kapstok / Post-mortem-debugging (public) (License: MIT) (since 2018-11-16) (hash sha1)
Simple sample on how post mortem debugging in C(++) works.
Clone URLs: https://rocketgit.com/user/kapstok/Post-mortem-debugging ssh://rocketgit@ssh.rocketgit.com/user/kapstok/Post-mortem-debugging git://git.rocketgit.com/user/kapstok/Post-mortem-debugging
master
List of commits:
Subject Hash Author Date (UTC)
Initial commit. 86c80da5a6a677f1686e50996b61fd51632259ba Jan Allersma 2018-05-18 13:12:38
Commit 86c80da5a6a677f1686e50996b61fd51632259ba - Initial commit.
Author: Jan Allersma
Author date (UTC): 2018-05-18 13:12
Committer name: Jan Allersma
Committer date (UTC): 2018-05-18 13:12
Parent(s):
Signing key:
Tree: 12bf7c01fc3b059faf7dca12f196f3ef2615e0b5
File Lines added Lines deleted
.gitignore 4 0
README.md 35 0
main.cpp 60 0
File .gitignore added (mode: 100644) (index 0000000..01db905)
1 *
2 !.gitignore
3 !main.cpp
4 !README.md
File README.md added (mode: 100644) (index 0000000..4945c5f)
1 # Fault handling
2
3 ## Compiling
4
5 > Commands executed from repository's root.
6
7 ```
8 g++ main.cpp -o exe
9 g++ main.cpp -g -o dbgexe
10 ```
11
12 ## Post mortem debugging
13
14 Running `./exe` results in this output:
15
16 ```
17 Fout 11 at 0:
18 Called from 4197438.
19 Aborted (geheugendump gemaakt)
20 ```
21
22 See what caused the error:
23
24 > Use the output from running ./exe ('Called from 4197438').
25
26 ```
27 gdb ./dbgexe
28 l *4197438
29 ```
30
31 As `gdb` states, the error was caused at line 57:
32
33 ```
34 0x400c3e is in main() (main.cpp:57).
35 ```
File main.cpp added (mode: 100644) (index 0000000..60d05db)
1 #include <list>
2 #include <iostream>
3
4 #include <unistd.h>
5 #include <signal.h>
6 #include <stdlib.h>
7 #include <sys/types.h>
8 #include <sys/wait.h>
9 #include <signal.h>
10
11 #include <sys/ucontext.h>
12 #include <ucontext.h>
13
14 void setHandler(void (*handler)(int,siginfo_t *,void *)) {
15 struct sigaction action;
16 action.sa_flags = SA_SIGINFO;
17 action.sa_sigaction = handler;
18
19 if (sigaction(SIGFPE, &action, NULL) == -1) {
20 std::cerr << "sigfpe: sigaction";
21 _exit(1);
22 }
23 if (sigaction(SIGSEGV, &action, NULL) == -1) {
24 std::cerr << "sigsegv: sigaction";
25 _exit(1);
26 }
27 if (sigaction(SIGILL, &action, NULL) == -1) {
28 std::cerr << "sigill: sigaction";
29 _exit(1);
30 }
31 if (sigaction(SIGBUS, &action, NULL) == -1) {
32 std::cerr << "sigbus: sigaction";
33 _exit(1);
34 }
35 }
36
37 void faultHandler(int signo, siginfo_t* info, void* extra) {
38 int i;
39
40 i = ((ucontext_t*)extra)->uc_mcontext.gregs[REG_RIP]; // x86_64
41 //i = ((ucontext_t*)extra)->uc_mcontext.arm_pc; // ARM
42
43 std::cout << "Fout " << (int)signo << " at ";
44 std::cout << (int&)info->si_addr << ": " << std::endl;
45 std::cout << "Called from " << (int)i << "." << std::endl;
46
47 abort();
48 }
49
50 int main() {
51 std::list<size_t*> subIterators;
52 size_t pubIterator = 0;
53 int* badptr = nullptr;
54
55 setHandler(faultHandler);
56
57 *badptr = 15;
58
59 return 0;
60 }
Hints:
Before first commit, do not forget to setup your git environment:
git config --global user.name "your_name_here"
git config --global user.email "your@email_here"

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