我对php-cgi有问题，因为它经常出错。父php-cgi派生了210个其他子项，而它就是其中一个失败的子项。
我已经构建了它的调试副本（-g-O0），并为glibc等加载了调试符号。当我查看核心转储时，我得到了以下内容：
delivery101:/cored# gdb /usr/bin/php-cgi 28133_1446799964.core
GNU gdb (GDB) CentOS (7.0.1-45.el5.centos)
Copyright (C) 2009 Free Software Foundation, Inc.
This GDB was configured as "x86_64-redhat-linux-gnu".
Reading symbols from /usr/bin/php-cgi...done.
Attaching to program: /usr/bin/php-cgi, process 28133
ptrace: No such process.
[New Thread 28195]
[New Thread 28133]
Reading symbols from /lib64/libcrypt.so.1...Reading symbols from /usr/lib/debug/lib64/libcrypt-2.5.so.debug...done
Loaded symbols for /lib64/libcrypt.so.1
Reading symbols from /usr/lib64/libedit.so.0...(no debugging symbols found)...done.
Loaded symbols for /usr/lib64/libedit.so.0
Reading symbols from /usr/lib64/libncurses.so.5...(no debugging symbols found)...done.
Loaded symbols for /usr/lib64/libncurses.so.5
Reading symbols from /usr/lib64/libgmp.so.3...(no debugging symbols found)...done.
Loaded symbols for /usr/lib64/libgmp.so.3
Reading symbols from /usr/lib64/libbz2.so.1...(no debugging symbols found)...done.
Loaded symbols for /usr/lib64/libbz2.so.1
Reading symbols from /usr/lib64/libz.so.1...(no debugging symbols found)...done.
Loaded symbols for /usr/lib64/libz.so.1
Reading symbols from /lib64/librt.so.1...Reading symbols from /usr/lib/debug/lib64/librt-2.5.so.debug...done.
Loaded symbols for /lib64/librt.so.1
Reading symbols from /lib64/libm.so.6...Reading symbols from /usr/lib/debug/lib64/libm-2.5.so.debug...done.
Loaded symbols for /lib64/libm.so.6
Reading symbols from /lib64/libdl.so.2...Reading symbols from /usr/lib/debug/lib64/libdl-2.5.so.debug...done.
Loaded symbols for /lib64/libdl.so.2
Reading symbols from /lib64/libnsl.so.1...Reading symbols from /usr/lib/debug/lib64/libnsl-2.5.so.debug...done.
Loaded symbols for /lib64/libnsl.so.1
Reading symbols from /usr/lib64/libxml2.so.2...(no debugging symbols found)...done.
Loaded symbols for /usr/lib64/libxml2.so.2
Reading symbols from /usr/lib64/libgssapi_krb5.so.2...(no debugging symbols found)...done.
Loaded symbols for /usr/lib64/libgssapi_krb5.so.2
Reading symbols from /usr/lib64/libkrb5.so.3...(no debugging symbols found)...done.
Loaded symbols for /usr/lib64/libkrb5.so.3
Reading symbols from /usr/lib64/libk5crypto.so.3...(no debugging symbols found)...done.
Loaded symbols for /usr/lib64/libk5crypto.so.3
Reading symbols from /lib64/libcom_err.so.2...(no debugging symbols found)...done.
Loaded symbols for /lib64/libcom_err.so.2
Reading symbols from /lib64/libssl.so.6...(no debugging symbols found)...done.
Loaded symbols for /lib64/libssl.so.6
Reading symbols from /lib64/libcrypto.so.6...(no debugging symbols found)...done.
Loaded symbols for /lib64/libcrypto.so.6
Reading symbols from /lib64/libc.so.6...Reading symbols from /usr/lib/debug/lib64/libc-2.5.so.debug...(no debugging symbols found)...done.
Loaded symbols for /lib64/libc.so.6
Reading symbols from /lib64/libresolv.so.2...Reading symbols from /usr/lib/debug/lib64/libresolv-2.5.so.debug...done.
Loaded symbols for /lib64/libresolv.so.2
Reading symbols from /lib64/libpthread.so.0...Reading symbols from /usr/lib/debug/lib64/libpthread-2.5.so.debug...done.
[Thread debugging using libthread_db enabled]
Loaded symbols for /lib64/libpthread.so.0
Reading symbols from /lib64/ld-linux-x86-64.so.2...Reading symbols from /usr/lib/debug/lib64/ld-2.5.so.debug...done.
Loaded symbols for /lib64/ld-linux-x86-64.so.2
Reading symbols from /usr/lib64/libkrb5support.so.0...(no debugging symbols found)...done.
Loaded symbols for /usr/lib64/libkrb5support.so.0
Reading symbols from /lib64/libkeyutils.so.1...(no debugging symbols found)...done.
Loaded symbols for /lib64/libkeyutils.so.1
Reading symbols from /lib64/libselinux.so.1...(no debugging symbols found)...done.
Loaded symbols for /lib64/libselinux.so.1
Reading symbols from /lib64/libsepol.so.1...(no debugging symbols found)...done.
Loaded symbols for /lib64/libsepol.so.1
Reading symbols from /lib64/libgcc_s.so.1...(no debugging symbols found)...done.
Loaded symbols for /lib64/libgcc_s.so.1
Reading symbols from /lib64/libnss_files.so.2...Reading symbols from /usr/lib/debug/lib64/libnss_files-2.5.so.debug...done.
Loaded symbols for /lib64/libnss_files.so.2
warning: no loadable sections found in added symbol-file system-supplied DSO at 0x7fff6956d000
Core was generated by `/usr/bin/php-cgi'.
Program terminated with signal 11, Segmentation fault.
#0 0x00002af461e02678 in ?? ()
所以我看看有哪些线程：
(gdb) info threads
2 Thread 0x2af45de68af0 (LWP 28133) 0x000000315da48370 in krb5int_kt_finalize () from /usr/lib64/libkrb5.so.3
* 1 Thread 0x2af487823940 (LWP 28195) 0x00002af461e02678 in ?? ()
据我所知，线程1旁边的*表示这是导致segfault的线程。所以我仔细看了一下：
(gdb) bt full
#0 0x00002af461e02678 in ?? ()
No symbol table info available.
#1 0x0000000018733e78 in ?? ()
No symbol table info available.
#2 0x00002af4878230c0 in ?? ()
No symbol table info available.
#3 0x00002af487823100 in ?? ()
No symbol table info available.
#4 0x00002af461dfed8d in ?? ()
No symbol table info available.
#5 0x0000000000000000 in ?? ()
No symbol table info available.
我不知道线程从哪里来（或者如何找到），也不知道回溯有什么用处；缺少符号只是因为我没有为所有东西加载符号吗？或者这可能表明问题本身（缓冲区溢出？）
我的问题是：我如何才能找到这个线程的来源和它是什么？
如果你需要更多的细节，请告诉我。
我怎样才能找到这个线程的来源和它是什么？
你得到的无用堆栈跟踪有几种可能：
- 您正在分析由优化的php-cgi生成的核心，但向GDB提供php-cgi的调试版本。这根本不起作用：你需要使用产生核心的二进制文件来分析核心
- 您可能正在分析机器上的堆芯转储（例如开发），该机器与生产堆芯的机器（例如生产）不同。这样做是可能的，但必须小心让GDB使用核心转储时使用的共享库的精确版本
- 在为glibc等安装调试符号时，您可能还更新了一些库，导致在核心转储时使用的符号和在分析时使用的不匹配
- php-cgi可能使用了某种
JIT编译，而崩溃发生在JIT-ted代码中 - 程序可能只是简单地跳转到了与任何函数都不对应的随机地址