Memory checker - used to determine whether C program has memory errors

Memcheck

• Valgrind - popular Linux framework, comprises suite of tools that can be used to check for memory errors and profiling programs
• Valgrind can be run directly on existing executables - compile with -g argument for compiler to include debug info for Valgrind
• Good idea to turn off compiler optimizatilns with -o0 - slowdown give smore accurate Valgrind output
• Valgrind has additional built-in support to understand debug info by gcc compiler
• After preamble listening details of memcheck, Valgrind produces program output and summarizes heap usage - summary of errors detected
  • note all error by Valgrind is sent to the standard error stream

AddressSanitizer, asan

• Part of clang - fast memory checker
• Must create a custom executable with AddressSanitizer enabled
  • AddressSanitizer injects instrumentation at compile time
• Note that slowdown is minimal for AddressSanitizer
• enable at compile time with -fsanitize=address argument
• Recommended to use first level optimization, -O1, also use -fno-omit-frame-pointer to get “nicer stack traces”
• e.g. clang -O1 -fsanitize=address -fno-omit-frame-pointer -Wall -g test.c -o test
• Note that AddressSanitizer will only produce output if something went wrong during program execution, i.e. memory error is detected
• clang also has other sanitizers
• Most errors are fairly obvious

Uninitialized Memory

• If we forget to initialize a variable, we will get an error like “Conditional jump or move depends on uninitialized value(s)”