valgrind 检测内存泄漏，越界，未初始化

$ g++ -std=c++11 -g -o main_cpp main.cpp

$ valgrind --tool=memcheck --leak-check=full ./main_cpp

==31523== Memcheck, a memory error detector

==31523== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.

==31523== Using Valgrind-3.13.0 and LibVEX; rerun with -h for copyright info

==31523== Command: ./main_cpp

==31523==

==31523== Invalid read of size 4

==31523== at 0x400AD7: main (main.cpp:7)

==31523== Address 0x5ab5ca8 is 0 bytes after a block of size 40 alloc'd

==31523== at 0x4C2E216: operator new(unsigned long) (vg_replace_malloc.c:334)

==31523== by 0x4010D3: __gnu_cxx::new_allocator<int>::allocate(unsigned long, void const*) (new_allocator.h:104)

==31523== by 0x401040: std::allocator_traits<std::allocator<int> >::allocate(std::allocator<int>&, unsigned long) (alloc_traits.h:491)

==31523== by 0x400F91: std::_Vector_base<int, std::allocator<int> >::_M_allocate(unsigned long) (stl_vector.h:170)

==31523== by 0x400E7E: std::_Vector_base<int, std::allocator<int> >::_M_create_storage(unsigned long) (stl_vector.h:185)

==31523== by 0x400D1E: std::_Vector_base<int, std::allocator<int> >::_Vector_base(unsigned long, std::allocator<int> const&) (stl_vector.h:136)

==31523== by 0x400C11: std::vector<int, std::allocator<int> >::vector(unsigned long, int const&, std::allocator<int> const&) (stl_vector.h:291)

==31523== by 0x400AB9: main (main.cpp:6)

$ g++ -std=c++11 -g -o main_cpp main.cpp

$ valgrind --tool=memcheck --leak-check=full ./main_cpp

==31554== Memcheck, a memory error detector

==31554== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.

==31554== Using Valgrind-3.13.0 and LibVEX; rerun with -h for copyright info

==31554== Command: ./main_cpp

==31554==

==31554== Conditional jump or move depends on uninitialised value(s)

==31554== at 0x400852: main (main.cpp:6)