1 <!doctype linuxdoc system>
4 <title>ld65 Users Guide
5 <author>Ullrich von Bassewitz, <htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">
6 <date>02.12.2000, 02.10.2001
9 The ld65 linker combines object files into an executable file. ld65 is highly
10 configurable and uses configuration files for high flexibility.
13 <!-- Table of contents -->
16 <!-- Begin the document -->
20 The ld65 linker combines several object modules created by the ca65
21 assembler, producing an executable file. The object modules may be read
22 from a library created by the ar65 archiver (this is somewhat faster and
23 more convenient). The linker was designed to be as flexible as possible.
24 It complements the features that are built into the ca65 macroassembler:
28 <item> Accept any number of segments to form an executable module.
30 <item> Resolve arbitrary expressions stored in the object files.
32 <item> In case of errors, use the meta information stored in the object files
33 to produce helpful error messages. In case of undefined symbols,
34 expression range errors, or symbol type mismatches, ld65 is able to
35 tell you the exact location in the original assembler source, where
36 the symbol was referenced.
38 <item> Flexible output. The output of ld65 is highly configurable by a config
39 file. More common platforms are supported by builtin configurations
40 that may be activated by naming the target system. The output
41 generation was designed with different output formats in mind, so
42 adding other formats shouldn't be a great problem.
50 <sect1>Command line option overview<p>
52 The linker is called as follows:
55 ---------------------------------------------------------------------------
56 Usage: ld65 [options] module ...
58 -C name Use linker config file
59 -L path Specify a library search path
60 -Ln name Create a VICE label file
61 -Lp Mark write protected segments as such (VICE)
62 -S addr Set the default start address
63 -V Print the linker version
65 -m name Create a map file
66 -o name Name the default output file
67 -t sys Set the target system
72 --cfg-path path Specify a config file search path
73 --config name Use linker config file
74 --dump-config name Dump a builtin configuration
75 --help Help (this text)
76 --lib file Link this library
77 --lib-path path Specify a library search path
78 --mapfile name Create a map file
79 --module-id id Specify a module id
80 --obj file Link this object file
81 --obj-path path Specify an object file search path
82 --start-addr addr Set the default start address
83 --target sys Set the target system
84 --version Print the linker version
85 ---------------------------------------------------------------------------
89 <sect1>Command line options in detail<p>
91 Here is a description of all the command line options:
95 <tag><tt>-h, --help</tt></tag>
97 Print the short option summary shown above.
100 <label id="option-m">
101 <tag><tt>-m name, --mapfile name</tt></tag>
103 This option (which needs an argument that will used as a filename for
104 the generated map file) will cause the linker to generate a map file.
105 The map file does contain a detailed overview over the modules used, the
106 sizes for the different segments, and a table containing exported
110 <label id="option-o">
111 <tag><tt>-o name</tt></tag>
113 The -o switch is used to give the name of the default output file.
114 Depending on your output configuration, this name may NOT be used as
115 name for the output file. However, for the builtin configurations, this
116 name is used for the output file name.
119 <label id="option-t">
120 <tag><tt>-t sys, --target sys</tt></tag>
122 The argument for the -t switch is the name of the target system. Since this
123 switch will activate a builtin configuration, it may not be used together
124 with the <tt><ref id="option-C" name="-C"></tt> option. The following target
125 systems are currently supported:
132 <item>c16 (works also for the c116 with memory up to 32K)
136 <item>cbm510 (CBM-II series with 40 column video)
137 <item>cbm610 (all CBM series-II computers with 80 column video)
138 <item>pet (all CBM PET systems except the 2001)
145 There are a few more targets defined but neither of them is actually
149 <label id="option-v">
150 <tag><tt>-v, --verbose</tt></tag>
152 Using the -v option, you may enable more output that may help you to
153 locate problems. If an undefined symbol is encountered, -v causes the
154 linker to print a detailed list of the references (that is, source file
155 and line) for this symbol.
158 <tag><tt>-vm</tt></tag>
160 Must be used in conjunction with <tt><ref id="option-m" name="-m"></tt>
161 (generate map file). Normally the map file will not include empty segments
162 and sections, or unreferenced symbols. Using this option, you can force the
163 linker to include all this information into the map file.
166 <label id="option-C">
167 <tag><tt>-C</tt></tag>
169 This gives the name of an output config file to use. See section 4 for more
170 information about config files. -C may not be used together with <tt><ref
171 id="option-t" name="-t"></tt>.
174 <label id="option--lib-path">
175 <tag><tt>-L path, --lib-path path</tt></tag>
177 Specify a library search path. This option may be used more than once. It
178 adds a directory to the search path for library files. Libraries specified
179 without a path are searched in current directory, in the directory given in
180 the <tt/LD65_LIB/ environment variable, and in the list of directories
181 specified using <tt/--lib-path/.
184 <tag><tt>-Ln</tt></tag>
186 This option allows you to create a file that contains all global labels and
187 may be loaded into VICE emulator using the <tt/ll/ (load label) command. You
188 may use this to debug your code with VICE. Note: Older versions had some
189 bugs in the label code. If you have problems, please get the latest VICE
193 <tag><tt>-Lp</tt></tag>
198 <label id="option-S">
199 <tag><tt>-S addr, --start-addr addr</tt></tag>
201 Using -S you may define the default starting address. If and how this
202 address is used depends on the config file in use. For the builtin
203 configurations, only the "none" system honors an explicit start address,
204 all other builtin config provide their own.
207 <tag><tt>-V, --version</tt></tag>
209 This option print the version number of the linker. If you send any
210 suggestions or bugfixes, please include this number.
213 <label id="option--cfg-path">
214 <tag><tt>--cfg-path path</tt></tag>
216 Specify a config file search path. This option may be used more than once.
217 It adds a directory to the search path for config files. A config file given
218 with the <tt><ref id="option-C" name="-C"></tt> option that has no path in
219 its name is searched in the current directory, in the directory given in the
220 <tt/LD65_CFG/ environment variable, and in the list of directories specified
221 using <tt/--cfg-path/.
224 <tag><tt>--lib file</tt></tag>
226 Links a library to the output. Use this command line option instead of just
227 naming the library file, if the linker is not able to determine the file
228 type because of an unusual extension.
231 <tag><tt>--obj file</tt></tag>
233 Links an object file to the output. Use this command line option instead
234 of just naming the object file, if the linker is not able to determine the
235 file type because of an unusual extension.
238 <label id="option--obj-path">
239 <tag><tt>--obj-path path</tt></tag>
241 Specify an object file search path. This option may be used more than once.
242 It adds a directory to the search path for object files. An object file
243 passed to the linker that has no path in its name is searched in current
244 directory, in the directory given in the <tt/LD65_OBJ/ environment variable,
245 and in the list of directories specified using <tt/--obj-path/.
251 <sect>Search paths<p>
253 Starting with version 2.10 there are now several search paths for files needed
254 by the linker: One for libraries, one for object files and one for config
258 <sect1>Library search path<p>
260 The library search path contains in this order:
263 <item>The current directory.
264 <item>A compiled in library path which is often <tt>/usr/lib/cc65/lib</tt> on
266 <item>The value of the environment variable <tt/LD65_LIB/ if it is defined.
267 <item>The value of the environment variable <tt/CC65_LIB/ if it is defined.
268 Please note that use of this environment variable is obsolete and may
269 get removed in future versions.
270 <item>Any directory added with the <tt><ref id="option--lib-path"
271 name="--lib-path"></tt> option on the command line.
275 <sect1>Object file search path<p>
277 The object file search path contains in this order:
280 <item>The current directory.
281 <item>A compiled in directory which is often <tt>/usr/lib/cc65/lib</tt> on
283 <item>The value of the environment variable <tt/LD65_OBJ/ if it is defined.
284 <item>The value of the environment variable <tt/CC65_LIB/ if it is defined.
285 Please note that use of this environment variable is obsolete and may
286 get removed in future versions.
287 <item>Any directory added with the <tt><ref id="option--obj-path"
288 name="--obj-path"></tt> option on the command line.
292 <sect1>Config file search path<p>
294 The config file search path contains in this order:
297 <item>The current directory.
298 <item>A compiled in directory which is often <tt>/usr/lib/cc65/lib</tt> on
300 <item>The value of the environment variable <tt/LD65_CFG/ if it is defined.
301 <item>Any directory added with the <tt><ref id="option--cfg-path"
302 name="--cfg-path"></tt> option on the command line.
307 <sect>Detailed workings<p>
309 The linker does several things when combining object modules:
311 First, the command line is parsed from left to right. For each object file
312 encountered (object files are recognized by a magic word in the header, so
313 the linker does not care about the name), imported and exported
314 identifiers are read from the file and inserted in a table. If a library
315 name is given (libraries are also recognized by a magic word, there are no
316 special naming conventions), all modules in the library are checked if an
317 export from this module would satisfy an import from other modules. All
318 modules where this is the case are marked. If duplicate identifiers are
319 found, the linker issues a warning.
321 This procedure (parsing and reading from left to right) does mean, that a
322 library may only satisfy references for object modules (given directly or from
323 a library) named <em/before/ that library. With the command line
326 ld65 crt0.o clib.lib test.o
329 the module test.o may not contain references to modules in the library
330 clib.lib. If this is the case, you have to change the order of the modules
334 ld65 crt0.o test.o clib.lib
337 Step two is, to read the configuration file, and assign start addresses
338 for the segments and define any linker symbols (see <ref id="config-files"
339 name="Configuration files">).
341 After that, the linker is ready to produce an output file. Before doing that,
342 it checks it's data for consistency. That is, it checks for unresolved
343 externals (if the output format is not relocatable) and for symbol type
344 mismatches (for example a zero page symbol is imported by a module as absolute
347 Step four is, to write the actual target files. In this step, the linker will
348 resolve any expressions contained in the segment data. Circular references are
349 also detected in this step (a symbol may have a circular reference that goes
350 unnoticed if the symbol is not used).
352 Step five is to output a map file with a detailed list of all modules,
353 segments and symbols encountered.
355 And, last step, if you give the <tt><ref id="option-v" name="-v"></tt> switch
356 twice, you get a dump of the segment data. However, this may be quite
357 unreadable if you're not a developer:-)
361 <sect>Configuration files<label id="config-files"><p>
363 Configuration files are used to describe the layout of the output file(s). Two
364 major topics are covered in a config file: The memory layout of the target
365 architecture, and the assignment of segments to memory areas. In addition,
366 several other attributes may be specified.
368 Case is ignored for keywords, that is, section or attribute names, but it is
369 <em/not/ ignored for names and strings.
373 <sect1>Memory areas<p>
375 Memory areas are specified in a <tt/MEMORY/ section. Lets have a look at an
376 example (this one describes the usable memory layout of the C64):
380 RAM1: start = $0800, size = $9800;
381 ROM1: start = $A000, size = $2000;
382 RAM2: start = $C000, size = $1000;
383 ROM2: start = $E000, size = $2000;
387 As you can see, there are two ram areas and two rom areas. The names
388 (before the colon) are arbitrary names that must start with a letter, with
389 the remaining characters being letters or digits. The names of the memory
390 areas are used when assigning segments. As mentioned above, case is
391 significant for these names.
393 The syntax above is used in all sections of the config file. The name
394 (<tt/ROM1/ etc.) is said to be an identifier, the remaining tokens up to the
395 semicolon specify attributes for this identifier. You may use the equal sign
396 to assign values to attributes, and you may use a comma to separate
397 attributes, you may also leave both out. But you <em/must/ use a semicolon to
398 mark the end of the attributes for one identifier. The section above may also
399 have looked like this:
402 # Start of memory section
420 There are of course more attributes for a memory section than just start and
421 size. Start and size are mandatory attributes, that means, each memory area
422 defined <em/must/ have these attributes given (the linker will check that). I
423 will cover other attributes later. As you may have noticed, I've used a
424 comment in the example above. Comments start with a hash mark (`#'), the
425 remainder of the line is ignored if this character is found.
430 Let's assume you have written a program for your trusty old C64, and you would
431 like to run it. For testing purposes, it should run in the <tt/RAM/ area. So
432 we will start to assign segments to memory sections in the <tt/SEGMENTS/
437 CODE: load = RAM1, type = ro;
438 RODATA: load = RAM1, type = ro;
439 DATA: load = RAM1, type = rw;
440 BSS: load = RAM1, type = bss, define = yes;
444 What we are doing here is telling the linker, that all segments go into the
445 <tt/RAM1/ memory area in the order specified in the <tt/SEGMENTS/ section. So
446 the linker will first write the <tt/CODE/ segment, then the <tt/RODATA/
447 segment, then the <tt/DATA/ segment - but it will not write the <tt/BSS/
448 segment. Why? Enter the segment type: For each segment specified, you may also
449 specify a segment attribute. There are five possible segment attributes:
453 wprot same as ro but will be marked as write protected in
454 the VICE label file if -Lp is given
456 bss means that this is an uninitialized segment
457 zp a zeropage segment
460 So, because we specified that the segment with the name BSS is of type bss,
461 the linker knows that this is uninitialized data, and will not write it to an
462 output file. This is an important point: For the assembler, the <tt/BSS/
463 segment has no special meaning. You specify, which segments have the bss
464 attribute when linking. This approach is much more flexible than having one
465 fixed bss segment, and is a result of the design decision to supporting an
466 arbitrary segment count.
468 If you specify "<tt/type = bss/" for a segment, the linker will make sure that
469 this segment does only contain uninitialized data (that is, zeroes), and issue
470 a warning if this is not the case.
472 For a <tt/bss/ type segment to be useful, it must be cleared somehow by your
473 program (this happens usually in the startup code - for example the startup
474 code for cc65 generated programs takes care about that). But how does your
475 code know, where the segment starts, and how big it is? The linker is able to
476 give that information, but you must request it. This is, what we're doing with
477 the "<tt/define = yes/" attribute in the <tt/BSS/ definitions. For each
478 segment, where this attribute is true, the linker will export three symbols.
481 __NAME_LOAD__ This is set to the address where the
483 __NAME_RUN__ This is set to the run address of the
484 segment. We will cover run addresses
486 __NAME_SIZE__ This is set to the segment size.
489 Replace <tt/NAME/ by the name of the segment, in the example above, this would
490 be <tt/BSS/. These symbols may be accessed by your code.
492 Now, as we've configured the linker to write the first three segments and
493 create symbols for the last one, there's only one question left: Where does
494 the linker put the data? It would be very convenient to have the data in a
497 <sect1>Output files<p>
499 We don't have any files specified above, and indeed, this is not needed in a
500 simple configuration like the one above. There is an additional attribute
501 "file" that may be specified for a memory area, that gives a file name to
502 write the area data into. If there is no file name given, the linker will
503 assign the default file name. This is "a.out" or the one given with the
504 <tt><ref id="option-o" name="-o"></tt> option on the command line. Since the
505 default behaviour is ok for our purposes, I did not use the attribute in the
506 example above. Let's have a look at it now.
508 The "file" attribute (the keyword may also be written as "FILE" if you like
509 that better) takes a string enclosed in double quotes (`"') that specifies the
510 file, where the data is written. You may specifiy the same file several times,
511 in that case the data for all memory areas having this file name is written
512 into this file, in the order of the memory areas defined in the <tt/MEMORY/
513 section. Let's specify some file names in the <tt/MEMORY/ section used above:
517 RAM1: start = $0800, size = $9800, file = %O;
518 ROM1: start = $A000, size = $2000, file = "rom1.bin";
519 RAM2: start = $C000, size = $1000, file = %O;
520 ROM2: start = $E000, size = $2000, file = "rom2.bin";
524 The <tt/%O/ used here is a way to specify the default behaviour explicitly:
525 <tt/%O/ is replaced by a string (including the quotes) that contains the
526 default output name, that is, "a.out" or the name specified with the <tt><ref
527 id="option-o" name="-o"></tt> option on the command line. Into this file, the
528 linker will first write any segments that go into <tt/RAM1/, and will append
529 then the segments for <tt/RAM2/, because the memory areas are given in this
530 order. So, for the RAM areas, nothing has really changed.
532 We've not used the ROM areas, but we will do that below, so we give the file
533 names here. Segments that go into <tt/ROM1/ will be written to a file named
534 "rom1.bin", and segments that go into <tt/ROM2/ will be written to a file
535 named "rom2.bin". The name given on the command line is ignored in both cases.
538 <sect1>LOAD and RUN addresses (ROMable code)<p>
540 Let us look now at a more complex example. Say, you've successfully tested
541 your new "Super Operating System" (SOS for short) for the C64, and you
542 will now go and replace the ROMs by your own code. When doing that, you
543 face a new problem: If the code runs in RAM, we need not to care about
544 read/write data. But now, if the code is in ROM, we must care about it.
545 Remember the default segments (you may of course specify your own):
549 RODATA read only data
551 BSS uninitialized data, read/write
554 Since <tt/BSS/ is not initialized, we must not care about it now, but what
555 about <tt/DATA/? <tt/DATA/ contains initialized data, that is, data that was
556 explicitly assigned a value. And your program will rely on these values on
557 startup. Since there's no other way to remember the contents of the data
558 segment, than storing it into one of the ROMs, we have to put it there. But
559 unfortunately, ROM is not writeable, so we have to copy it into RAM before
560 running the actual code.
562 The linker cannot help you copying the data from ROM into RAM (this must be
563 done by the startup code of your program), but it has some features that will
564 help you in this process.
566 First, you may not only specify a "<tt/load/" attribute for a segment, but
567 also a "<tt/run/" attribute. The "<tt/load/" attribute is mandatory, and, if
568 you don't specify a "<tt/run/" attribute, the linker assumes that load area
569 and run area are the same. We will use this feature for our data area:
573 CODE: load = ROM1, type = ro;
574 RODATA: load = ROM2, type = ro;
575 DATA: load = ROM2, run = RAM2, type = rw, define = yes;
576 BSS: load = RAM2, type = bss, define = yes;
580 Let's have a closer look at this <tt/SEGMENTS/ section. We specify that the
581 <tt/CODE/ segment goes into <tt/ROM1/ (the one at $A000). The readonly data
582 goes into <tt/ROM2/. Read/write data will be loaded into <tt/ROM2/ but is run
583 in <tt/RAM2/. That means that all references to labels in the <tt/DATA/
584 segment are relocated to be in <tt/RAM2/, but the segment is written to
585 <tt/ROM2/. All your startup code has to do is, to copy the data from it's
586 location in <tt/ROM2/ to the final location in <tt/RAM2/.
588 So, how do you know, where the data is located? This is the second point,
589 where you get help from the linker. Remember the "<tt/define/" attribute?
590 Since we have set this attribute to true, the linker will define three
591 external symbols for the data segment that may be accessed from your code:
594 __DATA_LOAD__ This is set to the address where the segment
595 is loaded, in this case, it is an address in
597 __DATA_RUN__ This is set to the run address of the segment,
598 in this case, it is an address in RAM2.
599 __DATA_SIZE__ This is set to the segment size.
602 So, what your startup code must do, is to copy <tt/__DATA_SIZE__/ bytes from
603 <tt/__DATA_LOAD__/ to <tt/__DATA_RUN__/ before any other routines are called.
604 All references to labels in the <tt/DATA/ segment are relocated to <tt/RAM2/
605 by the linker, so things will work properly.
608 <sect1>Other MEMORY area attributes<p>
610 There are some other attributes not covered above. Before starting the
611 reference section, I will discuss the remaining things here.
613 You may request symbols definitions also for memory areas. This may be
614 useful for things like a software stack, or an i/o area.
618 STACK: start = $C000, size = $1000, define = yes;
622 This will define three external symbols that may be used in your code:
625 __STACK_START__ This is set to the start of the memory
626 area, $C000 in this example.
627 __STACK_SIZE__ The size of the area, here $1000.
628 __STACK_LAST__ This is NOT the same as START+SIZE.
629 Instead, it it defined as the first
630 address that is not used by data. If we
631 don't define any segments for this area,
632 the value will be the same as START.
635 A memory section may also have a type. Valid types are
638 ro for readonly memory
639 rw for read/write memory.
642 The linker will assure, that no segment marked as read/write or bss is put
643 into a memory area that is marked as readonly.
645 Unused memory in a memory area may be filled. Use the "<tt/fill = yes/"
646 attribute to request this. The default value to fill unused space is zero. If
647 you don't like this, you may specify a byte value that is used to fill these
648 areas with the "<tt/fillval/" attribute. This value is also used to fill unfilled
649 areas generated by the assemblers <tt/.ALIGN/ and <tt/.RES/ directives.
652 <sect1>Other SEGMENT attributes<p>
654 Segments may be aligned to some memory boundary. Specify "<tt/align = num/" to
655 request this feature. Num must be a power of two. To align all segments on a
660 CODE: load = ROM1, type = ro, align = $100;
661 RODATA: load = ROM2, type = ro, align = $100;
662 DATA: load = ROM2, run = RAM2, type = rw, define = yes,
664 BSS: load = RAM2, type = bss, define = yes, align = $100;
668 If an alignment is requested, the linker will add enough space to the output
669 file, so that the new segment starts at an address that is divideable by the
670 given number without a remainder. All addresses are adjusted accordingly. To
671 fill the unused space, bytes of zero are used, or, if the memory area has a
672 "<tt/fillval/" attribute, that value. Alignment is always needed, if you have
673 the used the <tt/.ALIGN/ command in the assembler. The alignment of a segment
674 must be equal or greater than the alignment used in the <tt/.ALIGN/ command.
675 The linker will check that, and issue a warning, if the alignment of a segment
676 is lower than the alignment requested in a <tt/.ALIGN/ command of one of the
677 modules making up this segment.
679 For a given segment you may also specify a fixed offset into a memory area or
680 a fixed start address. Use this if you want the code to run at a specific
681 address (a prominent case is the interrupt vector table which must go at
682 address $FFFA). Only one of <tt/ALIGN/ or <tt/OFFSET/ or <tt/START/ may be
683 specified. If the directive creates empty space, it will be filled with zero,
684 of with the value specified with the "<tt/fillval/" attribute if one is given.
685 The linker will warn you if it is not possible to put the code at the
686 specified offset (this may happen if other segments in this area are too
687 large). Here's an example:
691 VECTORS: load = ROM2, type = ro, start = $FFFA;
695 or (for the segment definitions from above)
699 VECTORS: load = ROM2, type = ro, offset = $1FFA;
703 To suppress the warning, the linker issues if it encounters a segment that is
704 not found in any of the input files, use "<tt/optional=yes/" as additional
705 segment attribute. Be careful when using this attribute, because a missing
706 segment may be a sign of a problem, and if you're suppressing the warning,
707 there is no one left to tell you about it.
709 File names may be empty, data from segments assigned to a memory area with
710 an empty file name is discarded. This is useful, if the a memory area has
711 segments assigned that are empty (for example because they are of type
712 bss). In that case, the linker will create an empty output file. This may
713 be suppressed by assigning an empty file name to that memory area.
715 The symbol <tt/%S/ may be used to access the default start address (that is,
716 $200 or the value given on the command line with the <tt><ref id="option-S"
717 name="-S"></tt> option).
721 <sect1>The FILES section<p>
723 The <tt/FILES/ section is used to support other formats than straight binary
724 (which is the default, so binary output files do not need an explicit entry
725 in the <tt/FILES/ section).
727 The <tt/FILES/ section lists output files and as only attribute the format of
728 each output file. Assigning binary format to the default output file would
737 The only other available output format is the o65 format specified by Andre
738 Fachat. It is defined like this:
746 The necessary o65 attributes are defined in a special section labeled
751 <sect1>The FORMAT section<p>
753 The <tt/FORMAT/ section is used to describe file formats. The default (binary)
754 format has currently no attributes, so, while it may be listed in this
755 section, the attribute list is empty. The second supported format, o65, has
756 several attributes that may be defined here.
760 o65: os = lunix, version = 0, type = small,
761 import = LUNIXKERNEL,
772 In addition to the <tt/MEMORY/ and <tt/SEGMENTS/ sections described above, the
773 linker has features that may be enabled by an additional section labeled
774 <tt/FEATURES/. Currently, one such feature is available: <tt/CONDES/ is used
775 to tell the linker to emit module constructor/destructor tables.
779 CONDES: segment = RODATA,
781 label = __CONSTRUCTOR_TABLE__,
782 count = __CONSTRUCTOR_COUNT__;
786 The <tt/CONDES/ feature has several attributes:
790 <tag><tt>segment</tt></tag>
792 This attribute tells the linker into which segment the table should be
793 placed. If the segment does not exist, it is created.
796 <tag><tt>type</tt></tag>
798 Describes the type of the routines to place in the table. Type may be
799 one of the predefined types <tt/constructor/ or <tt/destructor/, or a
800 numeric value between 0 and 6.
803 <tag><tt>label</tt></tag>
805 This specifies the label to use for the table. The label points to the
806 start of the table in memory and may be used from within user written
810 <tag><tt>count</tt></tag>
812 This is an optional attribute. If specified, an additional symbol is
813 defined by the linker using the given name. The value of this symbol
814 is the number of entries (<em/not/ bytes) in the table. While this
815 attribute is optional, it is often useful to define it.
818 <tag><tt>order</tt></tag>
820 Optional attribute that takes one of the keywords <tt/increasing/ or
821 <tt/decreasing/ as an argument. Specifies the sorting order of the entries
822 within the table. The default is <tt/increasing/, which means that the
823 entries are sorted with increasing priority (the first entry has the lowest
824 priority). "Priority" is the priority specified when declaring a symbol as
825 <tt/.CONDES/ with the assembler, higher values mean higher priority. You may
826 change this behaviour by specifying <tt/decreasing/ as the argument, the
827 order of entries is reversed in this case.
829 Please note that the order of entries with equal priority is undefined.
833 Without specifying the <tt/CONDES/ feature, the linker will not create any
834 tables, even if there are <tt/condes/ entries in the object files.
836 For more information see the <tt/.CONDES/ command in the <htmlurl
837 url="ca65.html" name="ca65 manual">.
841 <sect1>Builtin configurations<p>
843 The builtin configurations are part of the linker source. They are also
844 distributed together with the machine specific binary packages (usually in the
845 doc directory) and don't have a special format. So if you need a special
846 configuration, it's a good idea to start with the builtin configuration for
847 your system. In a first step, just replace <tt/-t target/ by <tt/-C
848 configfile/. The go on and modify the config file to suit your needs.
852 <sect>Bugs/Feedback<p>
854 If you have problems using the linker, if you find any bugs, or if you're
855 doing something interesting with it, I would be glad to hear from you. Feel
856 free to contact me by email (<htmlurl url="mailto:uz@cc65.org"
857 name="uz@cc65.org">).
863 ld65 (and all cc65 binutils) are (C) Copyright 1998-2001 Ullrich von
864 Bassewitz. For usage of the binaries and/or sources the following
867 This software is provided 'as-is', without any expressed or implied
868 warranty. In no event will the authors be held liable for any damages
869 arising from the use of this software.
871 Permission is granted to anyone to use this software for any purpose,
872 including commercial applications, and to alter it and redistribute it
873 freely, subject to the following restrictions:
876 <item> The origin of this software must not be misrepresented; you must not
877 claim that you wrote the original software. If you use this software
878 in a product, an acknowledgment in the product documentation would be
879 appreciated but is not required.
880 <item> Altered source versions must be plainly marked as such, and must not
881 be misrepresented as being the original software.
882 <item> This notice may not be removed or altered from any source