Tips and Tricks (2)
For those, like myself, who come from the VB world, pointers have been a scarecrow for long and refrained the good willing volunteer from getting into the world of C… This tip deals with functions returning a string.
Say that you want to return a string from a function (returnZ) that will be passed to an other function/command, kind of:
char* returnZ() {
char vResult[2]; // Declare vector of characters
vResult[0] = 'Z'; // Fill in vector
vResult[1] = '�'; // Do not forget the EOS character
return vResult; // Return pointer to vector
}
This will not work!
The reason being that the function will in fact return a pointer to the vector of characters. And this vector, for which some memory has been allocated during execution of the function code, has been released to… I do not know, after completion of the function code.
There are a couple of turnaround solutions, among which the next exemples:
char* returnZ() {
char static vResult[2]; // Declare static vector of characters
vResult[0] = 'Z'; // Fill in vector
vResult[1] = '�'; // Do not forget the EOS character
return (vResult); // Return pointer to vector
}
In this exemple, the vector is declared as static so that it remains after the execution of the function. Draw back: some memory keeps allocated to the vector.
char* returnZ(char vResult[]) {
vResult[0] = 'Z'; // Fill in vector
vResult[1] = '�'; // Do not forget the EOS character
return (vResult); // Return pointer to vector
}
In this exemple, the vector is passed to the function from the calling function/command.