c - strncpy issue
- by Joe
Hi there,
I am getting segmentation fault when using strncpy and (pointer-to-struct)-(member) notation:
I have simplified my code. I initialise a struct and set all of it's tokens to an empty string. Then a declare a pointer to a struct and assign the address of the struct to it.
I pass the pointer to a function. I can print out the contents of the struct at the beginning of the function, but if I try to use the tp - mnemonic in a strncpy function, I get seg fault. Can anyone tell me what I am doing wrong?
typedef struct tok {
char* label;
char* mnem;
char* operand;
}Tokens;
Tokens* tokenise(Tokens* tp, char* line) {
// This prints fine
printf("Print this - %s\n", tp -> mnem);
// This function gives me segmentation fault
strncpy(tp -> mnem, line, 4);
return tp;
}
int main() {
char* line = "This is a line";
Tokens tokens;
tokens.label = "";
tokens.mnem = "load";
tokens.operand = "";
Tokens* tp = &tokens;
tp = tokenise(tp, line);
return 0;
}
I have used printf statements to confirm that the code definitely stops executing at the strncpy function.
Can anyone tell me where I am going wrong?
Many thanks
Joe
