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The following sample of code
...
#include <cstring>
#include <set>
constexpr int BUFFER_MAX_SIZE = 1024;
struct connection
{
...
char inputBuffer[BUFFER_MAX_SIZE];
char outputBuffer[BUFFER_MAX_SIZE];
};
int main(int argc, char **argv)
{
...
std::set<connection> clientConnections;
...
for (auto &clientConnection : clientConnections)
{
char buffer[BUFFER_MAX_SIZE];
...
strncat(clientConnection.inputBuffer, buffer, BUFFER_MAX_SIZE);
...
strncat(clientConnection.outputBuffer, buffer, BUFFER_MAX_SIZE);
...
}
}
causes the error that is in the title for both strncat() calls. I have no idea why does it happen because as you can see inputBuffer and outputBuffer members are NOT declared as constant. Besides before I have made some changes in the code it worked fine. Can something else affect on this?
I suppose those lines are enough but I could add more ones later if required.
Looks like you have the order of the source and destination buffers reversed in your call to strncat()
char * strncat ( char * destination, const char * source, size_t num );
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When I write a function like below and use it in main(), it doesn't work.
Why does this happen? (I am a beginner).
void addBst(char *name, char *num);
int main(void)
{
addBst("a", "b");
return 0;
}
In C++, a string literal is a const char[N] array, where N is the length of the string, including the null terminator.
Since C++11, it is illegal to assign a string literal to a non-const char* pointer, as your code is doing. You need to use a const char* pointer instead, eg:
void addBst(const char *name, const char *num);
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How to copy char * to an array of 16 bytes.
const char *SK = "1234456789999978";
sample_aes_gcm_128bit_key_t alice[16];
memcpy(alice, (sample_aes_gcm_128bit_key_t*)SK, 16); //gives error
Definition of sample_aes_gcm_128bit_key_t
typedef uint8_t sample_aes_gcm_128bit_key_t[16];
Error:
error: expected constructor, destructor, or type conversion before ‘(’ token
memcpy(alice, (sample_aes_gcm_128bit_key_t*)SK, 16);
This works for me:
#include <iostream>
#include <cstring>
int main()
{
typedef int sgx_aes_gcm_128bit_key_t;
const char *SK = "1234456789999978";
sgx_aes_gcm_128bit_key_t alice[16];
std::copy(SK, SK + strlen(SK), alice);
for(auto& i : alice){
std::cout << i - '0';
}
return 0;
}
Take care that your typedef name matches the name you use. (It didn't in question.) And you can remove the cast to sgx_aes_gcm_128bit_key_t. Hopefully this accomplishes what you're trying to do.
If you want to use memcpy with C++, that is fully possible. Inside memcpy you should use casts to (void*)
memcpy((void*)alice, (void*)SK, 16);
Make sure to get types and size right to prevent segmentation fault.
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I'm studing about c++ semantics and syntax, I really don't know what is the problem with this code, it compile but stop working. I will apreciate your help, thanks.
#include <iostream>
#include <string.h>
using namespace std;
char* func(char* M)
{
int initval = 2;
char *x= new char[10];
x="idea";
strcpy(x, M+initval);
return x;
}
int main()
{
char* x;
char s[10]= "alguna";
x= func(s);
cout << *x << endl;
return 0;
}
Before this is closed, the x="idea"; is where your problem lies. You throw away your buffer and point it to a constant value, then try to assign to it, which almost always is illegal (should always be illegal, but apparently it is compiling for you...).
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I'm trying to find a way to convert an int to char of the corresponding value of the int (assuming int is one digit). (example 1='1' 5='5' 9='9') I've tried
int a=5;
char b=char(a+48);
whenever I try to run this the program crashes. How can I set up a system that works correctly?
It can be done using the following code:
char c = (char)(48 + a);
You can also use the '0' char value, instead of 48. It will improve code readability and let you not remember the value 48:
int a = 5;
char c = (char)((int)'0' + a);
As mentioned in comments, you can do this without explicit casts:
char c = '0' + a;
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Closed 9 years ago.
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How can I reinterpret cast from double to char* (I need it to store the data of double in file in bytes). Below is the code and I don't know why it doesn't work:
#include <iostream>
int main(int argc, char **argv)
{
const double tmpDouble = 1234.;
char *tmpChar = reinterpret_cast<char*>(tmpDouble);
return 0;
}
If what you had there worked, it probably wouldn't be what you want - the pointer's value would just be 1234 - effectively pointing to that address which might contain anything (not that it's accessible).
If you just want to have the double in binary format, you could do
const byte* pDouble = reinterpret_cast<const byte*>(&tmpDouble);
// |
// note the address here
But first check whatever it is you're using to write to file for a function prototype that takes a double directly.