👀 Views: 60 💬 Answers: 1 📅 Created: 2025-06-11

c sprintf buffer-overflow memory-management C

I'm working with unexpected behavior when using `sprintf` for formatting strings in C. I have a function where I'm trying to construct a formatted string with integer values but the output is not what I expect, and it sometimes leads to a buffer overrun. Here's the relevant portion of my code: ```c #include <stdio.h> #include <string.h> void format_string(char *buffer, int a, int b) { sprintf(buffer, "Values: %d %d", a, b); } int main() { char buf[20]; // Small buffer int x = 12345, y = 67890; // Values to format format_string(buf, x, y); printf("%s\n", buf); return 0; } ``` When I run this code, I expect to see `Values: 12345 67890`, but instead I'm getting garbage values or sometimes a segmentation fault due to buffer overflow. I checked that the buffer size is sufficient for smaller numbers, but it seems like the format string is exceeding the allocated space when the integer values are larger. I've tried increasing the size of `buf` to 50 characters, which seems to work for most cases, but I don't want to rely on arbitrary buffer sizes since it's not a scalable solution. I also considered using `snprintf`, but I'm unsure how to correctly implement that without running into similar issues. Any advice on how to safely handle formatted strings without risking buffer overruns would be greatly appreciated!