Teknikal-Notes

Hi have this code

Expand|Select|Wrap|Line Numbers

 struct SF {
 
  std::string mnemonic;//mnemonic that represents it
  std::string name;//a descriptive name
  ushort num_val1;// number of the first value
  uchar possiblevalues_num; //number of the possible values.
  uchar type; /*  = 1 if the feature is utilized in the models*/
};

basically i am trying to declare a std::string object in a struct to later fill it with information

the next step i allocate an array of SF structs and try to do it

Expand|Select|Wrap|Line Numbers

 SF * FTab;
  FTab = (SF *) calloc(6, sizeof(SF));
 
 
  FTab[0].num_val1 = (ushort) 5;
  FTab[0].mnemonic("xpto");

the ushort type i can acess, the std::string generates a segmentation fault error, and i can't understant why. Does anyone know what i am doing wrong?

PS- sorry for the bad english.

weaknessforcats

It's the call to calloc.

C++ uses constructors and destructors to initialize and clean up objects. calloc doesn't know about this so never called them. Your string members are garbage.

Do not use C memory allocation in C++.

Use only new an delete. Here is the corrected code:

Expand|Select|Wrap|Line Numbers

struct SF {
 
  std::string mnemonic;//mnemonic that represents it
  std::string name;//a descriptive name
  unsigned short num_val1;// number of the first value
  unsigned char possiblevalues_num; //number of the possible values.
  unsigned char type; /*  = 1 if the feature is utilized in the models*/
};
 
int main()
{
SF * FTab;
  FTab = new SF[5];
 
  FTab[0].num_val1 = 5;
  FTab[0].mnemonic ="xpto";
}
 

Decide now whether you will write in C++ or not. If yes, then do not:
1) malloc, calloc, alloc, etc.....
2) memcpy, mem... anything
3) free
4) exit(1)
5) strcpy, str... anything

for openers.

Teknikal-Notes

Pages

iperf for linux

The Cauchy-Schwarz Master Class: An Introduction to the Art of Mathematical Inequalities (Maa Problem Books Series.)

Eclipse Rich Client Platform (2nd Edition)

TANDEM

Upstream và Downstream là gì ?

Tính toán Mbps

Instructions

mathhoang - vietnam_hoangminhnguyen: [Ebook]Chuyên đề bất đẳng thức

[Ebook]Chuyên đề bất đẳng thức

How Chinese learn mathematics

std::string as struct member variable

re: std::string as struct member variable