HP-UX Reference (11i v3 07/02) - 1 User Commands A-M (vol 1)

l
ld_ia(1)
Integrity Systems Only
ld_ia(1)
To debug the load modules compiled with
+objdebug option, the HP WDB debugger must have access to
the object files. (Note that for object files built with the
-r option, the individual object files must be avail-
able to the debugger.) If you move the object files, use HP WDB’s
objdir command to specify the loca-
tion of these objects.
The
+noobjdebug compiler option causes the debug information to be copied over to the output file.
+objdebug is the compile-time default.
If the linker detects any object files that were compiled with the
+objdebug option, it leaves the debug
information in those files. Any object files not compiled with
+objdebug have their debug information
copied into the output file.
You can use the
+noobjdebug option at link time to continue to place the debug information into the
output file, even if some objects were compiled with
+objdebug.
Incremental linking
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 out-
put 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 warning
message and does a complete initial incremental link of the module.
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 subse-
quent incremental links, the linker uses timestamps 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 follow-
ing 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)).
• 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.
532 Hewlett-Packard Company − 15 − HP-UX 11i Version 3: February 2007