You have learned about the importance of **null-termination**, **buffer sizes**, and the risks of **buffer overflow** when working with strings in C. Now, you will put these concepts into practice by implementing a function to copy one string into another, ensuring that you do not write past the end of the destination buffer and that the copied string is always properly **null-terminated**. This challenge will help solidify your understanding of safe string copying techniques.


#define CATCH_CONFIG_MAIN
#include <catch2/catch.hpp>

int _testmain();


void safe_string_copy(char *dest, const char *src, int dest_size);

TEST_CASE("Copies up to dest_size - 1 characters and null-terminates", "[safe_string_copy]") {
    char dest[6];
    const char *src = "HelloWorld";
    safe_string_copy(dest, src, sizeof(dest));
    REQUIRE(dest[5] == '\\0'); // Always null-terminated
    REQUIRE(dest[0] == 'H');
    REQUIRE(dest[1] == 'e');
    REQUIRE(dest[2] == 'l');
    REQUIRE(dest[3] == 'l');
    REQUIRE(dest[4] == 'o');
}

TEST_CASE("Null-terminator is present even if source is longer than buffer", "[safe_string_copy]") {
    char dest[4];
    const char *src = "ABCDEFG";
    safe_string_copy(dest, src, sizeof(dest));
    REQUIRE(dest[3] == '\\0');
    REQUIRE(dest[0] == 'A');
    REQUIRE(dest[1] == 'B');
    REQUIRE(dest[2] == 'C');
}

TEST_CASE("Copies entire source if it fits in buffer", "[safe_string_copy]") {
    char dest[10];
    const char *src = "Hi";
    safe_string_copy(dest, src, sizeof(dest));
    REQUIRE(dest[0] == 'H');
    REQUIRE(dest[1] == 'i');
    REQUIRE(dest[2] == '\\0');
}

TEST_CASE("Does not write past destination buffer bounds", "[safe_string_copy]") {
    char dest[3] = {'x', 'y', 'z'};
    const char *src = "12345";
    safe_string_copy(dest, src, sizeof(dest));
    REQUIRE(dest[0] == '1');
    REQUIRE(dest[1] == '2');
    REQUIRE(dest[2] == '\\0');
}

test.cpp

Learn how strings are represented and manipulated in the C programming language. Understand the unique characteristics of C strings, including memory management, null-termination, and common string operations.

Explore how strings are represented as arrays of characters in C, the role of null-termination, and the implications for memory management.

Learn how to initialize strings, read input from the user, and output strings in C.

Explore the most frequently used string operations in C, including copying, comparison, concatenation, and length calculation.

Challenge: Copying Strings

Solution