编译gdb注意事项:一定要用一个干净的build文件夹

上周收到gdb的通知邮件,说gdb 7.8已经release了。作为gdb的忠实用户,自然是体验一下了。我赶紧下了一个版本,然后build了一下,结果在最后link阶段,出了错误:

gcc: unrecognized option `-rdynamic’
ld: warning: file /usr/local/lib/libiconv.so: attempted multiple inclusion of file
Undefined                       first referenced
 symbol                             in file
observer_attach_exited              cli-interp.o
observer_notify_signal_exited       infrun.o
observer_attach_sync_execution_done cli-interp.o
observer_attach_command_error       cli-interp.o
observer_notify_signal_received     infrun.o
observer_attach_end_stepping_range  cli-interp.o
observer_attach_no_history          cli-interp.o
ptid_match                          remote.o
observer_notify_end_stepping_range  infrun.o
observer_notify_exited              infrun.o
observer_notify_no_history          infrun.o
observer_attach_signal_exited       cli-interp.o
observer_notify_command_error       event-loop.o
observer_notify_sync_execution_done infrun.o
observer_attach_signal_received     cli-interp.o
ld: fatal: symbol referencing errors. No output written to gdb
collect2: ld returned 1 exit status
Makefile:1334: recipe for target ‘gdb’ failed
make[2]: *** [gdb] Error 1
make[2]: Leaving directory ‘/export/home/nan/build_gdb/gdb’
Makefile:8667: recipe for target ‘all-gdb’ failed
make[1]: *** [all-gdb] Error 2
make[1]: Leaving directory ‘/export/home/nan/build_gdb’
Makefile:831: recipe for target ‘all’ failed
make: *** [all] Error 2

gdb的编译过程一向是最简单的,link错误我还是第一次碰到。我先是在gdb的IRC里讨论,接着又自己debug,检查代码文件和脚本,结果最后得到的结论是:因为我所用的build目录之前是编译7.7.1版本的,我因为偷懒,没有清空,导致现在编译7.8版本时会有问题,原因应该是link的还是7.7.1的目标文件。

最后得到的经验是:在编译gdb(或是其它软件)时,一定要准备一个干净的build文件夹,否则可能会有你意想不到的问题,像我碰到的在link阶段出问题还好办,如果在执行阶段出了问题,可就更难查了。

注:build文件夹是为了保持源码的干净,通常在源代码文件夹外,新建一个build文件夹,然后所有的configure,make操作等都在这个build文件夹下进行。例如:

mkdir build_gdb;
cd build_gdb;
../gdb-7.8/configure
make
make install

 

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