Assertion timeptr != nullptr

Question

I am working on logging in a DLL but getting the date and time causes an assertion.

The function is supposed to return a time like 3/3/2022 8:00:00.

But it causes an assertion, and a warning "'tm_v' could be '0'".

Code:

char* date_and_time()
{
    time_t timer = time(NULL);
    char buffer[26];
    struct tm* tm_v = malloc(sizeof(struct tm));
    tm_v = localtime_s(tm_v, &timer);
    strftime(buffer, 26, "%m/%d/%Y %H:%M:%S", tm_v);

    return buffer;
}

Assertion Message:
File: minkernel\crts\ucrt\src\appcrt\time\strftime.cpp
Line: 135
Expression: timeptr != nullptr

Answer 1

I fixed it by changing
time_t timer = time(NULL); to time_t timer; and
struct tm* tm_v = malloc(sizeof(struct tm)); to struct tm tm_v;

This is the function now:

char* date_and_time()
{
    char buffer[26];
    time_t timer;
    struct tm tm_v;
    time(&timer);
    localtime_s(&tm_v, &timer);
    strftime(buffer, 26, "%m/%d/%Y %I:%M:%S %p ", &tm_v);

    return buffer;
}