valgrind基礎

valgrind

官網

原理

官網解釋
Your program is then run on a synthetic CPU provided by the Valgrind core. As new code is executed for the first time, the core hands the code to the selected tool. The tool adds its own instrumentation code to this and hands the result back to the core, which coordinates the continued execution of this instrumented code.

stackoverflow解釋
valgrind provides a virtual processor that executes your application. However, before your application instructions are processed, they are passed to tools (such as memcheck). These tools are kind of like plugins, and they are able to modify your application before it is run on the processor.
The great thing about this approach is that you don't have to modify or relink your program at all to run it in valgrind. It does cause your program to run slower, however valgrind isn't meant to measure performance or run during normal execution of your application, so this isn't really an issue.

安裝

源碼地址

使用以下命令更簡單些

yum install valgrind

參數

# When enabled, Valgrind will trace into sub-processes initiated via the exec system call.
# This is necessary for multi-process programs.
# Note that Valgrind does trace into the child of a fork (it would be difficult not to, 
# since fork makes an identical copy of a process), so this option is arguably badly named.
# However, most children of fork calls immediately call exec anyway.

--trace-children=<yes|no> [default: no]

Memcheck

功能

1. Memory leaks.
2. Using undefined values, i.e. values that have not been initialised, or that have been derived from other undefined values.
3. Accessing memory you shouldn't, e.g. overrunning and underrunning heap blocks, overrunning the top of the stack, and accessing memory after it has been freed.
4. Incorrect freeing of heap memory, such as double-freeing heap blocks, or mismatched use of malloc/new/new[] versus free/delete/delete[]
5. Overlapping src and dst pointers in memcpy and related functions.
6. Passing a fishy (presumably negative) value to the size parameter of a memory allocation function.

使用

#編譯文件，加參數 -g
clang++ -g -Wall memcheck_test.cc -o memcheck_test

#--tool=memcheck 參數缺省
#--leak-check=full，內存泄的具體信息
#--log-file=log_file.txt，輸出信息重定向到文件中
valgrind --leak-check=full --log-file=log_file.txt memcheck_test

Helgrind

功能

1. Misuses of the POSIX pthreads API
2. Potential deadlocks arising from lock ordering problems
3. Data races -- accessing memory without adequate locking or synchronisation

使用

valgrind --tool=helgrind memcheck_test

如何高效實用Helgrind

連接

callgrind

功能

Callgrind is a profiling tool that records the call history among functions in a program's run as a call-graph.

使用

valgrind --tool=callgrind --separate-threads=yes ./callgrind_test
#函數調用狀況總覽
callgrind_annotate callgrind.out.<pid>

#結合源文件
#注意.cc文件目錄格式要和上面命令產生的路徑格式一致
callgrind_annotate callgrind.out.<pid> callgrind_test.cc

使用kcachegrind工具

yum install kcachegrind
yum install graphviz
kcachegrind callgrind.out.<pid>

QA

連接