@cindex dynamic symbol table
@kindex -E
@kindex --export-dynamic
+@kindex --no-export-dynamic
@item -E
@itemx --export-dynamic
-When creating a dynamically linked executable, add all symbols to the
-dynamic symbol table. The dynamic symbol table is the set of symbols
-which are visible from dynamic objects at run time.
+@itemx --no-export-dynamic
+When creating a dynamically linked executable, using the @option{-E}
+option or the @option{--export-dynamic} option causes the linker to add
+all symbols to the dynamic symbol table. The dynamic symbol table is the
+set of symbols which are visible from dynamic objects at run time.
-If you do not use this option, the dynamic symbol table will normally
-contain only those symbols which are referenced by some dynamic object
-mentioned in the link.
+If you do not use either of these options (or use the
+@option{--no-export-dynamic} option to restore the default behavior), the
+dynamic symbol table will normally contain only those symbols which are
+referenced by some dynamic object mentioned in the link.
If you use @code{dlopen} to load a dynamic object which needs to refer
back to the symbols defined by the program, rather than some other
be added to the dynamic symbol table if the output format supports it.
See the description of @samp{--dynamic-list}.
+Note that this option is specific to ELF targeted ports. PE targets
+support a similar function to export all symbols from a DLL or EXE; see
+the description of @samp{--export-all-symbols} below.
+
@ifclear SingleFormat
@cindex big-endian objects
@cindex endianness
Add the archive or object file specified by @var{namespec} to the
list of files to link. This option may be used any number of times.
If @var{namespec} is of the form @file{:@var{filename}}, @command{ld}
-will search the library path for a file called @var{filename}, otherise it
+will search the library path for a file called @var{filename}, otherwise it
will search the library path for a file called @file{lib@var{namespec}.a}.
On systems which support shared libraries, @command{ld} may also search for
in which they are specified on the command line. Directories specified
on the command line are searched before the default directories. All
@option{-L} options apply to all @option{-l} options, regardless of the
-order in which the options appear.
+order in which the options appear. @option{-L} options do not affect
+how @command{ld} searches for a linker script unless @option{-T}
+option is specified.
If @var{searchdir} begins with @code{=}, then the @code{=} will be replaced
by the @dfn{sysroot prefix}, a path specified when the linker is configured.
Specify the name of a version script to the linker. This is typically
used when creating shared libraries to specify additional information
about the version hierarchy for the library being created. This option
-is only meaningful on ELF platforms which support shared libraries.
-@xref{VERSION}.
+is only fully supported on ELF platforms which support shared libraries;
+see @ref{VERSION}. It is partially supported on PE platforms, which can
+use version scripts to filter symbol visibility in auto-export mode: any
+symbols marked @samp{local} in the version script will not be exported.
+@xref{WIN32}.
@kindex --warn-common
@cindex warnings, on combining symbols
@item --warn-shared-textrel
Warn if the linker adds a DT_TEXTREL to a shared object.
+@kindex --warn-alternate-em
+@item --warn-alternate-em
+Warn if an object has alternate ELF machine code.
+
@kindex --warn-unresolved-symbols
@item --warn-unresolved-symbols
If the linker is going to report an unresolved symbol (see the option
@var{which}.
[This option is specific to the i386 PE targeted port of the linker]
+The following options set flags in the @code{DllCharacteristics} field
+of the PE file header:
+[These options are specific to PE targeted ports of the linker]
+
+@kindex --dynamicbase
+@item --dynamicbase
+The image base address may be relocated using address space layout
+randomization (ASLR). This feature was introduced with MS Windows
+Vista for i386 PE targets.
+
+@kindex --forceinteg
+@item --forceinteg
+Code integrity checks are enforced.
+
+@kindex --nxcompat
+@item --nxcompat
+The image is compatible with the Data Execution Prevention.
+This feature was introduced with MS Windows XP SP2 for i386 PE targets.
+
+@kindex --no-isolation
+@item --no-isolation
+Although the image understands isolation, do not isolate the image.
+
+@kindex --no-seh
+@item --no-seh
+The image does not use SEH. No SE handler may be called from
+this image.
+
+@kindex --no-bind
+@item --no-bind
+Do not bind this image.
+
+@kindex --wdmdriver
+@item --wdmdriver
+The driver uses the MS Windows Driver Model.
+
+@kindex --tsaware
+@item --tsaware
+The image is Terminal Server aware.
+
@end table
@c man end
@smallexample
@group
@var{section} [@var{address}] [(@var{type})] :
- [AT(@var{lma})] [ALIGN(@var{section_align})] [SUBALIGN(@var{subsection_align})]
+ [AT(@var{lma})]
+ [ALIGN(@var{section_align})]
+ [SUBALIGN(@var{subsection_align})]
+ [@var{constraint}]
@{
@var{output-section-command}
@var{output-section-command}
aligned upward to the specified value.
Specifying @var{address} for a section will change the value of the
-location counter.
+location counter, provided that the section is non-empty. (Empty
+sections are ignored).
@node Input Section
@subsection Input Section Description
@cindex output section attributes
We showed above that the full description of an output section looked
like this:
+
@smallexample
@group
@var{section} [@var{address}] [(@var{type})] :
- [AT(@var{lma})] [ALIGN(@var{section_align})] [SUBALIGN(@var{subsection_align})]
+ [AT(@var{lma})]
+ [ALIGN(@var{section_align})]
+ [SUBALIGN(@var{subsection_align})]
+ [@var{constraint}]
@{
@var{output-section-command}
@var{output-section-command}
@} [>@var{region}] [AT>@var{lma_region}] [:@var{phdr} :@var{phdr} @dots{}] [=@var{fillexp}]
@end group
@end smallexample
+
We've already described @var{section}, @var{address}, and
@var{output-section-command}. In this section we will describe the
remaining section attributes.
* Output Section LMA:: Output section LMA
* Forced Output Alignment:: Forced Output Alignment
* Forced Input Alignment:: Forced Input Alignment
+* Output Section Constraint:: Output section constraint
* Output Section Region:: Output section region
* Output Section Phdr:: Output section phdr
* Output Section Fill:: Output section fill
SUBALIGN. The value specified overrides any alignment given by input
sections, whether larger or smaller.
+@node Output Section Constraint
+@subsubsection Output Section Constraint
+@kindex ONLY_IF_RO
+@kindex ONLY_IF_RW
+@cindex constraints on output sections
+You can specify that an output section should only be created if all
+of its input sections are read-only or all of its input sections are
+read-write by using the keyword @code{ONLY_IF_RO} and
+@code{ONLY_IF_RW} respectively.
+
@node Output Section Region
@subsubsection Output Section Region
@kindex >@var{region}
@menu
* Constants:: Constants
+* Symbolic Constants:: Symbolic constants
* Symbols:: Symbol Names
* Orphan Sections:: Orphan Sections
* Location Counter:: The Location Counter
Note - the @code{K} and @code{M} suffixes cannot be used in
conjunction with the base suffixes mentioned above.
+@node Symbolic Constants
+@subsection Symbolic Constants
+@cindex symbolic constants
+@kindex CONSTANT
+It is possible to refer to target specific constants via the use of
+the @code{CONSTANT(@var{name})} operator, where @var{name} is one of:
+
+@table @code
+@item MAXPAGESIZE
+@kindex MAXPAGESIZE
+The target's maximum page size.
+
+@item COMMONPAGESIZE
+@kindex COMMONPAGESIZE
+The target's default page size.
+@end table
+
+So for example:
+
+@smallexample
+ .text ALIGN (CONSTANT (MAXPAGESIZE)) : @{ *(.text) @}
+@end smallexample
+
+will create a text section aligned to the largest page boundary
+supported by the target.
+
@node Symbols
@subsection Symbol Names
@cindex symbol names
target subroutine is a leaf routine (that is, the target subroutine does
not itself call any subroutines).
+@cindex Cortex-A8 erratum workaround
+@kindex --fix-cortex-a8
+@kindex --no-fix-cortex-a8
+The @samp{--fix-cortex-a8} switch enables a link-time workaround for an erratum in certain Cortex-A8 processors. The workaround is enabled by default if you are targeting the ARM v7-A architecture profile. It can be enabled otherwise by specifying @samp{--fix-cortex-a8}, or disabled unconditionally by specifying @samp{--no-fix-cortex-a8}.
+
+The erratum only affects Thumb-2 code. Please contact ARM for further details.
+
@ifclear GENERIC
@lowersections
@end ifclear
@samp{--relax} enables the generation of trampolines that can access
the entire 32-bit address space. These trampolines are inserted at
section boundaries, so may not themselves be reachable if an input
-section exceeds 33M in size.
+section exceeds 33M in size. You may combine @samp{-r} and
+@samp{--relax} to add trampolines in a partial link. In that case
+both branches to undefined symbols and inter-section branches are also
+considered potentially out of range, and trampolines inserted.
@cindex PowerPC ELF32 options
@table @option
@item --exclude-symbols
@item --exclude-libs
@item --exclude-modules-for-implib
+@item --version-script
@end itemize
-If, however, @samp{--export-all-symbols} is not given explicitly on the
+When auto-export is in operation, @command{ld} will export all the non-local
+(global and common) symbols it finds in a DLL, with the exception of a few
+symbols known to belong to the system's runtime and libraries. As it will
+often not be desirable to export all of a DLL's symbols, which may include
+private functions that are not part of any public interface, the command-line
+options listed above may be used to filter symbols out from the list for
+exporting. The @samp{--output-def} option can be used in order to see the
+final list of exported symbols with all exclusions taken into effect.
+
+If @samp{--export-all-symbols} is not given explicitly on the
command line, then the default auto-export behavior will be @emph{disabled}
if either of the following are true:
As a GNU extension, weak symbols that do not specify an alternate symbol
are supported. If the symbol is undefined when linking, the symbol
uses a default value.
+
+@cindex aligned common symbols
+@item aligned common symbols
+As a GNU extension to the PE file format, it is possible to specify the
+desired alignment for a common symbol. This information is conveyed from
+the assembler or compiler to the linker by means of GNU-specific commands
+carried in the object file's @samp{.drectve} section, which are recognized
+by @command{ld} and respected when laying out the common symbols. Native
+tools will be able to process object files employing this GNU extension,
+but will fail to respect the alignment instructions, and may issue noisy
+warnings about unknown linker directives.
@end table
@ifclear GENERIC
projects / deliverable / binutils-gdb.git / blobdiff