What to do if a segfault occurs in the php extension

The solution to a segmentation fault in PHP: first check "ulimit -a"; then set "ulimit -c unlimited" to not limit the size of the core file; then use gdb to run the program and the file recorded by the segmentation fault; finally specify The core file size is sufficient.

C programs under Linux often cause segment faults due to memory access errors and other reasons. At this time, if the system core dump function is turned on, then The memory image will be dumped to the hard disk. You can then use gdb to analyze the core file and restore the stack situation when the system segmentation fault occurred. This is very helpful for us to find program bugs.

Use ulimit -a to view the size limit of the system core file; use ulimit -c [kbytes] to set the size of the core file that the system allows to generate.

ulimit -c 0 does not generate core files

ulimit -c 100 sets the maximum core file to 100k

ulimit -c unlimited does not limit the core file size

Steps:

1. When a segmentation fault occurs, we check ulimit -a (core file size (blocks, -c) 0) and there is no file,

2. Setting: ulimit -c unlimited does not limit the core file size

3. Run the program, and when a segfault occurs, it will automatically be recorded in the core (php -f WorkWithArray.php)

4. ls -al core.* Under that file (-rw------- 1 leconte leconte 139264 01-06 22:3 1 core.2065)

5. Use gdb to run the program and segment fault Recorded files. (gdb ./test core.2065)

6. Will you mention which line is wrong?

The default core file size of many systems is 0. We can specify the core file size by adding the ulimit -c command to the shell startup script /etc/bashrc or ~/.bashrc to ensure The core file can be generated.

In addition, you can also set the file name template of the core file in /proc/sys/kernel/core_pattern. For details, please see the official man manual of core.

Related introduction:

The Linux ulimit command is used to control the resources of the shell program.

ulimit is a built-in command of the shell, which can be used to control the resources of the shell execution program.

Syntax

ulimit [-aHS][-c <core文件上限>][-d <数据节区大小>][-f <文件大小>][-m <内存大小>][-n <文件数目>][-p <缓冲区大小>][-s <堆叠大小>][-t <CPU时间>][-u <程序数目>][-v <虚拟内存大小>]

Parameters:

-a Displays the current resource limit settings.

-c b6b0704fb7b349af77ca9f3ad41a2c5e Set the maximum value of the core file in blocks.

-d 1519232b90db98d3e87306e448761991 The maximum value of the program data section, in KB.

-f ba5a6b460716877d3e6689c77a9de729 The largest file that the shell can create, in blocks.

-H Set the hard limit of resources, which is the limit set by the administrator.

-m 392406bbf8b37302fd1437cce5376c2a Specifies the upper limit of usable memory, in KB.

-n c62551de4c027ece3e59d90ee316c5ab Specifies the maximum number of files that can be opened at the same time.

-p 8edc7cfa23fd8b237e6a35701015e7cf Specifies the size of the pipe buffer in 512 bytes.

-s 1cd482feb27873c5277cd810401c8d35 Specifies the upper limit of the stack, in KB.

-S Set the flexible limit of resources.

-t fbfbe4e76445bd735c51a82e7a9fb6eb Specifies the upper limit of CPU usage time, in seconds.

-u 27825da1ff3a96f57d740c4576bb7fd7 The maximum number of programs that a user can open.

-v e8e960a91e8a47aae6c2ad3aee596076 Specifies the upper limit of virtual memory that can be used, in KB.

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