gdb：加载共享库的符号表 solib-search-path

原文地址::http://blog.chinaunix.net/uid-29065085-id-4703912.html

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1、set solib-search-path command----http://visualgdb.com/gdbreference/commands/set_solib-search-path

原文网址：http://visualgdb.com/gdbreference/commands/set_solib-search-path

set solib-search-path command

Specifies directories where GDB will search for shared libraries with symbols. This option is useful when debugging with gdbserver.

Syntax

set solib-search-path [Directories]
show solib-search-path

Parameters

Directories Specifies the list of directories separated by colon (:) on Linux or semicolon (;) on Windows where GDB will look for shared libraries when searching for symbols.

Typical use

This command is useful when debugging remote programs via gdbserver. If the shared library path on the remote computer and the GDB computer is different, GDB won't automatically find the local copy of the library and load its symbols unless the directory containing
it is specified in set solib-search-path.

E.g. if you have copied /home/testuser/libtest/libTest.so on the computer with GDB to /tmp/libTest.so on the computer with GDBServer, you will need to specify set solib-search-path /home/testuser/libtest in
order to get the symbols loaded.

Default value

The default value for the solib-search-path variable is "." that corresponds to the working directory of GDB (directory where GDB was launched unless changed using the cd command).

Examples

In this example we will debug a simple shared library with gdbserver:

#include 

int func()

{

    printf("In func()\n");

    return 0;

}

We will use a simple program to test our library:

#include 

int func();

int main()

{

    printf("In main()\n");

    func();

    return 0;

}

First, we build the application and the library and deploy it to another machine:

cd /home/testuser/libtest

g++ -ggdb -fPIC -shared lib.cpp -o libTest.so

g++ -ggdb main.cpp libTest.so -o testApp -Wl,--rpath='$ORIGIN'

scp testApp libTest.so deploy_machine:/tmp

Then we run gdbserver on the deploy_machine machine:

cd /tmp

gdbserver :2000 testApp

Finally we run GDB from a different directory (otherwise it will still find libTest.so):

cd /

gdb /home/testuser/libtest/testApp

Now we will try to set a breakpoint inside libTest.so (that will fail as /tmp/libTest.so is not initially loaded). Note how specifying set solib-search-path allows GDB load the symbols and set
a breakpoint:

(gdb) target remote deploy_machine:2000

Remote debugging using deploy_machine:2000

Reading symbols from /lib/ld-linux.so.2...

Reading symbols from /usr/lib/debug/lib/i386-linux-gnu/ld-2.15.so...done.

done.

Loaded symbols for /lib/ld-linux.so.2

(gdb) break main

Breakpoint 1 at 0x80484ed: file main.cpp, line 7.

(gdb) continue

Continuing.

Breakpoint 1, main () at main.cpp:7

7 printf("In main()\n");

(gdb) break test

Function "test" not defined.

Make breakpoint pending on future shared library load? (y or
) n

(gdb) info sharedlibrary 

warning: Could not load shared library symbols for /tmp/libTest.so.

Do you need "set solib-search-path" or "set sysroot"?

From To Syms Read Shared Object Library

0x0019b820 0x001b3b9f Yes /lib/ld-linux.so.2

No /tmp/libTest.so

0x004bcf10 0x005f15cc No /lib/i386-linux-gnu/libc.so.6

(gdb) set solib-search-path /home/testuser/libtest

Reading symbols from /home/testuser/libtest/libTest.so...done.

Loaded symbols for /home/testuser/libtest/libTest.so

Reading symbols from /lib/i386-linux-gnu/libc.so.6...

Reading symbols from /usr/lib/debug/lib/i386-linux-gnu/libc-2.15.so...done.

done.

Loaded symbols for /lib/i386-linux-gnu/libc.so.6

(gdb) info sharedlibrary 

From To Syms Read Shared Object Library

0x0019b820 0x001b3b9f Yes /lib/ld-linux.so.2

0x00f893a0 0x00f894c8 Yes /home/testuser/libtest/libTest.so

0x004bcf10 0x005f15cc Yes /lib/i386-linux-gnu/libc.so.6

(gdb) break func

Breakpoint 2 at 0xf8946e: file lib.cpp, line 5.

(gdb) continue

Continuing.

Breakpoint 2, func () at lib.cpp:5

5 printf("In func()\n");

(gdb) backtrace 

#0 func () at lib.cpp:5

#1 0x080484fe in main () at main.cpp:8

Compatibility with VisualGDB

VisualGDB automatically configures search paths using the set solib-search-path command when you debug your Linux or Android projects with Visual Studio. Nonetheless you can issue the command
manually as well using the GDB Session window.