GDB 调试遇到??的问题
今天总算解决了一个大的bug,爽！
我的程序crash,有了coredump文件，在Linux PC上用arm-linux-gdb debug it. The result is:
#0 0x4022b178 in ?? ()
(gdb) bt
#0 0x4022b178 in ?? ()
#1 0x4022b134 in ?? ()
#2 0x4022b134 in ?? ()
Backtrace stopped: previous frame identical to this frame (corrupt stack?)
(gdb)
why? I can‘t locate the correct location, find the really reason.
看看加载的内容
GNU gdb 6.6
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This GDB was configured as "--host=i686-pc-linux-gnu --target=arm-linux"...
warning: core file may not match specified executable file.
warning: .dynamic section for "/lib/libdl.so.2" is not at the expected address (wrong library or version mismatch?)
warning: .dynamic section for "/lib/libpthread.so.0" is not at the expected address (wrong library or version mismatch?)
Error while mapping shared library sections:
/lib/libstdc++.so.6: No such file or directory.
warning: .dynamic section for "/lib/libm.so.6" is not at the expected address (wrong library or version mismatch?)
warning: .dynamic section for "/lib/libgcc_s.so.1" is not at the expected address (wrong library or version mismatch?)
warning: .dynamic section for "/lib/libc.so.6" is not at the expected address (wrong library or version mismatch?)
warning: .dynamic section for "/lib/ld-linux.so.2" is not at the expected address (wrong library or version mismatch?)
warning: .dynamic section for "/lib/libnss_files.so.2" is not at the expected address (wrong library or version mismatch?)
Reading symbols from /lib/libdl.so.2...done.
Loaded symbols for /lib/libdl.so.2
Reading symbols from /lib/libpthread.so.0...done.
Loaded symbols for /lib/libpthread.so.0
Symbol file not found for /lib/libstdc++.so.6
Reading symbols from /lib/libm.so.6...done.
Loaded symbols for /lib/libm.so.6
Reading symbols from /lib/libgcc_s.so.1...done.
Loaded symbols for /lib/libgcc_s.so.1
Reading symbols from /lib/libc.so.6...done.
Loaded symbols for /lib/libc.so.6
Reading symbols from /lib/ld-linux.so.2...done.
Loaded symbols for /lib/ld-linux.so.2
Reading symbols from /lib/libnss_files.so.2...done.
Loaded symbols for /lib/libnss_files.so.2
Core was generated by `./6800plusEth.bin‘.
Program terminated with signal 11, Segmentation fault.
一些库找不到(/lib/libstdc++.so.6)，或者版本不匹配。我不应该加载/lib/libdl..so.... 这些文件，这是针对X86的。
所以两个命令至关重要:
set solib-absolute-prefix -- Set prefix for loading absolute shared library symbol files
set solib-search-path -- Set the search path for loading non-absolute shared library symbol files
比如：set solib-... /usr/local/arm-linux/arm-linux/lib/, 两个参数的值一样就可以了。
先启动arm-linux-gdb,设置变量以后，via core-file load core dump file to analyze it.
#gdb
#set solib-absolute-prefix "library path"
#set solib-search-path "library path"
#file file.debug
#core-file core.1234
但是还是不能准确定位，查询embedded linux版本：
uname -a
ls -l /usr/arm-linux/gcc-3.4.1-glibc-2.3.3/arm-linux/lib/libc-2.3.3.so
Linux PC上的呢：
ll /usr/local/arm/3.4.1/arm-linux/lib/libc-2.3.2.so
原来库文件不对，一个是2.3.3，另一个是2.3.2，此时发现版本匹配是至关的重要啊！！
换了一个Linux PC，它的交叉编译环境是2.3.3
哈哈！立即定位到了错误的原因！！
///
一.关于gdb调试core文件总是一堆问号的问题
问题描述：已经在编译选项中加入了-g，但是查看core文件时，还是一堆问号，使用的命令为:gdb -c core
解决方案：由于gdb -c core这样的使用在有些系统下支持不是很好，所以推荐用如下两种方法：
1）gdb exe
(gdb) core-file core
2）gdb -c core
(gdb) file exe
而其中第二种方法在某些系统上也是不好用的，所以就用第一种即可。