strcat

Writing text without overflowing16

Objective

Implement a function that appends the src string onto the end of the dst string, then returns dst.

Steps

First walk dst to find its \0, that terminator marks where the existing string ends and where the new characters must start.
Copy every character of src to that position, advancing through both buffers.
Write a final \0 after the last copied character so the result is a valid, null-terminated string.
Return the original dst pointer. Assume dst is large enough to hold both strings.
Appending an empty src must leave dst unchanged.

examples

$ strcat("src/", "main.c")

src/main.c

$ strcat("rebase done", "")

rebase done

Constraints

Expected files

strcat.c

Allowed functions

None. Write every helper yourself.

libc

Standard C library

Implements the contract of a function from the standard C library.

Tests

Run the tests to grade your code

Build

01Append to an empty destination

02Append to a non-empty destination

03Build a branch name

04Append an empty source

05Both strings empty

06Build a file path

07Result stays NUL-terminated over dirty memory

strcat

Objective

Implement a function that appends the src string onto the end of the dst string, then returns dst.

Steps

First walk dst to find its \0, that terminator marks where the existing string ends and where the new characters must start.
Copy every character of src to that position, advancing through both buffers.
Write a final \0 after the last copied character so the result is a valid, null-terminated string.
Return the original dst pointer. Assume dst is large enough to hold both strings.
Appending an empty src must leave dst unchanged.

examples

$ strcat("src/", "main.c")

src/main.c

$ strcat("rebase done", "")

rebase done

Constraints

Expected files

strcat.c

Allowed functions

None. Write every helper yourself.

libc

Standard C library

Implements the contract of a function from the standard C library.

strcat

Writing text without overflowing16

Objective

Implement a function that appends the src string onto the end of the dst string, then returns dst.

Steps

First walk dst to find its \0, that terminator marks where the existing string ends and where the new characters must start.
Copy every character of src to that position, advancing through both buffers.
Write a final \0 after the last copied character so the result is a valid, null-terminated string.
Return the original dst pointer. Assume dst is large enough to hold both strings.
Appending an empty src must leave dst unchanged.

examples

$ strcat("src/", "main.c")

src/main.c

$ strcat("rebase done", "")

rebase done

Constraints

Expected files

strcat.c

Allowed functions

None. Write every helper yourself.

libc

Standard C library

Implements the contract of a function from the standard C library.

Tests

Run the tests to grade your code

Build

01Append to an empty destination

02Append to a non-empty destination

03Build a branch name

04Append an empty source

05Both strings empty

06Build a file path

07Result stays NUL-terminated over dirty memory