able to compile the code.

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