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Closed 9 years ago.
I was wondering if casting here is the best solution:
This is the function prototype:
void function(unsigned char * data)
This is how I intend to use it (nSize is read from):
unsigned int nSize = 15;
function( (unsigned char*) &nSize);
Assuming the function prototype is set in stone and nSize has to be an int, yes that looks right to me.
Yes, in your case, cast seems necessary.
Note that using C++-style named cast is preferred than the C-style cast. In your case, reinterpret_cast is the right choice. Note that this is a dangerous behavior, see here for detail.
function(reinterpret_cast<unsigned char*>&nSize);
Related
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Closed 9 years ago.
Do I need to provide == and/or != operators? I've read here: Why don't C++ compilers define operator== and operator!=? that I do but when I actually tried it (didn't provide them and tried to use them) the program compiled fine. So what's going on?
Using VS2010 if it matters.
These operators are defined for fundamental, language-defined types, not for your custom ones. So it will work for ints, for example. But won't for class foo; unless you provide them explicitly - compiler doesn't know how to compare your own defined types if you haven't told it how to do it.
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Closed 10 years ago.
if((kulax>=schodki[i][0][0] && kulax<=schodki[i][1]][0]) && (kulay==schodki[i][2][0]+10))
spoczywa=true;
Hi guys, I have an array of integers which name is schodki and it is declared as int schodki[5][3][1] and the global variables : int kulax and int kulay.
What's wrong in the line of code which is above ?
EDIT : Of course. "i" is the value from current state of loop.
You have an extra ] in
kulax<=schodki[i][1]][0]
which probably screws up parsing and results in a confusing error message. The compiler probably sees it as
kulax<=schodki[i][1]
which is indeed an attempt to compare an integer to a pointer. Try to pay attention to your own code and make sure it is free from primitive syntax errors before asking questions here.
Other than that, there's nothing wrong with your code (assuming that the variables are really declared the way you say they are)].
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Closed 10 years ago.
I've seen a pretty strange (for me) usage of this method:
strncpy(somePointer,"%d",someInt);
What does this actually do? The integer specifier "%d" as the source is troublesome for me to understand.
It does what it says on the tin: It copies the literal string "%d" into a char buffer pointed to by somePointer, or at least the first someInt bytes of it (up to three).
Don't be upset by a percentage sign, it's just another character...
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Closed 10 years ago.
I am reading book "Thinking in C++" Bruce Eckel. The Chapter 3 in page 164(Polish edition)is about pointer to function.
Examples from the book:
void * (*(*fp1)(int))[10]
float (*(*fp2)(int,int,float))(int)
double (*(*(*fp3)())[10])()
int (*(*f4())[10])()
Can you tell me how I should interpret this and what is created by these examples because I do not understand the book solution?
I hope this tricky rule will help you to unwind such conundrums:
http://c-faq.com/decl/spiral.anderson.html
Let's take 4: int (*(*f4())[10])()
It reads f4 evaluated (f4()) and then dereferenced ((*f4())) can be subscribed ((*f4())[10]) then dereferenced ((*(*f4())[10])) and evaluated to give an int (int (*(*f4())[10])()).
It is thus a function returning a pointer of arrays to pointers of functions returning int.
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Closed 11 years ago.
Somebody told me that this piece of code has some serious issues but I have not been able to get my head around such issues. Can you guys please educate me on this?
static char BASED_CODE szFilter[] = "HTML Files (*.xls)|*.xls|All Files (*.*)|*.*||";
const char* filter = "HTML Files (*.xlsx)|*.xlsx|All Files (*.*)|*.*||";
size_t length = strlen(filter);
strcpy_s(szFilter, length + 1, filter);
Well, the buffer overrun leaps out at me – szFilter isn't big enough to receive filter.
Why not use std::string since you are using C++? That makes these issues vanish.
The second parameter of strcpy_s() should be the size of the destination buffer; you've given it the size of the input string.
But as you're working in C++, you should avoid strcpy() (etc.) entirely, and use std::string.
szFilter is shorter than filter, so there is not enough place to copy filter to szFilter. You current code has undefined behaviour.