Problem using an array inside a switch statement

Question

I am having a problem when using a switch statement to check for something inside an array. I am using an int as my switch, then I compare the character arrays using strstr. So it reads like this:

void function(char *buffer, uint32_t size){
  char *p=(char*)malloc(compareSize); //compareSize is the size of the text to be compared
  #define TXTCOMPARE1 (char*)"Sample Text 1"
  #define TXTCOMPARE2 (char*)"Sample Text 2"
  #define TXTCOMPARE3 (char*)"Sample Text 3"
  switch(intCompare){
    case COMPARE1 :
      p = strstr(buffer,TXTCOMPARE1); break;
    case COMPARE2 :
      p = strstr(buffer,TXTCOMPARE2); break;
    case COMPARE3 :
      p = strstr(buffer,TXTCOMPARE3); break;
  }
  if(p!=NULL) { Serial.println("Success!"); }
  else { Serial.println("No match"); }
    memset(&p,0,sizeof(p);
}

This method does not work and p is always NULL. However, when I write it out without the switch() it compares just fine:

//using the same p declaration as above
p = strstr(buffer,TXTCOMPARE1);
if(p != NULL) { Serial.print("Success:"); }
else { Serial.print("No Match"); }

Why would the switch statement give me different results for what is basically the same function call?

Edit: Actually it seems to break everywhere when I set more than one call to p = strstr(...). When there is only one strstr it works, when two or more are used, it does not...

Answer 1

One big problem is that you forgot the break statements for those cases. So if it compares in the first one and finds it, you'll still get null because it is going to go look for the third one afterwards.

Answer 2

I solved this problem, there were a few problems with the code that I found, so thanks for your comments. Basically, it lies in the #define# statements. First, in Arduino it's not such great practice to use #define for strings/chars, only for int. This is because the compiler applies the text every time they appear in the code, so it uses up a lot more memory. The problem here is solved by using static char TXTCOMPARE1 = {"Sample Text 1"};

Another problem was that there was no NULL terminated character at the end of the #define statement, so the program kept looking to the end of the stack when using strstr() and finding no termination, I think I was just getting lucky that it worked occasionally at all.

Furthermore, there is no need to clear p using memset. It needs to be declared as NULL and then reset after the switch by if(p){p = NULL;}.

And now it works!