CODEWITHSUNDEEP
arrayschar
Abhilash
Abhilash

Reputation: 3

Getting the size of the char* array passed as an input to C++ function

I am trying to pass a character pointer array as an input from C test driver to C++ function (available in C wrapper)

char* LowerList[10];
LowerList[0]="abc";
LowerList[1]="def";
LowerList[2]="hij";

When available on the C++ side the values displayed for the the element is displayed as 

char* LowerList[0]="abc";
LowerList[1]="def";
LowerList[2]="hij";
LowerList[3]=ƒì¶S<\$ UV<35?Ä@
LowerList[34]=ƒ<bad pointer>

I need to get the size of the array passed on to the C++ size which I could have got using while (LowerList[count]) but unable to do so because of the junk value. Please let me know if any way I can find the correct size of the char* LowerList[] by initialising ,memory allocation or converting it to vector.

Corrected the above code for typo error

Here are my comments on some of the suggestions given to me so far:

1) Pass the size of the array as a parameter as well- A limitation for my scenario .2) Conversion to the vector need the size to be available 3) Sentinel value at which position I need to add . As stated earlier I am trying to handle a scenario where the user pass the value as 3 which leads to the failure.I don't have any control on restricting the way C user my C++ wrapper with his C test driver.

Upvotes: 0

Views: 381

Answers (2)

JAB
JAB

Reputation: 21089

The pointers LowerList[3] through LowerList[9] are all uninitialized, if I'm not mistaken. You could always just use NULL as a sentinel value, and either assign it explicitly or do something like this:

char* LowerList[10] = { "abc", "def", "hij" };

This should initialize the remaining pointers in the array to NULL.

In response to your second comment:

#define LOWER_LIST_SIZE 10
#define MINIMUM_SIZE 2

#if LOWER_LIST_SIZE < MINIMUM_SIZE
    #error "LOWER_LIST_SIZE must be >= MINIMUM_SIZE"
#endif

char *LowerList[LOWER_LIST_SIZE] = // etc.

Or something like that.

http://en.wikipedia.org/wiki/C_preprocessor#User-defined_compilation_errors_and_warnings

Upvotes: 1

BlackJack
BlackJack

Reputation: 2876

Furthermore, your initialization as given is totally wrong. You have:

char* LowerList[10]; 
char* LowerList[0]="abc"; 
char* LowerList[1]="def"; 
char* LowerList[2]="hij";

What you want is:

char* LowerList[10]; 
LowerList[0]="abc"; 
LowerList[1]="def"; 
LowerList[2]="hij";

or the alternative that JAB has. The issue with your version is that you are essentially declaring LowerList 4 times, but you can't do that.

Upvotes: 1

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