HP-UX Reference (11i v2 04/09) - 1 User Commands A-M (vol 1)

l
ld_pa(1) ld_pa(1)
(For PA-RISC Systems)
Defaults
Unless otherwise directed, ld names its output
a.out. The -o option overrides this. Executable out-
put files are of type
SHARE_MAGIC. The default state of
-a is to search shared libraries if available,
archive libraries otherwise. The default bind behavior is
deferred.
The default value of the
-Z/-z
option is -Z.
For 64-bit mode,
+std is on by default.
Incremental linking with ld (64-bit Mode ONLY)
In the edit-compile-link-debug development cycle, link time is a significant component. The incremental
linker (available through the
+ild and +ildrelink options) can reduce the link time by taking advan-
tage of the fact that you can reuse most of the previous version of the program and that the unchanged
object files do not need to be processed. The incremental linker allows you to insert object code into an
output file (executable or shared library) that you created earlier, without relinking the unmodified object
files. The time required to relink after the initial incremental link depends on the number of modules you
modify.
The linker performs the following different modes of linking:
• normal link: the default operation mode in which the linker links all modules.
• initial incremental link: the mode entered when you request an incremental link, but the output
module created by the incremental linker does not exist, or it exists but the incremental linker is
unable to perform an incremental update.
• incremental link: the mode entered when you request an incremental link, an output module
created by the incremental linker exists, and the incremental linker does not require an initial
incremental link.
Incremental links are usually much faster than regular links. On the initial link, the incremental linker
requires about the same amount of time that a normal link process requires, but subsequent incremental
links can be much faster than a normal link. A change in one object file in a moderate size link (tens of
files, several megabytes total) normally is about 10 times faster than a regular
ld link. The incremental
linker perform as many incremental links as allocated padding space and other constrains permit. The
cost of the reduced link time is an increase in the size of the executable or shared library.
The incremental linker allocates padding space for all components of the output file. Padding makes
modules larger than those modules linked by
ld. As object files increase in size during successive incre-
mental links, the incremental linker can exhaust the available padding. If this occurs, it displays a warn-
ing message and does a complete initial incremental link of the module. When an object file changes, the
incremental linker not only replaces the content of that file in the executable or shared library being
linked, but also adjusts references to all symbols defined in the object file and referenced by other objects.
This is done by looking at relocation records saved in the incrementally linked executable or shared
library.
On the initial incremental link, the linker processes the input object files and libraries in the same way as
the normal link. In addition to the normal linking process, the incremental linker saves information
about object files, global symbols, and relocations, and pads sections in the output file for expansion. On
subsequent incremental links, the linker uses timestamps and file sizes to determine which object files
have changed, and updates those modules.
Under certain conditions, the incremental linker cannot perform incremental links. When this occurs, the
incremental linker automatically performs an initial incremental link to restore the process. In the fol-
lowing situations, the linker automatically performs an initial incremental link of the output file:
• Changed linker command line, where the linker command line does not match the command line
stored in the output file. (With the exceptions of the verbose and tracing options)
• Any of the padding spaces have been exhausted.
• Modules have been modified by the
ld -s or ld -x options or tools (for example, strip(1)). The
incremental linking requires the parts of the output load module which are stripped out with these
options.
• Incompatible incremental linker version, when you run a new version of the incremental linker on
an executable created by an older version.
• New working directory, where the incremental linker performs an initial incremental link if current
directory changes.
HP-UX 11i Version 2: September 2004 − 15 − Hewlett-Packard Company Section 1−−483