Why do I keep getting compiler errors with strtok in C? - c

Question

My assignment is to create a progrma that asks the users for a date then prints if its valid or not. I am only allowed to use strings and no int %d.
Why does my program get so many compiler errors dealing with the strtok and calling the function?
Severity Code Description Project File Line Suppression State
Warning C4024 'getInput': different types for formal and actual parameter 1 dating c:\users\chris\documents\visual studio 2015\projects\dating\dating.c 26
Warning C4047 'function': 'char *' differs in levels of indirection from 'char' dating c:\users\chris\documents\visual studio 2015\projects\dating\dating.c 26
Warning C4024 'getInput': different types for formal and actual parameter 2 dating c:\users\chris\documents\visual studio 2015\projects\dating\dating.c 26
Warning C4024 'getInput': different types for formal and actual parameter 3 dating c:\users\chris\documents\visual studio 2015\projects\dating\dating.c 26
Warning C4996 'scanf': This function or variable may be unsafe. Consider using scanf_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details. dating c:\users\chris\documents\visual studio 2015\projects\dating\dating.c 19
Warning C4996 'strtok': This function or variable may be unsafe. Consider using strtok_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details. dating c:\users\chris\documents\visual studio 2015\projects\dating\dating.c 21
Warning C4996 'strtok': This function or variable may be unsafe. Consider using strtok_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details. dating c:\users\chris\documents\visual studio 2015\projects\dating\dating.c 22
Warning C4996 'strtok': This function or variable may be unsafe. Consider using strtok_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details. dating c:\users\chris\documents\visual studio 2015\projects\dating\dating.c 24
Warning C4098 'getInput': 'void' function returning a value dating c:\users\chris\documents\visual studio 2015\projects\dating\dating.c 90
Warning C4477 'printf' : format string '%s' requires an argument of type 'char *', but variadic argument 1 has type 'int' dating c:\users\chris\documents\visual studio 2015\projects\dating\dating.c 47
Warning C4477 'printf' : format string '%s' requires an argument of type 'char *', but variadic argument 2 has type 'int' dating c:\users\chris\documents\visual studio 2015\projects\dating\dating.c 47
Warning C4477 'printf' : format string '%s' requires an argument of type 'char *', but variadic argument 3 has type 'int' dating c:\users\chris\documents\visual studio 2015\projects\dating\dating.c 47
Error LNK2019 unresolved external symbol _WinMain#16 referenced in function "int __cdecl invoke_main(void)" (?invoke_main##YAHXZ) dating c:\Users\Chris\documents\visual studio 2015\Projects\dating\MSVCRTD.lib(exe_winmain.obj) 1
Error LNK1120 1 unresolved externals dating c:\users\chris\documents\visual
studio 2015\Projects\dating\Debug\dating.exe 1
Code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
//Declares function
void getInput(char *userInput1, char *userInput2, char *userInput3);
//Declares variables.
int main(void) {
char userInput[100];
printf("Enter a date in this format : MM/DD/YY:");
//Captures users input
scanf("%s", &userInput);
//Divides the 3 dates entered into 3 variables.
char *userInput1 = strtok(userInput, "/");
char *userInput2 = strtok(NULL, "/");
//Used X to capture the last end of integers entered.
char *userInput3 = strtok(NULL, "X");
//Called function.
getInput(*userInput1, *userInput2, *userInput3);
system("pause");
return 0;
}
void getInput(char *userInput1, char *userInput2, char *userInput3)
{
// If user inputs a valid date this will run.
if (0 > *userInput1<12, 0>*userInput2<31, 0>*userInput3 < 99) {
// If user month input is this...
switch (*userInput1) {
//if User month input is 02 this will run
case 02:
//If user year is a leap year this will run
if (*userInput3 % 4 == 0) {
//If user day is inbetween 0-29 it will say the date is valid.
if (0 > *userInput2 > 29) {
printf("You entered a valid date, %s/%s/%s", *userInput1, *userInput2, *userInput3);
}
// If the day of the February isn't 0-29 it will print it is invalid.
else
printf("Invalid date.");
}
case 04:
//Their are only 30 days in April, if user Inputs 31 it is invalid.
if (*userInput2 == 31) {
printf("Invalid date.");
}
//Every other date should be valid because the main if else statement filters it all out.
else {
("You entered a valid date, %s/%s/%s", *userInput1, *userInput2, *userInput3);
}
case 06:
if (*userInput2 == 31) {
printf("Invalid date.");
}
//Every other date should be valid because the main if else statement filters it all out.
else {
("You entered a valid date, %s/%s/%s", *userInput1, *userInput2, *userInput3);
}
case 11:
if (*userInput2 == 31) {
printf("Invalid date.");
}
//Every other date should be valid because the main if else statement filters it all out.
else {
("You entered a valid date, %s/%s/%s", *userInput1, *userInput2, *userInput3);
}
break;
}
}
//If the user enters a date that isn't valid , Invalid date prints.
else {
printf("Invalid date.");
}
return 0;
}

Answer 1

You pass characters instead of pointers to getinput():
getInput(*userInput1, *userInput2, *userInput3);
Try this instead:
getInput(userInput1, userInput2, userInput3);
The warning you get from the compiler regarding scanf() are indications of potential problems:
scanf is unsafe: indeed you do not limit the number of characters to store into the userInput array, and you should not pass the address of the array, but the address of its first entry, and you should check the return value:
if (scanf("%99s", userInput) != 1) {
/* handle input failure */
}
strtok is unsafe to use in nested contexts. You do not do this in the above code, but it is difficult for the compiler to verify and it would be safer to use strtok_s or strtok_r instead.
You have further problems in function getInput():
You should check if any of the arguments are NULL.
if (0 > *userInput1<12, 0>*userInput2<31, 0>*userInput3 < 99) { is a valid C expression, but not what you intend to test. Write this instead:
if (*userInput1 > 0 && *userInput1 < 12
&& *userInput2 > 0 && *userInput2 < 31
&& *userInput3 > 0 && *userInput3 < 99) {
...
}
But note however that you are testing characters, not the decimal value encoded into these characters. You should first convert these strings into numbers with atoi() or strtol(), or use a different scanf() conversion.
Note that leap years are not strictly multiples of 4, you might need to use the Gregorian rule if you want to handle years outside the 1901..2099 range. I assume YY implies 20YY, but this would be incorrect if you ask for birthdays.
You missed that September also has 30 days.
Here is a corrected and simplified version:
#include <stdio.h>
#include <string.h>
int check_date(int month, int day, int year);
int main(void) {
char userInput[100];
int day, month, year;
printf("Enter a date in this format : MM/DD/YY:");
//Captures users input
if (scanf("%d/%d/%d", &month, &day, &year) == 3) {
check_date(day, month, year);
} else {
printf("incorrect input\n");
}
system("pause");
return 0;
}
int check_date(int month, int day, int year) {
int valid = 1;
// If user inputs a valid date this will run.
if (month <= 0 || month > 12 || day <= 0 || day > 31 || year < 0 || year > 99) {
valid = 0;
} else {
switch (month) {
//if User month input is 02 this will run
case 02:
//If user year is a leap year this will run
if (year % 4 == 0) {
if (day > 29)
valid = 0;
} else {
if (day <= 28)
valid = 0;
}
break;
case 4:
case 6:
case 9:
case 11:
if (month > 30)
valid = 0;
break;
}
}
if (valid) {
printf("You entered a valid date, %d/%d/%d\n", month, day, year);
return 1;
} else {
printf("Invalid date\n");
return 0;
}
}