Re: Possible Bug with "n" Flag of .section Directive

[Nick Clifton <nickc at redhat dot com>]

Hi Tracy,

> Given the following .section directive:
> .section foo_n, "n"
> 
> The objdump output gives:
> 
> foo_n.o:     file format coff-sparc
> 
> Sections:
> Idx Name          Size      VMA       LMA       File off  Algn
>   0 .text         00000000  00000000  00000000  00000000  2**3
>                   ALLOC, LOAD, CODE
>   1 .data         00000000  00000000  00000000  00000000  2**3
>                   ALLOC, LOAD, DATA
>   2 .bss          00000000  00000000  00000000  00000000  2**3
>                   ALLOC
>   3 foo_n         00000000  00000000  00000000  00000000  2**3
>                   ALLOC, LOAD
> 
> The documentation states that the "n" flag means that the section is not 
> loaded.  The assembler appears to be setting the section's flags correctly 
> in the object file, but when objdump gets ahold of it, it changes the 
> flags to be ALLOC, LOAD.  It appears that this is happening in the 
> function styp_to_sec_flags in coffgen.c.  Is this a bug?

Actually I think that you will find that the assembler is setting the
ALLOC and LOAD bits and that objdump is in fact displaying the correct
information.

The reason for this behavior is that the "n" flag removes an
attribute from the section, rather than setting an attribute.  The
code in the assembler that parses the .section pseudo op
(obj_coff_section in gas/config/obj-coff.c) starts by setting all the
section flags to zero and then parsing each of the flags in turn.  If
no flags were set by the .section directive, then the default
attributes are used instead.  In this case the default flags are ALLOC
and LOAD.  Since the "n" attribute doe not set a flag, but removes
it, the code thinks that no attributes have been set and so the
defaults are used.

The solution is to use the "b" attribute instead of the "n"
attribute.  This will give you an ALLOC'able section which is not
LOAD'able, which is presumably what you want.

Cheers
        Nick