GDB总结

1，调试其他机器上生成的core dump 文件，遇到无法解析的符号怎么办？

典型的是，bt查看函数调用帧栈时，显示出“??”。

(gdb) bt
#0  0x00007f4187251925 in raise () from /lib64/libc.so.6
#1  0x00007f4187253105 in abort () from /lib64/libc.so.6
#2  0x00007f4188b184b9 in ?? ()
#3  0x0000000000000000 in ?? ()

这种情况一般是由于找不到所需的.so动态库导致的，可通过info share命令查看加载的动态库信息。

(gdb) info share
From                     To                                Syms Read   Shared Object Library
                                                                        No                 /lib64/libglog.so.0
0x00007f41884085a0  0x00007f4188409cc8  Yes (*)          /lib64/libuuid.so.1
0x00007f41881ef760  0x00007f41881fb0c8   Yes (*)           /lib64/libpthread.so.0
0x00007f4186e05de0  0x00007f4186e06998  Yes (*)         /lib64/libdl.so.2
(*): Shared library is missing debugging information.

Syms标记为No就表示没有在相应目录中找到所需的动态库，此时可通过set solib-search-path设置动态库的搜索路径（支持设置多个搜索路径，路径之间使用“:”隔开）；也可通过set solib-absolute-prefix （别名 set sysroot）指定搜索前缀。具体解释如下：

set solib-absolute-prefix path
If this variable is set, path will be used as a prefix for any absolute shared library paths; many runtime loaders store the absolute paths to the shared library in the target program's memory. If you use solib-absolute-prefix to find shared libraries, they need to be laid out in the same way that they are on the target, with e.g. a /usr/lib hierarchy under path.
You can set the default value of solib-absolute-prefix by using the configure-time -with-sysroot option.
show solib-absolute-prefix
Display the current shared library prefix.
set solib-search-path path
If this variable is set, path is a colon-separated list of directories to search for shared libraries. solib-search-path is used after solib-absolute-prefix fails to locate the library, or if the path to the library is relative instead of absolute. If you want to use solib-search-path instead of solib-absolute-prefix, be sure to set solib-absolute-prefix to a nonexistant directory to prevent gdb from finding your host's libraries.
show solib-search-path
Display the current shared library search path.

2，如何让gdb启动后自动执行某些命令
比如我们用GDB调试时想忽略某个信号，为避免每次调试时都手动输入命令，可以将命令写入用户主目录的.gdbinit文件。如， echo "handle SIGPIPE nostop noprint nopass" > ~/.gdbinit