Identify User Defined Function and Library Defined Function

Question

I'm given a task to write a program that checks a piece of code, maximum of 20 lines of code, when the program runs you type in a function name, number of lines of code and type in the codes.

It's meant to search in the code and return if the function name you entered is a Library Function or User Defined Function or No Function if it doesn't find it, the code I've written is below, it doesn't work because I made mistakes and I've been trying to fix it but can't seem to figure it out, and I tried debugging to see where I made mistake, and I figured that in the function SearchRealisation it returns an error that

Run-Time Check Failure #2 - Stack around the variable 'buff' was corrupted.

This program sample returns Library function instead of user defined function

type the function name: addition
Get count string in code: 9
int addition(int num1, int num2)
{
int result = num1 + num2; //trial
return result;
}
int main()
{
addition(8, 9);
}

Output is Library Function but correct output should be User Defined Function since it was defined in the code

void InputText(int length, char Text[MAX_STRINGS][MAX_COLUMNS])
{
    //Repeat by Count String
    gets_s(Text[0]);
    for (int i = 0; i < length; i++)
        gets_s(Text[i]);
    //Output a string (starting with � zero and ending with Count String-1)
}
void OutMesseg(int param)
{
    //Display one of three messages according to the parameter
    if (param == -2)
        printf("%s", "user defined function");
    else if (param == -1)
        printf("%s", "no function");
    else
        printf("%s", "library function");
}

char* DeleteComentsInString(char Text[MAX_STRINGS], char New[MAX_STRINGS])
{
    char* a = strstr(Text, "//");
    int len = strlen(Text);

    if (a != NULL) len -= strlen(a);

    strncpy(New, Text, len);
    New[len] = '\0';
    return New;
}

bool IsTypeC(char Word[MAX_STRINGS])
{
    char ctype[6][MAX_STRINGS] =
    {

                         "int",
                         "bool",
                         "char",
                         "float",
                         "double",
                         "void"
    };

    for (int i = 0; i < 6; i++)
    {
        if (strstr(Word, ctype[i]) != 0)
            return true;
    }

    return false;
}

int SearchRealisation(int length, char Text[MAX_STRINGS][MAX_COLUMNS], int index_fanc, int& end)
{
    int count = 0;
    int start = -1;
    end = -1;
    char buff[MAX_STRINGS];
    //Find first {
    for (int i = index_fanc + 1; i < length && !count; i++)
    {
        if (strstr(DeleteComentsInString(Text[i], buff), "{") != NULL)
        {
            count++;
            start = i;
        }
    }

    //find last }
    for (int i = start + 1; i < length && count; i++)
    {
        if (strstr(DeleteComentsInString(Text[i], buff), "{") != NULL)
            count++;
        else if (strstr(DeleteComentsInString(Text[i], buff), "}") != NULL)
            count--;
        if (!count)
            end = i;
    }

    if (end == -1)
        start = -1;
    else
    return start;
}


int SearchFunction(int length, char Text[MAX_STRINGS][MAX_COLUMNS], char FunctionName[MAX_COLUMNS], int& end)
 {
    //bool flag = false;
    char commentDel[120];
    int in;

    for (int i = 0;  i < length; ++i)
    {
        DeleteComentsInString(Text[i], commentDel);
        if (strstr(commentDel, FunctionName) != NULL)
        {
            in = strlen(commentDel) - strlen(strstr(commentDel, FunctionName));

            if ((in == 0 || (in != 0 && commentDel[in - 1] == ' ')) && (commentDel[in + strlen(FunctionName)] == ' ' || commentDel[in + strlen(FunctionName)] == '(') && strstr(commentDel, ";") == NULL)
            {
                return SearchRealisation(length, Text, i, end);
            }
        }
    }

    end = -1;
    return -1;
}

int SearchResult(int length, char Text[MAX_STRINGS][MAX_COLUMNS], char FunctionName[MAX_COLUMNS])
{
    int index;
    int end;
    int start = SearchFunction(length, Text, FunctionName, end);

    if (start == -1)
        return -1;

    index = SearchFunction(length, Text, FunctionName, end);

    if (index < 0)
        return -2;

    return index;
}

int findFunction(char string[MAX_STRINGS][MAX_COLUMNS], char* functName, int M)
{
    return 0;
}

int main()
{
    int length = 0;
    char Code[MAX_STRINGS][MAX_COLUMNS] = { 0 };
    char FunctionName[MAX_COLUMNS];
    //char ConstantName[MAX_STRINGS];

    printf("type the function name: ");
    scanf("%s", &FunctionName);


    printf("Get count string in code: ");
    scanf("%d", &length);

    InputText(length, Code);

    printf("\n");

    OutMesseg(SearchResult(length, Code, FunctionName));
    return 0;
}

Answer 1

Thanks a lot to everyone that answered I came up with a way to search the code for function definition and thereby return a value if its defined or not, or not even found, might not be the best solution to the task but works so far

Answer 2

Well, you have been given a very difficult task:

There's no way to check this, as functions are resolved by a dynamic process that depends on your filesystem state, which is not available at runtime, after you have already compiled your program.

How do you distinguish a function that is compiled in a separate (but user defined) compilation unit from a system defined function? (e.g. double log(double);) that is defined in a math library? There is no way: the linker gets both from a different place (in the first case it gets it from the place you compiled the separate module, in the system case it gets it from a common library directory that has all the system related functions), but you don't have that information available at runtime).

In order to do this task feasible, you'd at least have the full set of source code files of your program. Preprocess them with the cpp(1) preprocessor (so you bypass all the macro expansion invocations) and then check for all function calls in the source code that are not provided in the full set of sources you have. This is quite similar to what the linker does. After compilation, the compiler leaves an object file with the compiled code, and a symbol table that identifies all the unresolved identifiers, and more important all the provided identifiers from this module. The linker then goes on all your modules trying to solve the unknowns, and for each that it doesn't have a solution in your code, it goes to the library directory to search for it. If it doesn't find it in either one, it fails telling you something is wrong.

In my opinion, you have been given a trap task, as the C language preprocess its input (this is something you should do, as many functions are hidden in the internals of macro bodies), then parse the code (for this, you need to write a C parser, which is no trivial task) to select which identifiers are defined in your code and which aren't. Finally you need to check all the calls you do in the code to divide the set in two groups, calls that are defined (and implemented) in your code, and calls that aren't (implemented, all the calls the compiler needs must be defined with some kind of prototype).

It's my opinion, but you have not a simple task, solvable in a short program (of perhaps one hundred lines) but a huge one.