Linux SIGSEGV — Segmentation Fault Signal Handling & Debugging

Overview

Complete guide to Linux SIGSEGV (signal 11) segmentation fault: causes, debugging with GDB and core dumps, and common patterns in C/C++ programs.

Key Details

• SIGSEGV (signal 11) is sent when a process accesses memory outside its allowed address space
• The kernel's memory management unit (MMU) detects the invalid access and sends the signal
• Default action is to terminate the process and generate a core dump (if enabled)
• Common in C/C++ programs due to manual memory management
• Core dumps are stored according to /proc/sys/kernel/core_pattern

Common Causes

• Dereferencing NULL pointer (most common cause)
• Accessing array out of bounds (buffer overflow or underflow)
• Using memory after it has been freed (use-after-free)
• Stack overflow from infinite recursion
• Writing to read-only memory (e.g., string literal modification)

Steps

1. 1Enable core dumps: ulimit -c unlimited
2. 2Compile with debug symbols: gcc -g -O0 program.c -o program
3. 3Run under GDB: gdb ./program, then 'run', then 'bt' at crash for backtrace
4. 4Analyze core dump: gdb ./program core — then 'bt' for backtrace
5. 5Use Valgrind for memory error detection: valgrind --tool=memcheck ./program

Tags

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Frequently Asked Questions