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Re: PATCH: Fix empty sections with alignment
On Tue, Sep 27, 2005 at 08:04:05AM -0700, H. J. Lu wrote:
> >
> > Instead, I think we need some linker script construct that allows us to
> > increase the alignment of an output section over that specified by its
> > input sections, other than using ALIGN() as the address. Perhaps an
> > ALIGN() after the semicolon. lang_enter_output_section_statement
> > already supports an output section alignment.
>
> I will look into it.
>
Here is the patch to allow ALIGN to be used to force output section
alignment.
H.J.
----
2005-09-27 H.J. Lu <hongjiu.lu@intel.com>
* ld.texinfo (ALIGN): Document it as forcing output section
alignment.
* ldgram.y (ALIGN): Support it for forcing output section
alignment.
--- ld/ld.texinfo.align 2005-09-26 13:12:55.000000000 -0700
+++ ld/ld.texinfo 2005-09-27 10:11:16.000000000 -0700
@@ -3067,7 +3067,7 @@ The full description of an output sectio
@smallexample
@group
@var{section} [@var{address}] [(@var{type})] :
- [AT(@var{lma})] [SUBALIGN(@var{subsection_align})]
+ [AT(@var{lma})] [ALIGN(@var{section_align})] [SUBALIGN(@var{subsection_align})]
@{
@var{output-section-command}
@var{output-section-command}
@@ -3643,7 +3643,7 @@ like this:
@smallexample
@group
@var{section} [@var{address}] [(@var{type})] :
- [AT(@var{lma})] [SUBALIGN(@var{subsection_align})]
+ [AT(@var{lma})] [ALIGN(@var{section_align})] [SUBALIGN(@var{subsection_align})]
@{
@var{output-section-command}
@var{output-section-command}
@@ -3658,6 +3658,7 @@ remaining section attributes.
@menu
* Output Section Type:: Output section type
* Output Section LMA:: Output section LMA
+* Forced Output Alignment:: Forced Output Alignment
* Forced Input Alignment:: Forced Input Alignment
* Output Section Region:: Output section region
* Output Section Phdr:: Output section phdr
@@ -3771,6 +3772,15 @@ for (dst = &_bstart; dst< &_bend; dst++)
@end group
@end smallexample
+@node Forced Output Alignment
+@subsubsection Forced Output Alignment
+@kindex ALIGN(@var{section_align})
+@cindex forcing output section alignment
+@cindex output section alignment
+You can force an output section alignment by using ALIGN. The value
+specified overrides any alignment given by input sections, whether
+larger or smaller.
+
@node Forced Input Alignment
@subsubsection Forced Input Alignment
@kindex SUBALIGN(@var{subsection_align})
--- ld/ldgram.y.align 2005-09-26 13:12:55.000000000 -0700
+++ ld/ldgram.y 2005-09-27 10:04:14.000000000 -0700
@@ -92,7 +92,7 @@ static int error_index;
}
%type <etree> exp opt_exp_with_type mustbe_exp opt_at phdr_type phdr_val
-%type <etree> opt_exp_without_type opt_subalign
+%type <etree> opt_exp_without_type opt_subalign opt_align
%type <fill> fill_opt fill_exp
%type <name_list> exclude_name_list
%type <wildcard_list> file_NAME_list
@@ -892,6 +892,11 @@ opt_at:
| { $$ = 0; }
;
+opt_align:
+ ALIGN_K '(' exp ')' { $$ = $3; }
+ | { $$ = 0; }
+ ;
+
opt_subalign:
SUBALIGN '(' exp ')' { $$ = $3; }
| { $$ = 0; }
@@ -907,20 +912,21 @@ sect_constraint:
section: NAME { ldlex_expression(); }
opt_exp_with_type
opt_at
+ opt_align
opt_subalign { ldlex_popstate (); ldlex_script (); }
sect_constraint
'{'
{
lang_enter_output_section_statement($1, $3,
sectype,
- 0, $5, $4, $7);
+ $5, $6, $4, $8);
}
statement_list_opt
'}' { ldlex_popstate (); ldlex_expression (); }
memspec_opt memspec_at_opt phdr_opt fill_opt
{
ldlex_popstate ();
- lang_leave_output_section_statement ($16, $13, $15, $14);
+ lang_leave_output_section_statement ($17, $14, $16, $15);
}
opt_comma
{}