I run `"crash_demo.run"` by `spawn-fcgi` . How to collect `core` file

1. Question

I run "crash_demo.run" by spawn-fcgi . How to collect core file .

2. Background & Environment

I'm exolore C++ Web Programming .

1. web-server : nginx
2. CGI(FastCGI) : fastcgipp 3.0
3. CGI Wrapper : spawn-fcgi
   • I didn't use FCGI Wrap which ngifix supplied .
   • I understand FCGI Wrap be drive by spawn-fcgi , Of course this is off topic .
4. My c++ application . (be called crash_demo) .

3. Step to reproduce exception

1. crash_demo insert code throw "test exception str, check _core_ file" , build got crash_demo.run
2. run nginx : sudo nginx -c my_nginx_custom.config
3. ulimit -c unlimited
4. run crash_demo.run by spawn-fcgi : spawn-fcgi -a 127.0.0.1 -p 9000 -f /path/crash_demo.run
5. test the normal http request , and http request can be completed normally .
6. test the crash_demo http request , got 5xx response .
   • The directory where crash_demo.run is located does not see the core file

My guess

1. core file not generate .
2. core file is generated , but i don't the file path .

Does anyone know what happened?

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Solution update

My question is flawed .

Thanks @sehe , my step :

1. I read two webpage
   1. https://man7.org/linux/man-pages/man5/core.5.html
   2. https://zhuanlan.zhihu.com/p/240633280
2. update my /proc/sys/kernel/core_pattern
   • core -> core_%e_%p_%t
3. ulimit -c unlimited
4. spawn-fcgi -a 127.0.0.1 -p 9000 -f /path/crash_demo.run
5. sudo find / core_ | grep core_crash_demo
   • result /path/core_crash_demo._5080_1652169152

So , my guess on my question is failed .

The fact is , I don't generate core file , when my question.

When my generated core file successed , the core file path is crash_demo.run parent directory .

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Solution update 2

we whant to know two point :

1. how generate core dump file
2. how to fine exception code by core dump file

how generate core dump file？

Reference the file : core manual

core manual write many point , I just list the point i care :

1. system limit core dump file size , we need unlimit it:

• ulimit -a check limit / ulimit -c unlimited cancel limit

2. fix /proc/sys/kernel/core_pattern

• default value is core
• fix it to -> core_%e_%p_%t mean core_your_execute_file_name_pid_timestemp
• fix cmd : sudo bash -c 'echo core_%e_%p_%t > /proc/sys/kernel/core_pattern'

now run your exception , you can got core file .

• maby you need search it : sudo find / core_ | grep core_

how to fine exception code by core dump file ？

• I use vscode , fix launch.json , add coreDumpPath , refrence : https://code.visualstudio.com/docs/cpp/cpp-debug#_memory-dump-debugging

This question is probably more for askubuntu.com or serverfault.stackexchange.com.

You likely need to configure core dump. Since we don't know the platform, I'm assuming likely a Linux. See e.g. core(5):

There are various circumstances in which a core dump file is not produced

In my experience what's required is setting a core pattern (/proc/sys/kernel/core_pattern)