diff options
| author | Alan Modra <amodra@gmail.com> | 2014-01-22 11:43:03 +1030 |
|---|---|---|
| committer | Alan Modra <amodra@gmail.com> | 2014-01-22 11:58:29 +1030 |
| commit | 2edab91c10dcae30a93ce7d9f8088b8b33ee55eb (patch) | |
| tree | 883bbadffed39aea4c78262946e12a35660b5bbe /ld/ld.texinfo | |
| parent | 4584ec12076e088cf36965b88ef8710ca85491f9 (diff) | |
| download | gdb-2edab91c10dcae30a93ce7d9f8088b8b33ee55eb.zip gdb-2edab91c10dcae30a93ce7d9f8088b8b33ee55eb.tar.gz gdb-2edab91c10dcae30a93ce7d9f8088b8b33ee55eb.tar.bz2 | |
Make assignments to dot keep an empty output section.
An assignment to dot in an output section that allocates space of
course keeps the output section. Here, I'm changing the behaviour for
assignments that don't allocate space. The idea is not so much to
allow people to force output of an empty section with ". = .", but
to fix cases where an otherwise empty section has padding added by an
alignment expression that changes with relaxation or .eh_frame
editing. Such a section might have zero size before relaxation and so
be stripped incorrectly.
ld/
* ld.texinfo (Output Section Discarding): Mention assigning to dot
as a way of keeping otherwise empty sections.
* ldexp.c (is_dot, is_value, is_sym_value, is_dot_ne_0,
is_dot_plus_0, is_align_conditional): New predicates.
(exp_fold_tree_1): Set SEC_KEEP when assigning to dot inside an
output section, except for some special cases.
* scripttempl/elfmicroblaze.sc: Use canonical form to align at
end of .heap and .stack.
ld/testsuite/
* ld-shared/elf-offset.ld: Align end of .bss with canonical form
of ALIGN that allows an empty .bss to be removed.
* ld-arm/arm-dyn.ld: Likewise.
* ld-arm/arm-lib.ld: Likewise.
* ld-elfvsb/elf-offset.ld: Likewise.
* ld-mips-elf/mips-dyn.ld: Likewise.
* ld-mips-elf/mips-lib.ld: Likewise.
* ld-arm/arm-no-rel-plt.ld: Remove duplicate ALIGN.
* ld-powerpc/vle-multiseg-1.ld: Remove ALIGN at start of section.
ALIGN address of section instead.
* ld-powerpc/vle-multiseg-2.ld: Likewise.
* ld-powerpc/vle-multiseg-3.ld: Likewise.
* ld-powerpc/vle-multiseg-4.ld: Likewise.
* ld-powerpc/vle-multiseg-6.ld: Likewise.
* ld-scripts/empty-aligned.d: Check section headers not program
headers. Remove xfail and notarget.
* ld-scripts/empty-aligned.t: Use canonical ALIGN for end of .text2.
Diffstat (limited to 'ld/ld.texinfo')
| -rw-r--r-- | ld/ld.texinfo | 13 |
1 files changed, 9 insertions, 4 deletions
diff --git a/ld/ld.texinfo b/ld/ld.texinfo index ae3d568..a8e5ea6 100644 --- a/ld/ld.texinfo +++ b/ld/ld.texinfo @@ -4406,9 +4406,9 @@ scripts. @cindex discarding sections @cindex sections, discarding @cindex removing sections -The linker will not create output sections with no contents. This is -for convenience when referring to input sections that may or may not -be present in any of the input files. For example: +The linker will not normally create output sections with no contents. +This is for convenience when referring to input sections that may or +may not be present in any of the input files. For example: @smallexample .foo : @{ *(.foo) @} @end smallexample @@ -4416,7 +4416,12 @@ be present in any of the input files. For example: will only create a @samp{.foo} section in the output file if there is a @samp{.foo} section in at least one input file, and if the input sections are not all empty. Other link script directives that allocate -space in an output section will also create the output section. +space in an output section will also create the output section. So +too will assignments to dot even if the assignment does not create +space, except for @samp{. = 0}, @samp{. = . + 0}, @samp{. = sym}, +@samp{. = . + sym} and @samp{. = ALIGN (. != 0, expr, 1)} when +@samp{sym} is an absolute symbol of value 0 defined in the script. +This allows you to force output of an empty section with @samp{. = .}. The linker will ignore address assignments (@pxref{Output Section Address}) on discarded output sections, except when the linker script defines |