Debugging with GDB requires some advance settings in Ubuntu system.
1. Install gdb
Some versions of the system may not be installed this tool, you need to install it yourself.
cv@cv:~# sudo apt install gdb
2. Set the ulimit parameters
ulimit is a built-in feature of the Linux system, set limits for the use by the Shell process and its children it generates resources.
ulimit -a displays all the current limit information.
cv@cv:~# ulimit -a core file size (blocks, -c) unlimited data seg size (kbytes, -d) unlimited scheduling priority (-e) 0 file size (blocks, -f) unlimited pending signals (-i) 515120 max locked memory (kbytes, -l) 64 max memory size (kbytes, -m) unlimited open files (-n) 1048576 pipe size (512 bytes, -p) 8 POSIX message queues (bytes, -q) 819200 real-time priority (-r) 0 stack size (kbytes, -s) 8192 cpu time (seconds, -t) unlimited max user processes (-u) unlimited virtual memory (kbytes, -v) unlimited file locks (-x) unlimitedIn the Ubuntu system, the default core file size is zero, I've already set up, shown as core file size (blocks, -c) unlimited
If the display is 0, that does not produce core files in the event Segmentation Fault (core dump), not by the GDB debugger. -C set by parameters. After setting can re-use the above parameters -a view the results.
cv@cv:~# ulimit -c unlimited
3. Set core_pattern
After sending the changed parameter represents the core dump, what to do with the core file.
cv@cv:~# cat /proc/sys/kernel/core_pattern coreIf the display is related parameters apport, expressed in the Ubuntu system, handling mechanism for the core dump it as a bug is a bug check if the bug is reported on, in which case we can not use our program error debugger GDB .
|/usr/share/apport/apport %p %s %c %PCan be modified to core. It can be achieved by the following operation.
cv@cv: ~# sudo service apport stop
4. Set the translation parameters CMAKE_BUILD_TYPE
If set to RELEASE mode, the core file GDB displays core dump is generated when an error occurs, you can find little information, only the function name problems arise, of course, generally can easily navigate to the error location.
cv@cv: ~# gdb main core.31126 GNU gdb (Ubuntu 7.11.1-0ubuntu1~16.5) 7.11.1 Copyright (C) 2016 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html> This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. Type "show copying" and "show warranty" for details. This GDB was configured as "x86_64-linux-gnu". Type "show configuration" for configuration details. For bug reporting instructions, please see: <http://www.gnu.org/software/gdb/bugs/>. Find the GDB manual and other documentation resources online at: <http://www.gnu.org/software/gdb/documentation/>. For help, type "help". Type "apropos word" to search for commands related to "word"... Reading symbols from main...(no debugging symbols found)...done. [New LWP 31126] Core was generated by `./main'. Program terminated with signal SIGSEGV, Segmentation fault. #0 0x0000000000401761 in github::Option::Run() () (gdb) bt #0 0x0000000000401761 in github::Option::Run() () #1 0x0000000000400ff0 in main () (gdb) qIn contrast, if set to DEBUG mode, the information obtained even richer.
cv@cv: ~# gdb main core.30926 GNU gdb (Ubuntu 7.11.1-0ubuntu1~16.5) 7.11.1 Copyright (C) 2016 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html> This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. Type "show copying" and "show warranty" for details. This GDB was configured as "x86_64-linux-gnu". Type "show configuration" for configuration details. For bug reporting instructions, please see: <http://www.gnu.org/software/gdb/bugs/>. Find the GDB manual and other documentation resources online at: <http://www.gnu.org/software/gdb/documentation/>. For help, type "help". Type "apropos word" to search for commands related to "word"... Reading symbols from main...done. [New LWP 30926] Core was generated by `./main'. Program terminated with signal SIGSEGV, Segmentation fault. #0 0x00000000004021c5 in github::Option::Run (this=0x7fff6ea3f6b0) at /root/mvs_project/git_repo_for_trail/src/CacheFunction.cc:42 42 std::cout << root->next->val << std::endl; (gdb) bt #0 0x00000000004021c5 in github::Option::Run (this=0x7fff6ea3f6b0) at /root/mvs_project/git_repo_for_trail/src/CacheFunction.cc:42 #1 0x0000000000401333 in main (argc=1, argv=0x7fff6ea3f7f8) at /root/mvs_project/git_repo_for_trail/main.cc:11 (gdb) qNote that explicit information on both the results into the red section. Here I explicitly Ubuntu 16.04 system as an example.
5. Start Debugging
For example, I now file structure as follows
cv@cv: ~/mvs_project/git_repo_for_trail/build# tree -L 2 .. .. |-- CMakeLists.txt |-- README |-- build |-- main.cc `-- src |-- CMakeLists.txt |-- CacheFunction.cc `-- CacheFunction.hWhich CMakeLists.txt document reads as follows
#=============================================================================== # CMAKE VERSION #=============================================================================== cmake_minimum_required(VERSION 3.5) #=============================================================================== # PROJECT CONFIG #=============================================================================== project(GIT_REPO) #=============================================================================== # CMAKE CXX_STANDARD SET, CMAKE FLAGS AND CUDA SET #=============================================================================== # when version of cmake is higher than 3.1 CMAKE_CXX_STANDARD is valid # otherwise we can just use set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11") set(CMAKE_CXX_STANDARD 11) set(CMAKE_BUILD_TYPE DEBUG) #=============================================================================== # INCLUDE DIRECTORIES CONFIGURATION #=============================================================================== include_directories( src ) #=============================================================================== # SUB-DIRECTORY SET #=============================================================================== add_subdirectory(src) include_directories("src") #=============================================================================== # SOURCE FILES IN THE UPPEST FOLDER (such as main.cc CacheFunction.h # CacheFunction.cc) #=============================================================================== aux_source_directory(./src/ DIR_SRC) #=============================================================================== # EXECUTABLE PROGRAM SETTING #=============================================================================== add_executable(main main.cc ${DIR_SRC}) #=============================================================================== # TARGET LINK LIBRARIES NEEDED #=============================================================================== target_link_libraries(main src)Error occurs when running compiled by
cv@cv: ~/mvs_project/git_repo_for_trail/build# ./main The string elements are: h e l l o w o r l d ! 5 Segmentation fault (core dumped)If, after this time provided the steps above, in the build folder will produce the corresponding core document
cv@cv: ~/mvs_project/git_repo_for_trail/build# ll total 284 drwxr-xr-x 4 root root 4096 Jan 4 05:31 ./ drwxr-xr-x 5 root root 4096 Jan 4 05:31 ../ -rw-r--r-- 1 root root 11638 Jan 4 05:31 CMakeCache.txt drwxr-xr-x 5 root root 4096 Jan 4 05:31 CMakeFiles/ -rw-r--r-- 1 root root 5987 Jan 4 05:31 Makefile -rw-r--r-- 1 root root 1573 Jan 4 05:31 cmake_install.cmake -rw------- 1 root root 561152 Jan 4 05:31 core.31126 -rwxr-xr-x 1 root root 19136 Jan 4 05:31 main* drwxr-xr-x 3 root root 4096 Jan 4 05:31 src/Thus, we can enter the GDB debugger
cv@cv: ~/mvs_project/git_repo_for_trail/build# gdb main core.31126
In GDB environment, use the above instructions and their meaning.
backtrace (or bt) view all levels of function calls and parameters
list (or l) lists the source code, then the last position to the following, each row 10 column
quit (or q) quit gdb debugging environment
start running, the stop in front of the main function of the first command-line statement to wait
More commands and follow-up skills to be supplemented.
reference
[1] to improve the system performance by ulimit
[2] for the core dump debug ubuntu
[3] Debugging a segmentation fault using gdb
[4] use and gdb debugger command summary
[5] gdb Debugging Full Example (Tutorial): ncurses
[6] CppCon 2015: Greg Law 'Give me 15 minutes & I'll change your view of GDB'