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[Bug binutils/21429] objdump -d generate not good value in comment


From: nickc at redhat dot com
Subject: [Bug binutils/21429] objdump -d generate not good value in comment
Date: Tue, 02 May 2017 15:45:54 +0000

https://sourceware.org/bugzilla/show_bug.cgi?id=21429

Nick Clifton <nickc at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
                 CC|                            |nickc at redhat dot com
         Resolution|---                         |INVALID

--- Comment #1 from Nick Clifton <nickc at redhat dot com> ---
Hi Linyu,

> when i use objdump in binutils 2.26 to dump a ARM image, 
> I saw value in comment is not good, some are errors.
> 
> check below asm code,
>   c009a8:     e3e03afe        mvn     r3, #1040384    ; 0xfe000
>   c009ac:     e50320ef        str     r2, [r3, #-239] ; 0xffffff11
>   c009b0:     e50320eb        str     r2, [r3, #-235] ; 0xffffff15
>   c009b4:     e50320e7        str     r2, [r3, #-231] ; 0xffffff19
>   c009b8:     e50320e3        str     r2, [r3, #-227] ; 0xffffff1d 

Ah - no - the comments are correct.  It is just that they are not telling
you the result of the address computation, they are telling you the hex
value of the constants encoded in the instructions.  The intent is that 
knowing the hex value may be useful in understanding the purpose of the
instruction.

The reason that the comment does not show the full address computation is
that the address cannot be known.  Just because the instructions occur in
a sequence it does not mean that one of them might be the target of a 
branch.  So the contents of the R3 register cannot be known reliably.

Cheers
  Nick

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