Gemini 3 Found a Stack Smash in a Hex Dump That I Missed

I spent the morning chasing a crash in our distributed engine. The stack trace pointed to a segfault deep inside folly::FiberManager.

gdb showed that a critical pointer was garbage: 0x676974736e6f5373.

Usually, I’d suspect a race condition or a use-after-free. I stared at the hex for a while, checking for alignment issues or bit-flips, but it just looked like random entropy.

Out of frustration, I pasted the info locals dump into Gemini 3. I didn't ask it to fix the code, I just asked: "What do you see?"

It didn't try to analyze the C++ logic. Instead, it treated the address as data. It pointed out that on an x86-64 (Little Endian) system, 0x676974736e6f5373 decodes perfectly to the ASCII string: "sSonstig".

It clicked immediately. "Sonstig" is German for "Miscellaneous".

It turns out a legacy localization function was writing the category name "Sonstiges" into a stack buffer that was too small. It overflowed and perfectly overwrote the FiberManager pointer with the bytes of the word.

I think we often focus too much on LLMs for "Code Generation" (writing boilerplate). For me, the real killer feature is Pattern Recognition in raw data. I would have stared at that hex for hours seeing only noise; the model recognized the semantic meaning in milliseconds.

Has anyone else found LLMs useful specifically for decoding raw dumps or logs like this?