[Bug binutils/152] dwarf2 + special link technique causes "DW_FORM_strp pointing outside of .debug_str section" in GDB

[nickc at redhat dot com]

------- Additional Comments From nickc at redhat dot com  2004-05-24 16:37 
-------
Subject: Re:  New: dwarf2 + special link technique causes
 "DW_FORM_strp pointing outside of .debug_str section" in GDB

Hi Bart,


> main: main.o bios.o
>         ld $^ -o $@
> 
> bios.o: bios.S
>         as --gdwarf2 bios.S -o tmp.o
>         ld -Ttext 0 -e 0 tmp.o -o bios.o

The problem here is that you are taking a fully linked executable 
(bios.o)(1) with its own, already setup debug info, and you are 
attempting to link it into another executable (main).  The linker will 
merge the sections containing the debug information, but because there 
are no relocations left in bios.o it will not be able to fix up the 
offsets into the abbreviations table and hence you will get the errors 
you encountered.

This is also why using STABS or no debugging works.  With different (or 
no) debug sections in your bios.o executable there is no problem merging 
it into the main program.  You could use the -r linker switch to avoid 
this problem, but as you already know this would stop the -Ttext 0 and 
-e 0 switches from performing their tasks.

One simple solution is to reorder the final link so that bios.o is 
linked in first.  This way its (already relocated) debug information 
will be the first entries in the debug sections and the debug 
information from main.o (which can be relocated) will be appended to the 
end of the sections.  ie change your makefile like this:

- main: main.o bios.o
+ main: bios.o main.o

Cheers
   Nick

(1) Just because the file is called "bios.o" does not mean that it is an 
object file.  You used the -o option to the linker to override the 
default output name (a.out) but you still created an executable file.


-- 


http://sources.redhat.com/bugzilla/show_bug.cgi?id=152

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