Re: vector has segfault null dereference
* andrey.vul@gmail.com:
On Oct 1, 11:49 pm, "Alf P. Steinbach" <al...@start.no> wrote:
* andrey....@gmail.com:
On Oct 1, 9:31 pm, andrey....@gmail.com wrote:
On Oct 1, 8:01 pm, "Alf P. Steinbach" <al...@start.no> wrote:
...
//get all available options for value val
vector<u8> *options(u16 val) {
vector<u8> *cc = new vector<u8>();
According to my debugging, ^this^ line is throwing std::bad_alloc due
to a null pointer being returned from malloc. What is weird is that I
am allocating only 1 vector and I have 1 GB of ram so why is malloc
returning null?
Call trace:
[OS-dependent stuff]
C++ library!malloc()
C++ library!operator new()
sudoku![std::vector allocate]
sudoku!std::vector::insert
sudoku!std::vector::push_back
sudoku!solver::options
...
sudoku!main
...
u8 i;
//find and add avialbale numbers
for (i = 0; i < 9; ++i)
if (((1 << i) & val) == 0)
cc->push_back(i + 1);
return cc;
}
...
You have an infinite recursion in your search() function.
But the code has many other problems.
I suggest you start instead with removing all gotos, all raw arrays, all
calls to calloc and malloc and so on. One way to do that, which is what
I would prefer, is to copy your existing code to a backup (to look at),
than delete all contents of your file and start from scratch with an
empty main(). Remember to give yourself an electric shock every time
you even /think/ about reaching for goto or raw array or the like... :-)
The same thing happened when I tried to optimize my java code.
Well, C++ may be a powerful language, but translating from Java to C++
does not automatically fix algorithmic problems.
How did
you catch the infinite recursion and
An old dog may not have as keen a sense of smell, nor as acute hearing,
as a younger dog. But the older dog has some experience that largely
weights up for that (younger dogs generally refuse to believe that
unless the older dog keeps them well in line, biting them a little when
they get too focused on following their own dangerous whims, and this is
a problem for the older dogs believing in freedom and creativity). On
the other hand, it's difficult to teach an old dog to stop barking.
> do you know of a free static code
> analyzer that can find infinite recursion?
A good compiler can detect obvious infinite recursion. Less obvious
infinite recursion is in principle impossible to detect. Read up on the
halting problem.
Also, the java code used a raw array just fine.
Java has no such thing as a raw array.
Arrays in Java are dynamically type checked.
Cheers, & hth.,
- Alf
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