Empty section removal has messed up MIPS gdb

Empty section removal has messed up MIPS gdb

[Daniel Jacobowitz]

GCC used to leave a message for the debugger in the form of an empty
section:

      /* Generate a special section to describe the ABI switches used to
         produce the resultant binary.  This used to be done by the assembler
         setting bits in the ELF header's flags field, but we have run out of
         bits.  GDB needs this information in order to be able to correctly
         debug these binaries.  See the function mips_gdbarch_init() in
         gdb/mips-tdep.c.  This is unnecessary for the IRIX 5/6 ABIs and
         causes unnecessary IRIX 6 ld warnings.  */

The emitted bits were simply:

	.section .mdebug.abi64
	.previous

The sections are now stripped.  I don't want to put contents in them and
waste object file space unless it's absolutely necessary.  How should I
cajole ld into leaving them?

-- 
Daniel Jacobowitz
CodeSourcery, LLC

Re: Empty section removal has messed up MIPS gdb

[H. J. Lu]

On Wed, Apr 20, 2005 at 05:35:33PM -0400, Daniel Jacobowitz wrote:
> GCC used to leave a message for the debugger in the form of an empty
> section:
> 
>       /* Generate a special section to describe the ABI switches used to
>          produce the resultant binary.  This used to be done by the assembler
>          setting bits in the ELF header's flags field, but we have run out of
>          bits.  GDB needs this information in order to be able to correctly
>          debug these binaries.  See the function mips_gdbarch_init() in
>          gdb/mips-tdep.c.  This is unnecessary for the IRIX 5/6 ABIs and
>          causes unnecessary IRIX 6 ld warnings.  */
> 
> The emitted bits were simply:
> 
> 	.section .mdebug.abi64
> 	.previous
> 
> The sections are now stripped.  I don't want to put contents in them and
> waste object file space unless it's absolutely necessary.  How should I
> cajole ld into leaving them?
> 

Mark it KEEP?


H.J.

Re: Empty section removal has messed up MIPS gdb

[Daniel Jacobowitz]

On Wed, Apr 20, 2005 at 02:53:17PM -0700, H. J. Lu wrote:
> On Wed, Apr 20, 2005 at 05:35:33PM -0400, Daniel Jacobowitz wrote:
> > GCC used to leave a message for the debugger in the form of an empty
> > section:
> > 
> >       /* Generate a special section to describe the ABI switches used to
> >          produce the resultant binary.  This used to be done by the assembler
> >          setting bits in the ELF header's flags field, but we have run out of
> >          bits.  GDB needs this information in order to be able to correctly
> >          debug these binaries.  See the function mips_gdbarch_init() in
> >          gdb/mips-tdep.c.  This is unnecessary for the IRIX 5/6 ABIs and
> >          causes unnecessary IRIX 6 ld warnings.  */
> > 
> > The emitted bits were simply:
> > 
> > 	.section .mdebug.abi64
> > 	.previous
> > 
> > The sections are now stripped.  I don't want to put contents in them and
> > waste object file space unless it's absolutely necessary.  How should I
> > cajole ld into leaving them?
> > 
> 
> Mark it KEEP?

This is something that has to be done in the linker, right?  i.e. the
linker would also need to know about this convention.

-- 
Daniel Jacobowitz
CodeSourcery, LLC

Re: Empty section removal has messed up MIPS gdb

[H. J. Lu]

On Wed, Apr 20, 2005 at 05:57:46PM -0400, Daniel Jacobowitz wrote:
> On Wed, Apr 20, 2005 at 02:53:17PM -0700, H. J. Lu wrote:
> > On Wed, Apr 20, 2005 at 05:35:33PM -0400, Daniel Jacobowitz wrote:
> > > GCC used to leave a message for the debugger in the form of an empty
> > > section:
> > > 
> > >       /* Generate a special section to describe the ABI switches used to
> > >          produce the resultant binary.  This used to be done by the assembler
> > >          setting bits in the ELF header's flags field, but we have run out of
> > >          bits.  GDB needs this information in order to be able to correctly
> > >          debug these binaries.  See the function mips_gdbarch_init() in
> > >          gdb/mips-tdep.c.  This is unnecessary for the IRIX 5/6 ABIs and
> > >          causes unnecessary IRIX 6 ld warnings.  */
> > > 
> > > The emitted bits were simply:
> > > 
> > > 	.section .mdebug.abi64
> > > 	.previous
> > > 
> > > The sections are now stripped.  I don't want to put contents in them and
> > > waste object file space unless it's absolutely necessary.  How should I
> > > cajole ld into leaving them?
> > > 
> > 
> > Mark it KEEP?
> 
> This is something that has to be done in the linker, right?  i.e. the
> linker would also need to know about this convention.
> 

It is done in linker script:

[hjl@gnu scripttempl]$ grep KEEP elf.sc
    KEEP (*crtbegin*.o(.ctors))
    KEEP (*(EXCLUDE_FILE (*crtend*.o $OTHER_EXCLUDE_FILES) .ctors))
    KEEP (*(SORT(.ctors.*)))
    KEEP (*(.ctors))
    KEEP (*crtbegin*.o(.dtors))
    KEEP (*(EXCLUDE_FILE (*crtend*.o $OTHER_EXCLUDE_FILES) .dtors))
    KEEP (*(SORT(.dtors.*)))
    KEEP (*(.dtors))
    KEEP (*(.init))
    KEEP (*(.text.*personality*))
    KEEP (*(.fini))
  .eh_frame     ${RELOCATING-0} : ONLY_IF_RO { KEEP (*(.eh_frame)) }
  .gcc_except_table ${RELOCATING-0} : ONLY_IF_RO { KEEP
(*(.gcc_except_table)) *(.gcc_except_table.*) }
  .eh_frame     ${RELOCATING-0} : ONLY_IF_RW { KEEP (*(.eh_frame)) }
  .gcc_except_table ${RELOCATING-0} : ONLY_IF_RW { KEEP
(*(.gcc_except_table)) *(.gcc_except_table.*) }
  .preinit_array   ${RELOCATING-0} : { KEEP (*(.preinit_array)) }
  .init_array   ${RELOCATING-0} : { KEEP (*(.init_array)) }
  .fini_array   ${RELOCATING-0} : { KEEP (*(.fini_array)) }
  .jcr          ${RELOCATING-0} : { KEEP (*(.jcr)) }
    KEEP (*(.gnu.linkonce.d.*personality*))

You can do it for .mdebug.abi64.


H.J.

Re: Empty section removal has messed up MIPS gdb

[Eric Christopher]

> You can do it for .mdebug.abi64.

As a note if Daniel is going to do the patch then please do it
for .gcc_compiled_long[32,64] as well :)

If you're too busy to do it lemme know and I will.

-eric