C/C++: *** stack smashing detected ***: terminated — buffer overflow on the stack

Meaning

When a function returns, the guard value placed after its local arrays is checked. A write past the end of a char buf[16] (from strcpy, gets, scanf("%s"), sprintf or an off-by-one loop) changes it, producing this abort. The crash is reported at function exit, not at the faulty write.

Common causes

• strcpy, sprintf, gets or scanf("%s") into a fixed-size array
• Loop with <= instead of < writing one element past the end
• Wrong buffer length passed to read/memcpy
• Format specifier mismatch writing more bytes than expected

Detailed fix by platform

Code examples

#include <cstdio>
#include <cstring>

int main() {
    char name[8];
    const char* input = "Alexander";
    // std::strcpy(name, input);                 // 10 bytes into 8: stack smashing
    std::snprintf(name, sizeof name, "%s", input);   // truncates safely to "Alexand"
    std::puts(name);
}

How to diagnose

1. ASan — Which line does stack-buffer-overflow name?
2. Buffers — Fixed-size local arrays written to?
3. Loops — Any <= bound?

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