I'm trying to use the srand function, but I keep getting the error
"Called object of type 'int' is not a function or function pointer".
Here is how I'm using it:
srand(time(NULL));
Don't use the rand generator often, so I'm a bit lost.
I am sure you are using int srand as a variable somewhere in your code in the same scope where you are calling srand(time(NULL));
This clearly leads to an ambiguity.
Solution: Change the variable name.
Related
I'm getting assertions that don't make sense to me.
Code:
struct s {
int pred;
};
/*# assigns \result \from \nothing;
ensures \valid(\result);
*/
struct s *get(void);
int main(void)
{
return !get()->pred;
}
Frama-C output:
$ frama-c -val frama-ptr.c
[...]
frama-ptr.c:12:[kernel] warning: pointer comparison.
assert \pointer_comparable((void *)0, (void *)tmp->pred);
(tmp from get())
Am I doing something wrong or is it a bug in Frama-C?
This is not really a bug, although this behavior is not really satisfactory either. I recommend that you observe the analysis in the GUI (frama-c-gui -val frama-ptr.c), in particular the value of tmp->pred at line 12 in the Values tab.
Value before:
∈
{{ garbled mix of &{alloced_return_get}
(origin: Library function {c/ptrcmp.c:12}) }}
This is a very imprecise value, that has been generated because the return value of function get is a pointer. The Eva plugin generates a dummy variable (alloced_return_get), and fills it with dummy contents (garbled mix of &{alloced_return_get}). Even though the field pred is an integer, the analyzer assumes that (imprecise) pointers can also be present. This is why an alarm for pointer comparison is emitted.
There are at least two ways to avoid this:
use option -val-warn-undefined-pointer-comparison pointer, so that pointer comparison alarms are emitted only on comparisons involving lvalues with pointer type. The contents of the field pred will remain imprecise, though.
add a proper body to function get, possibly written using malloc, so that the field pred receives a more accurate value.
On a more general note, the Eva/Value plugin requires precise specifications for functions without a body; see section 7.2 of the manual. For functions that return pointers, you won't be able to write satisfactory specifications: you need to write allocates clauses, and those are currently not handled by Eva/Value. Thus, I suggest that you write a body for get.
I have a data structure looking like this:
QVector<QHash<QPair<int, int>, QVector<double> > > * wow = new QVector< QHash<QPair<int, int>, QVector<double> > >(4);
When i write wow->at(0).keys();
it works fine, but when i write wow[0].keys(); i receive an error saying the following :
'class QVector, QVector > >' has no
member named 'keys'
wow[0].keys();
^
I will need to use methods that require not only read-only access and i dont understand why this happens.Can you please help me and how should i access the Qhashe's methods in not a read only way?
When you write wow[0].keys(), with wow being a pointer, it returns the first object pointed to, like an array. It basically transforms into a dereference of the pointer, like this: wow->keys(). Since a QVector doesn't have a keys method, the compile fails.
If, instead, you want to get element 0 from your vector, you would either use wow->at(0).keys() or (*wow)[0].keys(). First dereference, then use the subscript operator.
I have found similar questions but none that worked for my situation, so I am asking my own.
I want to use a library function that takes a pointer to a std::vector, and fills it with data.
I already have a C++/CLI Wrapper set up.
I am currently trying to instantiate the vector in the wrapper,
private:
std::vector<int>* outputVector
and in the constructor, I instantiate it :
outputVector = new std::vector<int>();
Now, in the wrapper method that calls the c++ library function :
m_pUnmanagedTPRTreeClass->GetInRegion(..., &outputVector)
I omitted the other parameters because they dont matter for this case. I can already use other functions of the library and they work without a problem. I just can't manage to pass a pointer to a std::vector.
With the code like this, I get the error message :
error C2664: 'TPSimpleRTree<CT,T>::GetInRegion' : cannot convert parameter 3 from 'cli::interior_ptr<Type>' to 'std::vector<_Ty> &'
I have tried removing the "&", as I am not great at C++ and am unsure how to correctly use pointers. Then, the error becomes :
error C2664: 'TPSimpleRTree<CT,T>::GetInRegion' : cannot convert parameter 3 from 'std::vector<_Ty> *' to 'std::vector<_Ty> &'
EDIT: I have tried replacing "&" by "*", it does not work, I get the error :
cannot convert from 'std::vector<_Ty>' to 'std::vector<_Ty> &'
The signature of the c++ function for the vector is so :
GetInRegion(..., std::vector<T*>& a_objects)
Given the signature:
GetInRegion(..., std::vector<T*>& a_objects)
You would call this (in C++ or C++/CLI) like:
std::vector<int*> v;
m_pUnmanagedTPRTreeClass->GetInRegion(..., v);
Then you can manipulate the data as needed or marshall the data into a .Net container.
'std::vector<_Ty> *' to 'std::vector<_Ty> &'
is self explanatory, you need to dereference instead of taking a pointer, so instead of:
m_pUnmanagedTPRTreeClass->GetInRegion(..., &outputVector)
use:
m_pUnmanagedTPRTreeClass->GetInRegion(..., *outputVector)
^~~~~~~!!
after your edit I see your getinregion signature is:
GetInRegion(..., std::vector<T*>& a_objects)
so it accepts std::vector where T is a pointer, while you want to pass to getinregion a std::vector where int is not a pointer.
I'm trying to read some example code about implicit creation of QVariants from enum values.
About the following line of code:
QVariant::fromValue<Qt::PenStyle>(Qt::SolidLine)
I don't really understand what is the purpose of Qt::PenStyle in the above expression.
I think Qt::SolidLine is unique.
The syntax is OK?
Shouldn't it be something like:
QVariant::fromValue(Qt::SolidLine)
?
Sorry if this question seems dumb.
You can use this form:
1) QVariant::fromValue(Qt::SolidLine)
QVariant::fromValue(const T & value) is a template method. When you call a template method or function you can specify for what type of argument this method should be called. If you don't do that a compiler tries to do it for you. That is why 1) is equal to this:
2) QVariant::fromValue<Qt::PenStyle>(Qt::SolidLine)
But you can call this method for int and pass enum value (if you are not at c++11):
3) QVariant::fromValue<int>(Qt::SolidLine)
or even force creating of QPen:
4) QVariant::fromValue<QPen>(Qt::SolidLine)
EDIT:
If someone is suprised by 4 and want to know how it works: it is the same as if there was a method (actually it is created during the compilation):
QVariant::fromValue(const QPen& pen);
When you call this method with Qt::SolidLine compiler uses an implicit constructor QPen(Qt::PenStyle style) to create a new temporary QPen object and pass it as an argument to the method fromValue.
While working i met this annoying message
Strict Standards: Only variables should be passed by reference in G:\xampp\htdocs\MyProject\ZendSkeletonApplication\module\Admission\src\Admission\Controller\AdmissionController.php on line 107
My code
$consoldatedCities='';
array_walk_recursive($StateCityHash, function($cityName,$cityId) use(&$consoldatedCities){$consoldatedCities[$cityId] = $cityName; }); // line 107
This is to convert multidimensional array into simple array
But the code works as i expected.. can anyone tell me how to solve this problem
Here http://php.net/manual/en/language.references.pass.php it says that "There is no reference sign on a function call - only on function definitions." Try removing the '&' from your function call code there and see if that gets rid of the message.
---Edit---
Looking at this thread here "Strict Standards: Only variables should be passed by reference" error
you could try saving your callback function into a variable before passing it to the array walk function:
$consoldatedCities=array();
$callbackFcn=
function($cityName,$cityId) use(&$consoldatedCities)
{
$consoldatedCities[$cityId] = $cityName;
};
array_walk_recursive($StateCityHash, $callbackFcn);