Re: "Cannot access memory at address 0x175f80"

[Andrew Greenlaw <andrewg@agere.com>]

    I was specifying add-symbol-file, because when I start "orange", 
none of the symbols from "apple" are accessible.  In DDD, the source 
code for Apple's files don't even appear in the "open source" menu.  The 
only 2 ways to make those files appear are 1) to run the program once, 
then set breakpoints, then re-run, or 2) use the add-symbol-file 
command.  I admit I wasn't using it in an informed manner, but it worked 
for the other symbols.

    I tried a little experiment:  I started gdb, used the 
add-symbol-file command, then entered "break nc_signal_raised".  It said 
"Cannot access memory at address 0x175f9c".  I then exited gdb, started 
over, and this time, instead of add-symbol-file, ran the program.  when 
the program exitted, I typed "break nc_signal_raised", It said 
"Breakpoint 1 at 0x40fb2f9f: file /sopt/ldv-dev/tools/src/main.cc, line 
8.".  So that was part of the problem.

    Now the bad news.  If I try to re-run, this particular breakpoint 
can't be inserted.  After that encouraging message above, I hit the 
"run" button in ddd, and got:

(gdb) run snap1
(no debugging symbols found)...Error in re-setting breakpoint 1:
Function "nc_signal_raised" not defined.
Error in re-setting breakpoint 1:
Function "nc_signal_raised" not defined.
Error in re-setting breakpoint 1:
Function "nc_signal_raised" not defined.
Error in re-setting breakpoint 1:
Function "nc_signal_raised" not defined.
Error in re-setting breakpoint 1:
Function "nc_signal_raised" not defined.
Error in re-setting breakpoint 1:
Function "nc_signal_raised" not defined.
Error in re-setting breakpoint 1:
Function "nc_signal_raised" not defined.
Error in re-setting breakpoint 1:
Function "nc_signal_raised" not defined.
Error in re-setting breakpoint 1:
Function "nc_signal_raised" not defined.
ncsim: 05.00-s005: (c) Copyright 1995-2003 Cadence Design Systems, Inc.
ncsim: *W,DLNOHV: Unable to find an 'hdl.var' file to load in.
Error in re-setting breakpoint 1:
Function "nc_signal_raised" not defined.
Error in re-setting breakpoint 1:
Function "nc_signal_raised" not defined.
Error in re-setting breakpoint 1:
Function "nc_signal_raised" not defined.
Error in re-setting breakpoint 1:
Function "nc_signal_raised" not defined.
Error in re-setting breakpoint 1:
Function "nc_signal_raised" not defined.
Error in re-setting breakpoint 1:
Function "nc_signal_raised" not defined.

    Any Ideas?

Daniel Jacobowitz wrote:

>On Fri, Sep 26, 2003 at 01:40:16PM -0400, Andrew Greenlaw wrote:
>  
>
>> Hi.  I'm debugging a C++ tool (called apple) that's loaded as a 
>>dynamic library into a C - or C++ program (called orange) .  Apple is 
>>compiled with g++ 3.3.1, binutils 2.14, and debugging symbols are 
>>enabled.  Orange is a big unknown (meaning:  I don't know how it was 
>>compiled) and it has no debugging symbols.  The gdb version is 5.3
>>
>>   Here are the flags used to compile Apple:
>># -gdwarf-2 -g3 used to enable stepping through macro execution under 
>>gdb 5.3  The explanation's under gdb 5.3 release notes.
>>   Compile:g++  -std=c++98 -Wall -DLINUX -gdwarf-2 -g3      -D__USE_GNU 
>>-D_GNU_SOURCE -fPIC file_name.cpp
>>
>>
>>   Link:
>>   g++ -shared $(LIBS) $(OBJSCHEF)  $(PLIOBJSVCS_PLI) 
>>InterfaceObjectVCS_PLI.o -o $@    -lc   gdwarf-2 -g3 -fPIC
>>g++  -MD -std=c++98  -shared -lc -gdwarf-2 -g3  -fPIC <object files>  -o 
>>libapple.so   
>>
>>   When I go to debug apple, I run "gdb <program name>", then use the 
>>"add-symbol-file <apple's path & filename> -readnow" gdb comman to load 
>>the symbols from apple.  From there, I can set breakpoints in C++ class 
>>methods, no problem.  But, there is 1 function (so, non-OO code), where 
>>if I try to set a breakpoint, I get the following:
>>
>>   (gdb) break nc_signal_raised
>>Cannot access memory at address 0x175f80
>>
>>   If I do an "nm" on the library, I get:
>>   00175f80 T nc_signal_raised
>>
>>   Indicating that the address read by gdb is correct.
>>    
>>
>
>Unlikely, since the library is not loaded at a base address of 0.
>
>  
>
>>   On a related, but less important note, when use ddd to debug & go to 
>>a source file, I always get:  "<src_file_name>" is at address 0x10f5f0 
>><part_of_src_file_name> but contains no code.
>>
>>   And yet I can set breakpoints or step through the code.  What's 
>>going on?
>>
>>   Any help you can offer will be appreciated.  I've been working on 
>>this for 2 weeks, read every posting or piece of documentation I can 
>>find.  I'm at my wits' end!
>>    
>>
>
>Why are you using add-symbol-file?  Is the loader not done as a dlopen,
>i.e. are you dealing with something that has its own dynamic loader? 
>If it's dlopen'd, gdb should automatically handle it.
>
>It seems unlikely that add-symbol-file without specifying a text offset
>is right, too.
>
>  
>

-- 
          Andrew Greenlaw, Advanced Verification Group
          Agere Systems of Ottawa, ON.  Intranet page:  http://ottawa/~andrewg/
          E-mail:  andrewg@agere.com, Phone: (613)768-8738, Fax:  (768)768-8710
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