A example of a nop pad which confuses gdb's function boundary testing..

Anti-debugger nullpad

#define NPAD_START asm volatile ( \
    "pushl %eax      \n"
    "movl  %esp, %eax\n")
#define NPAD asm volatile ("addb %al, (%eax)\n")
#define NPAD_END asm volatile ("popl %eax\n")
#define NPAD_40 NPAD_START; \
    NPAD; NPAD; NPAD; NPAD; \
    NPAD; NPAD; NPAD; NPAD; \
    NPAD; NPAD; NPAD; NPAD; \
    NPAD; NPAD; NPAD; NPAD; \
    NPAD; NPAD; NPAD; NPAD; \
    NPAD_END;