-<!doctype linuxdoc system>
+<!doctype linuxdoc system> <!-- -*- text-mode -*- -->
<article>
<title>ld65 Users Guide
-<author>Ullrich von Bassewitz, <htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">
-<date>02.12.2000, 02.10.2001
+<author><url url="mailto:uz@cc65.org" name="Ullrich von Bassewitz">
<abstract>
The ld65 linker combines object files into an executable file. ld65 is highly
<itemize>
-<item> Accept any number of segments to form an executable module.
+<item> Accept any number of segments to form an executable module.
-<item> Resolve arbitrary expressions stored in the object files.
+<item> Resolve arbitrary expressions stored in the object files.
-<item> In case of errors, use the meta information stored in the object files
- to produce helpful error messages. In case of undefined symbols,
- expression range errors, or symbol type mismatches, ld65 is able to
- tell you the exact location in the original assembler source, where
- the symbol was referenced.
+<item> In case of errors, use the meta information stored in the object files
+ to produce helpful error messages. In case of undefined symbols,
+ expression range errors, or symbol type mismatches, ld65 is able to
+ tell you the exact location in the original assembler source, where
+ the symbol was referenced.
-<item> Flexible output. The output of ld65 is highly configurable by a config
- file. More common platforms are supported by builtin configurations
- that may be activated by naming the target system. The output
- generation was designed with different output formats in mind, so
- adding other formats shouldn't be a great problem.
+<item> Flexible output. The output of ld65 is highly configurable by a config
+ file. Some more-common platforms are supported by default configurations
+ that may be activated by naming the target system. The output
+ generation was designed with different output formats in mind, so
+ adding other formats shouldn't be a great problem.
</itemize>
<sect>Usage<p>
-<sect1>Command
line option overview<p>
+<sect1>Command
-line option overview<p>
The linker is called as follows:
---------------------------------------------------------------------------
Usage: ld65 [options] module ...
Short options:
- -C name Use linker config file
- -Ln name Create a VICE label file
- -Lp Mark write protected segments as such (VICE)
- -S addr Set the default start address
- -V Print the linker version
- -h Help (this text)
- -m name Create a map file
- -o name Name the default output file
- -t sys Set the target system
- -v Verbose mode
- -vm Verbose map file
+ -( Start a library group
+ -) End a library group
+ -C name Use linker config file
+ -D sym=val Define a symbol
+ -L path Specify a library search path
+ -Ln name Create a VICE label file
+ -S addr Set the default start address
+ -V Print the linker version
+ -h Help (this text)
+ -m name Create a map file
+ -o name Name the default output file
+ -t sys Set the target system
+ -u sym Force an import of symbol 'sym'
+ -v Verbose mode
+ -vm Verbose map file
Long options:
- --config name Use linker config file
- --help Help (this text)
- --mapfile name Create a map file
- --start-addr addr Set the default start address
- --target sys Set the target system
- --version Print the linker version
+ --allow-multiple-definition Allow multiple definitions
+ --cfg-path path Specify a config file search path
+ --config name Use linker config file
+ --dbgfile name Generate debug information
+ --define sym=val Define a symbol
+ --end-group End a library group
+ --force-import sym Force an import of symbol 'sym'
+ --help Help (this text)
+ --lib file Link this library
+ --lib-path path Specify a library search path
+ --mapfile name Create a map file
+ --module-id id Specify a module id
+ --obj file Link this object file
+ --obj-path path Specify an object file search path
+ --start-addr addr Set the default start address
+ --start-group Start a library group
+ --target sys Set the target system
+ --version Print the linker version
---------------------------------------------------------------------------
</verb></tscreen>
-<sect1>Command
line options in detail<p>
+<sect1>Command
-line options in detail<p>
-Here is a description of all the command line options:
+Here is a description of all of the command-line options:
<descrip>
+ <tag><tt>--allow-multiple-definition</tt></tag>
+
+ Normally when a global symbol is defined multiple times, ld65 will
+ issue an error and not create the output file. This option lets it
+ silently ignore this fact and continue. The first definition of a
+ symbol will be used.
+
+
+ <label id="option--start-group">
+ <tag><tt>-(, --start-group</tt></tag>
+
+ Start a library group. The libraries specified within a group are searched
+ multiple times to resolve crossreferences within the libraries. Normally,
+ crossreferences are resolved only within a library, that is the library is
+ searched multiple times. Libraries specified later on the command line
+ cannot reference otherwise unreferenced symbols in libraries specified
+ earlier, because the linker has already handled them. Library groups are
+ a solution for this problem, because the linker will search repeatedly
+ through all libraries specified in the group, until all possible open
+ symbol references have been satisfied.
+
+
+ <tag><tt>-), --end-group</tt></tag>
+
+ End a library group. See the explanation of the <tt><ref
+ id="option--start-group" name="--start-group"></tt> option.
+
+
<tag><tt>-h, --help</tt></tag>
Print the short option summary shown above.
<tag><tt>-o name</tt></tag>
The -o switch is used to give the name of the default output file.
- Depending on your output configuration, this name may NOT be used as
- name for the output file. However, for the builtin configurations, this
+ Depending on your output configuration, this name <em/might not/ be used as the
+ name for the output file. However, for the default configurations, this
name is used for the output file name.
<tag><tt>-t sys, --target sys</tt></tag>
The argument for the -t switch is the name of the target system. Since this
- switch will activate a builtin configuration, it may not be used together
+ switch will activate a default configuration, it may not be used together
with the <tt><ref id="option-C" name="-C"></tt> option. The following target
systems are currently supported:
<itemize>
<item>none
+ <item>module
<item>apple2
+ <item>apple2enh
+ <item>atari2600
<item>atari
+ <item>atarixl
<item>atmos
<item>c16 (works also for the c116 with memory up to 32K)
<item>c64
<item>c128
- <item>plus4
- <item>cbm510 (CBM-II series with 40 column video)
- <item>cbm610 (all CBM series-II computers with 80 column video)
+ <item>cbm510 (CBM-II series with 40-column video)
+ <item>cbm610 (all CBM series-II computers with 80-column video)
+ <item>geos-apple
+ <item>geos-cbm
+ <item>lunix
+ <item>lynx
+ <item>nes
<item>pet (all CBM PET systems except the 2001)
- <item>geos
+ <item>plus4
+ <item>sim6502
+ <item>sim65c02
+ <item>supervision
+ <item>telestrat
+ <item>vic20
</itemize>
There are a few more targets defined but neither of them is actually
- supported. See <ref id="builtin-configs" name="builtin configurations"> for
- more information.
+ supported.
+
+
+ <tag><tt>-u sym[:addrsize], --force-import sym[:addrsize]</tt></tag>
+
+ Force an import of a symbol. While object files are always linked to the
+ output file, regardless if there are any references, object modules from
+ libraries get only linked in if an import can be satisfied by this module.
+ The <tt/--force-import/ option may be used to add a reference to a symbol and
+ as a result force linkage of the module that exports the identifier.
+
+ The name of the symbol may optionally be followed by a colon and an address-size
+ specifier. If no address size is specified, the default address size
+ for the target machine is used.
+
+ Please note that the symbol name needs to have the internal representation,
+ meaning you have to prepend an underscore for C identifiers.
<label id="option-v">
Must be used in conjunction with <tt><ref id="option-m" name="-m"></tt>
(generate map file). Normally the map file will not include empty segments
and sections, or unreferenced symbols. Using this option, you can force the
- linker to include all this information into the map file.
+ linker to include all that information into the map file. Also, it will
+ include a second <tt/Exports/ list. The first list is sorted by name;
+ the second one is sorted by value.
<label id="option-C">
id="option-t" name="-t"></tt>.
- <tag><tt>-Ln</tt></tag>
+ <label id="option-D">
+ <tag><tt>-D sym=value, --define sym=value</tt></tag>
- This option allows you to create a file that contains all global labels and
- may be loaded into VICE emulator using the <tt/ll/ (load label) command. You
- may use this to debug your code with VICE. Note: Older versions had some
- bugs in the label code. If you have problems, please get the latest VICE
- version.
+ This option allows to define an external symbol on the command line. Value
+ may start with a '$' sign or with <tt/0x/ for hexadecimal values,
+ otherwise a leading zero denotes octal values. See also <ref
+ id="SYMBOLS" name="the SYMBOLS section"> in the configuration file.
- <tag><tt>-Lp</tt></tag>
+ <label id="option--lib-path">
+ <tag><tt>-L path, --lib-path path</tt></tag>
- Deprecated option.
+ Specify a library search path. This option may be used more than once. It
+ adds a directory to the search path for library files. Libraries specified
+ without a path are searched in the current directory, in the list of
+ directories specified using <tt/--lib-path/, in directories given by
+ environment variables, and in a built-in default directory.
+
+
+ <tag><tt>-Ln</tt></tag>
+
+ This option allows you to create a file that contains all global labels and
+ may be loaded into the VICE emulator using the <tt/ll/ (load label) command
+ or into the Oricutron emulator using the <tt/sl/ (symbols load) command. You
+ may use this to debug your code with VICE. Note: Older versions had some
+ bugs in the label code. If you have problems, please get the latest <url
+ url="http://vice-emu.sourceforge.net" name="VICE"> version.
<label id="option-S">
<tag><tt>-S addr, --start-addr addr</tt></tag>
Using -S you may define the default starting address. If and how this
- address is used depends on the config file in use. For the builtin
- configurations, only the "none" system honors an explicit start address,
- all other builtin config provide their own.
+ address is used depends on the config file in use. For the default
+ configurations, only the "none", "apple2" and "apple2enh" systems honor an
+ explicit start address, all other default configs provide their own.
<tag><tt>-V, --version</tt></tag>
- This option print the version number of the linker. If you send any
+ This option prints the version number of the linker. If you send any
suggestions or bugfixes, please include this number.
+
+ <label id="option--cfg-path">
+ <tag><tt>--cfg-path path</tt></tag>
+
+ Specify a config file search path. This option may be used more than once.
+ It adds a directory to the search path for config files. A config file given
+ with the <tt><ref id="option-C" name="-C"></tt> option that has no path in
+ its name is searched in the current directory, in the list of directories
+ specified using <tt/--cfg-path/, in directories given by environment variables,
+ and in a built-in default directory.
+
+
+ <label id="option--dbgfile">
+ <tag><tt>--dbgfile name</tt></tag>
+
+ Specify an output file for debug information. Available information will be
+ written to this file. Using the <tt/-g/ option for the compiler and assembler
+ will increase the amount of information available. Please note that debug
+ information generation is currently being developed, so the format of the
+ file and its contents are subject to change without further notice.
+
+
+ <tag><tt>--lib file</tt></tag>
+
+ Links a library to the output. Use this command-line option instead of just
+ naming the library file, if the linker is not able to determine the file
+ type because of an unusual extension.
+
+
+ <tag><tt>--obj file</tt></tag>
+
+ Links an object file to the output. Use this command-line option instead
+ of just naming the object file, if the linker is not able to determine the
+ file type because of an unusual extension.
+
+
+ <label id="option--obj-path">
+ <tag><tt>--obj-path path</tt></tag>
+
+ Specify an object file search path. This option may be used more than once.
+ It adds a directory to the search path for object files. An object file
+ passed to the linker that has no path in its name is searched in the current
+ directory, in the list of directories specified using <tt/--obj-path/, in
+ directories given by environment variables, and in a built-in default directory.
+
</descrip>
-If one of the modules is not found in the current directory, and the module
-name does not have a path component, the value of the environment variable
-<tt/CC65_LIB/ is prepended to the name, and the linker tries to open the
-module with this new name.
+
+
+<sect>Search paths<p>
+
+Starting with version 2.10, there are now several search-path lists for files needed
+by the linker: one for libraries, one for object files, and one for config
+files.
+
+
+<sect1>Library search path<p>
+
+The library search-path list contains in this order:
+
+<enum>
+<item>The current directory.
+<item>Any directory added with the <tt><ref id="option--lib-path"
+ name="--lib-path"></tt> option on the command line.
+<item>The value of the environment variable <tt/LD65_LIB/ if it is defined.
+<item>A subdirectory named <tt/lib/ of the directory defined in the environment
+ variable <tt/CC65_HOME/, if it is defined.
+<item>An optionally compiled-in library path.
+</enum>
+
+
+<sect1>Object file search path<p>
+
+The object file search-path list contains in this order:
+
+<enum>
+<item>The current directory.
+<item>Any directory added with the <tt><ref id="option--obj-path"
+ name="--obj-path"></tt> option on the command line.
+<item>The value of the environment variable <tt/LD65_OBJ/ if it is defined.
+<item>A subdirectory named <tt/obj/ of the directory defined in the environment
+ variable <tt/CC65_HOME/, if it is defined.
+<item>An optionally compiled-in directory.
+</enum>
+
+
+<sect1>Config file search path<p>
+
+The config file search-path list contains in this order:
+
+<enum>
+<item>The current directory.
+<item>Any directory added with the <tt><ref id="option--cfg-path"
+ name="--cfg-path"></tt> option on the command line.
+<item>The value of the environment variable <tt/LD65_CFG/ if it is defined.
+<item>A subdirectory named <tt/cfg/ of the directory defined in the environment
+ variable <tt/CC65_HOME/, if it is defined.
+<item>An optionally compiled-in directory.
+</enum>
special naming conventions), all modules in the library are checked if an
export from this module would satisfy an import from other modules. All
modules where this is the case are marked. If duplicate identifiers are
-found, the linker issues a warning.
+found, the linker issues warnings.
-This procedure (parsing and reading from left to right) does mean, that a
+That procedure (parsing and reading from left to right) does mean that a
library may only satisfy references for object modules (given directly or from
a library) named <em/before/ that library. With the command line
<tscreen><verb>
- ld65 crt0.o clib.lib test.o
+ ld65 crt0.o clib.lib test.o
</verb></tscreen>
-the module test.o may not contain references to modules in the library
-clib.lib. If this is the case, you have to change the order of the modules
+the module <tt/test.o/ must not contain references to modules in the library
+<tt/clib.lib/. But, if it does, you have to change the order of the modules
on the command line:
<tscreen><verb>
- ld65 crt0.o test.o clib.lib
+ ld65 crt0.o test.o clib.lib
</verb></tscreen>
Step two is, to read the configuration file, and assign start addresses
name="Configuration files">).
After that, the linker is ready to produce an output file. Before doing that,
-it checks it's data for consistency. That is, it checks for unresolved
+it checks its data for consistency. That is, it checks for unresolved
externals (if the output format is not relocatable) and for symbol type
-mismatches (for example a zero page symbol is imported by a module as absolute
+mismatches (for example a zero-page symbol is imported by a module as an absolute
symbol).
Step four is, to write the actual target files. In this step, the linker will
And, last step, if you give the <tt><ref id="option-v" name="-v"></tt> switch
twice, you get a dump of the segment data. However, this may be quite
-unreadable if you're not a developer:-)
+unreadable if you're not a developer. :-)
<sect1>Memory areas<p>
-Memory areas are specified in a <tt/MEMORY/ section. Lets have a look at an
+Memory areas are specified in a <tt/MEMORY/ section. Let's have a look at an
example (this one describes the usable memory layout of the C64):
<tscreen><verb>
- MEMORY {
- RAM1: start = $0800, size = $9800;
- ROM1: start = $A000, size = $2000;
- RAM2: start = $C000, size = $1000;
- ROM2: start = $E000, size = $2000;
- }
+ MEMORY {
+ RAM1: start = $0800, size = $9800;
+ ROM1: start = $A000, size = $2000;
+ RAM2: start = $C000, size = $1000;
+ ROM2: start = $E000, size = $2000;
+ }
</verb></tscreen>
-As you can see, there are two ram areas and two rom areas. The names
+As you can see, there are two RAM areas and two ROM areas. The names
(before the colon) are arbitrary names that must start with a letter, with
the remaining characters being letters or digits. The names of the memory
areas are used when assigning segments. As mentioned above, case is
-significant for these names.
+significant for those names.
The syntax above is used in all sections of the config file. The name
(<tt/ROM1/ etc.) is said to be an identifier, the remaining tokens up to the
have looked like this:
<tscreen><verb>
- # Start of memory section
- MEMORY
- {
- RAM1:
- start $0800
- size $9800;
- ROM1:
- start $A000
- size $2000;
- RAM2:
- start $C000
- size $1000;
- ROM2:
- start $E000
- size $2000;
- }
+ # Start of memory section
+ MEMORY
+ {
+ RAM1:
+ start $0800
+ size $9800;
+ ROM1:
+ start $A000
+ size $2000;
+ RAM2:
+ start $C000
+ size $1000;
+ ROM2:
+ start $E000
+ size $2000;
+ }
</verb></tscreen>
There are of course more attributes for a memory section than just start and
size. Start and size are mandatory attributes, that means, each memory area
defined <em/must/ have these attributes given (the linker will check that). I
will cover other attributes later. As you may have noticed, I've used a
-comment in the example above. Comments start with a hash mark (`#'), the
+comment in the example above. Comments start with a hash mark ('#'), the
remainder of the line is ignored if this character is found.
section:
<tscreen><verb>
- SEGMENTS {
- CODE: load = RAM1, type = ro;
- RODATA: load = RAM1, type = ro;
- DATA: load = RAM1, type = rw;
- BSS: load = RAM1, type = bss, define = yes;
- }
+ SEGMENTS {
+ CODE: load = RAM1, type = ro;
+ RODATA: load = RAM1, type = ro;
+ DATA: load = RAM1, type = rw;
+ BSS: load = RAM1, type = bss, define = yes;
+ }
</verb></tscreen>
What we are doing here is telling the linker, that all segments go into the
<tt/RAM1/ memory area in the order specified in the <tt/SEGMENTS/ section. So
the linker will first write the <tt/CODE/ segment, then the <tt/RODATA/
segment, then the <tt/DATA/ segment - but it will not write the <tt/BSS/
-segment. Why? Enter the segment type: For each segment specified, you may also
+segment. Why? Here enters the segment type: For each segment specified, you may also
specify a segment attribute. There are five possible segment attributes:
<tscreen><verb>
- ro means readonly
- wprot same as ro but will be marked as write protected in
- the VICE label file if -Lp is given
- rw means read/write
- bss means that this is an uninitialized segment
- zp a zeropage segment
+ ro means readonly
+ rw means read/write
+ bss means that this is an uninitialized segment
+ zp a zeropage segment
+ overwrite a segment that overwrites (parts of) another one
+
</verb></tscreen>
So, because we specified that the segment with the name BSS is of type bss,
For a <tt/bss/ type segment to be useful, it must be cleared somehow by your
program (this happens usually in the startup code - for example the startup
-code for cc65 generated programs takes care about that). But how does your
+code for cc65-generated programs takes care about that). But how does your
code know, where the segment starts, and how big it is? The linker is able to
give that information, but you must request it. This is, what we're doing with
the "<tt/define = yes/" attribute in the <tt/BSS/ definitions. For each
segment, where this attribute is true, the linker will export three symbols.
<tscreen><verb>
- __NAME_LOAD__ This is set to the address where the
- segment is loaded.
- __NAME_RUN__ This is set to the run address of the
- segment. We will cover run addresses
- later.
- __NAME_SIZE__ This is set to the segment size.
+ __NAME_LOAD__ This is set to the address where the
+ segment is loaded.
+ __NAME_RUN__ This is set to the run address of the
+ segment. We will cover run addresses
+ later.
+ __NAME_SIZE__ This is set to the segment size.
</verb></tscreen>
Replace <tt/NAME/ by the name of the segment, in the example above, this would
write the area data into. If there is no file name given, the linker will
assign the default file name. This is "a.out" or the one given with the
<tt><ref id="option-o" name="-o"></tt> option on the command line. Since the
-default behaviour is ok for our purposes, I did not use the attribute in the
+default behaviour is OK for our purposes, I did not use the attribute in the
example above. Let's have a look at it now.
The "file" attribute (the keyword may also be written as "FILE" if you like
-that better) takes a string enclosed in double quotes (`"') that specifies the
-file, where the data is written. You may specifiy the same file several times,
+that better) takes a string enclosed in double quotes ('&dquot;') that specifies the
+file, where the data is written. You may specify the same file several times,
in that case the data for all memory areas having this file name is written
into this file, in the order of the memory areas defined in the <tt/MEMORY/
section. Let's specify some file names in the <tt/MEMORY/ section used above:
<tscreen><verb>
- MEMORY {
- RAM1: start = $0800, size = $9800, file = %O;
- ROM1: start = $A000, size = $2000, file = "rom1.bin";
- RAM2: start = $C000, size = $1000, file = %O;
- ROM2: start = $E000, size = $2000, file = "rom2.bin";
- }
+ MEMORY {
+ RAM1: start = $0800, size = $9800, file = %O;
+ ROM1: start = $A000, size = $2000, file = "rom1.bin";
+ RAM2: start = $C000, size = $1000, file = %O;
+ ROM2: start = $E000, size = $2000, file = "rom2.bin";
+ }
</verb></tscreen>
The <tt/%O/ used here is a way to specify the default behaviour explicitly:
"rom1.bin", and segments that go into <tt/ROM2/ will be written to a file
named "rom2.bin". The name given on the command line is ignored in both cases.
+Assigning an empty file name for a memory area will discard the data written
+to it. This is useful, if the memory area has segments assigned that are empty
+(for example because they are of type bss). In that case, the linker will
+create an empty output file. This may be suppressed by assigning an empty file
+name to that memory area.
+
+The <tt/%O/ sequence is also allowed inside a string. So using
+
+<tscreen><verb>
+ MEMORY {
+ ROM1: start = $A000, size = $2000, file = "%O-1.bin";
+ ROM2: start = $E000, size = $2000, file = "%O-2.bin";
+ }
+</verb></tscreen>
+
+would write two files that start with the name of the output file specified on
+the command line, with "-1.bin" and "-2.bin" appended respectively. Because
+'%' is used as an escape char, the sequence "%%" has to be used if a single
+percent sign is required.
+
+<sect1>OVERWRITE segments<p>
+
+There are situations when you may wish to overwrite some part (or parts) of a
+segment with another one. Perhaps you are modifying an OS ROM that has its
+public subroutines at fixed, well-known addresses, and you want to prevent them
+from shifting to other locations in memory if your changed code takes less
+space. Or you are updating a block of code available in binary-only form with
+fixes that are scattered in various places. Generally, whenever you want to
+minimize disturbance to an existing code brought on by your updates, OVERWRITE
+segments are worth considering.
+
+Here is an example:
+
+<tscreen><verb>
+MEMORY {
+ RAM: file = "", start = $6000, size = $2000, type=rw;
+ ROM: file = %O, start = $8000, size = $8000, type=ro;
+}
+</verb></tscreen>
+
+Nothing unusual so far, just two memory blocks - one RAM, one ROM. Now let's
+look at the segment configuration:
+
+<tscreen><verb>
+SEGMENTS {
+ RAM: load = RAM, type = bss;
+ ORIGINAL: load = ROM, type = ro;
+ FASTCOPY: load = ROM, start=$9000, type = overwrite;
+ JMPPATCH1: load = ROM, start=$f7e8, type = overwrite;
+ DEBUG: load = ROM, start=$8000, type = overwrite;
+ VERSION: load = ROM, start=$e5b7, type = overwrite;
+}
+</verb></tscreen>
+
+Segment named ORIGINAL contains the original code, disassembled or provided in
+a binary form (i.e. using <tt/.INCBIN/ directive; see the <tt/ca65/ assembler
+document). Subsequent four segments will be relocated to addresses specified
+by their "start" attributes ("offset" can also be used) and then will overwrite
+whatever was at these locations in the ORIGINAL segment. In the end, resulting
+binary output file will thus contain original data with the exception of four
+sequences starting at $9000, $f7e8, $8000 and $e5b7, which will sport code from
+their respective segments. How long these sequences will be depends on the
+lengths of corresponding segments - they can even overlap, so think what you're
+doing.
+
+Finally, note that OVERWRITE segments should be the final segments loaded to a
+particular memory area, and that they need at least one of "start" or "offset"
+attributes specified.
<sect1>LOAD and RUN addresses (ROMable code)<p>
Remember the default segments (you may of course specify your own):
<tscreen><verb>
- CODE read only code
- RODATA read only data
- DATA read/write data
- BSS uninitialized data, read/write
+ CODE read-only code
+ RODATA read-only data
+ DATA read/write data
+ BSS uninitialized data, read/write
</verb></tscreen>
Since <tt/BSS/ is not initialized, we must not care about it now, but what
about <tt/DATA/? <tt/DATA/ contains initialized data, that is, data that was
explicitly assigned a value. And your program will rely on these values on
-startup. Since there's no other way to remember the contents of the data
-segment, than storing it into one of the ROMs, we have to put it there. But
-unfortunately, ROM is not writeable, so we have to copy it into RAM before
+startup. Since there's no way to remember the contents of the data segment,
+other than storing it into one of the ROMs, we have to put it there. But
+unfortunately, ROM is not writable, so we have to copy it into RAM before
running the actual code.
-The linker cannot help you copying the data from ROM into RAM (this must be
-done by the startup code of your program), but it has some features that will
-help you in this process.
+The linker won't copy the data from ROM into RAM for you (this must be done by
+the startup code of your program), but it has some features that will help you
+in this process.
First, you may not only specify a "<tt/load/" attribute for a segment, but
also a "<tt/run/" attribute. The "<tt/load/" attribute is mandatory, and, if
and run area are the same. We will use this feature for our data area:
<tscreen><verb>
- SEGMENTS {
- CODE: load = ROM1, type = ro;
- RODATA: load = ROM2, type = ro;
- DATA: load = ROM2, run = RAM2, type = rw, define = yes;
- BSS: load = RAM2, type = bss, define = yes;
- }
+ SEGMENTS {
+ CODE: load = ROM1, type = ro;
+ RODATA: load = ROM2, type = ro;
+ DATA: load = ROM2, run = RAM2, type = rw, define = yes;
+ BSS: load = RAM2, type = bss, define = yes;
+ }
</verb></tscreen>
Let's have a closer look at this <tt/SEGMENTS/ section. We specify that the
goes into <tt/ROM2/. Read/write data will be loaded into <tt/ROM2/ but is run
in <tt/RAM2/. That means that all references to labels in the <tt/DATA/
segment are relocated to be in <tt/RAM2/, but the segment is written to
-<tt/ROM2/. All your startup code has to do is, to copy the data from it's
+<tt/ROM2/. All your startup code has to do is, to copy the data from its
location in <tt/ROM2/ to the final location in <tt/RAM2/.
So, how do you know, where the data is located? This is the second point,
external symbols for the data segment that may be accessed from your code:
<tscreen><verb>
- __DATA_LOAD__ This is set to the address where the segment
- is loaded, in this case, it is an address in
- ROM2.
- __DATA_RUN__ This is set to the run address of the segment,
- in this case, it is an address in RAM2.
- __DATA_SIZE__ This is set to the segment size.
+ __DATA_LOAD__ This is set to the address where the segment
+ is loaded, in this case, it is an address in
+ ROM2.
+ __DATA_RUN__ This is set to the run address of the segment,
+ in this case, it is an address in RAM2.
+ __DATA_SIZE__ This is set to the segment size.
</verb></tscreen>
So, what your startup code must do, is to copy <tt/__DATA_SIZE__/ bytes from
All references to labels in the <tt/DATA/ segment are relocated to <tt/RAM2/
by the linker, so things will work properly.
+There's a library subroutine called <tt/copydata/ (in a module named
+<tt/copydata.s/) that might be used to do actual copying. Be sure to have a
+look at it's inner workings before using it!
+
<sect1>Other MEMORY area attributes<p>
reference section, I will discuss the remaining things here.
You may request symbols definitions also for memory areas. This may be
-useful for things like a software stack, or an i/o area.
+useful for things like a software stack, or an I/O area.
<tscreen><verb>
- MEMORY {
- STACK: start = $C000, size = $1000, define = yes;
- }
+ MEMORY {
+ STACK: start = $C000, size = $1000, define = yes;
+ }
</verb></tscreen>
-This will define three external symbols that may be used in your code:
+This will define some external symbols that may be used in your code:
<tscreen><verb>
- __STACK_START__ This is set to the start of the memory
- area, $C000 in this example.
- __STACK_SIZE__ The size of the area, here $1000.
- __STACK_LAST__ This is NOT the same as START+SIZE.
- Instead, it it defined as the first
- address that is not used by data. If we
- don't define any segments for this area,
- the value will be the same as START.
+ __STACK_START__ This is set to the start of the memory
+ area, $C000 in this example.
+ __STACK_SIZE__ The size of the area, here $1000.
+ __STACK_LAST__ This is NOT the same as START+SIZE.
+ Instead, it is defined as the first
+ address that is not used by data. If we
+ don't define any segments for this area,
+ the value will be the same as START.
+ __STACK_FILEOFFS__ The binary offset in the output file. This
+ is not defined for relocatable output file
+ formats (o65).
</verb></tscreen>
A memory section may also have a type. Valid types are
<tscreen><verb>
- ro for readonly memory
- rw for read/write memory.
+ ro for readonly memory
+ rw for read/write memory.
</verb></tscreen>
The linker will assure, that no segment marked as read/write or bss is put
Unused memory in a memory area may be filled. Use the "<tt/fill = yes/"
attribute to request this. The default value to fill unused space is zero. If
you don't like this, you may specify a byte value that is used to fill these
-areas with the "<tt/fillval/" attribute. This value is also used to fill unfilled
-areas generated by the assemblers <tt/.ALIGN/ and <tt/.RES/ directives.
+areas with the "<tt/fillval/" attribute. If there is no "<tt/fillval/"
+attribute for the segment, the "<tt/fillval/" attribute of the memory area (or
+its default) is used instead. This means that the value may also be used to
+fill unfilled areas generated by the assembler's <tt/.ALIGN/ and <tt/.RES/
+directives.
+
+The symbol <tt/%S/ may be used to access the default start address (that is,
+the one defined in <ref id="FEATURES" name="the FEATURES section">, or the
+value given on the command line with the <tt><ref id="option-S" name="-S"></tt>
+option).
+
+To support systems with banked memory, a special attribute named <tt/bank/ is
+available. The attribute value is an arbitrary 32-bit integer. The assembler
+has a builtin function named <tt/.BANK/ which may be used with an argument
+that has a segment reference (for example a symbol). The result of this
+function is the value of the bank attribute for the run memory area of the
+segment.
<sect1>Other SEGMENT attributes<p>
Segments may be aligned to some memory boundary. Specify "<tt/align = num/" to
-request this feature. Num must be a power of two. To align all segments on a
-page boundary, use
+request this feature. To align all segments on a page boundary, use
<tscreen><verb>
- SEGMENTS {
- CODE: load = ROM1, type = ro, align = $100;
- RODATA: load = ROM2, type = ro, align = $100;
- DATA: load = ROM2, run = RAM2, type = rw, define = yes,
- align = $100;
- BSS: load = RAM2, type = bss, define = yes, align = $100;
- }
+ SEGMENTS {
+ CODE: load = ROM1, type = ro, align = $100;
+ RODATA: load = ROM2, type = ro, align = $100;
+ DATA: load = ROM2, run = RAM2, type = rw, define = yes,
+ align = $100;
+ BSS: load = RAM2, type = bss, define = yes, align = $100;
+ }
</verb></tscreen>
If an alignment is requested, the linker will add enough space to the output
-file, so that the new segment starts at an address that is divideable by the
+file, so that the new segment starts at an address that is dividable by the
given number without a remainder. All addresses are adjusted accordingly. To
fill the unused space, bytes of zero are used, or, if the memory area has a
"<tt/fillval/" attribute, that value. Alignment is always needed, if you have
-the used the <tt/.ALIGN/ command in the assembler. The alignment of a segment
+used the <tt/.ALIGN/ command in the assembler. The alignment of a segment
must be equal or greater than the alignment used in the <tt/.ALIGN/ command.
The linker will check that, and issue a warning, if the alignment of a segment
-is lower than the alignment requested in a <tt/.ALIGN/ command of one of the
+is lower than the alignment requested in an <tt/.ALIGN/ command of one of the
modules making up this segment.
For a given segment you may also specify a fixed offset into a memory area or
large). Here's an example:
<tscreen><verb>
- SEGMENTS {
- VECTORS: load = ROM2, type = ro, start = $FFFA;
- }
+ SEGMENTS {
+ VECTORS: load = ROM2, type = ro, start = $FFFA;
+ }
</verb></tscreen>
or (for the segment definitions from above)
<tscreen><verb>
- SEGMENTS {
- VECTORS: load = ROM2, type = ro, offset = $1FFA;
- }
+ SEGMENTS {
+ VECTORS: load = ROM2, type = ro, offset = $1FFA;
+ }
</verb></tscreen>
-File names may be empty, data from segments assigned to a memory area with
-an empty file name is discarded. This is useful, if the a memory area has
-segments assigned that are empty (for example because they are of type
-bss). In that case, the linker will create an empty output file. This may
-be suppressed by assigning an empty file name to that memory area.
-
-The symbol <tt/%S/ may be used to access the default start address (that is,
-$200 or the value given on the command line with the <tt><ref id="option-S"
-name="-S"></tt> option).
-
-
+The "<tt/align/", "<tt/start/" and "<tt/offset/" attributes change placement
+of the segment in the run memory area, because this is what is usually
+desired. If load and run memory areas are equal (which is the case if only the
+load memory area has been specified), the attributes will also work. There is
+also an "<tt/align_load/" attribute that may be used to align the start of the
+segment in the load memory area, in case different load and run areas have
+been specified. There are no special attributes to set start or offset for
+just the load memory area.
+
+A "<tt/fillval/" attribute may not only be specified for a memory area, but
+also for a segment. The value must be an integer between 0 and 255. It is used
+as the fill value for space reserved by the assembler's <tt/.ALIGN/ and <tt/.RES/
+commands. It is also used as the fill value for space between sections (part of a
+segment that comes from one object file) caused by alignment, but not for
+space that preceeds the first section.
+
+To suppress the warning, the linker issues if it encounters a segment that is
+not found in any of the input files, use "<tt/optional=yes/" as an additional
+segment attribute. Be careful when using this attribute, because a missing
+segment may be a sign of a problem, and if you're suppressing the warning,
+there is no one left to tell you about it.
<sect1>The FILES section<p>
look like this:
<tscreen><verb>
- FILES {
- %O: format = bin;
- }
+ FILES {
+ %O: format = bin;
+ }
</verb></tscreen>
-The only other available output format is the o65 format specified by Andre
-Fachat. It is defined like this:
+There are two other available formats, one is the o65 format specified by Andre
+Fachat (see the <url url="http://www.6502.org/users/andre/o65/fileformat.html"
+name="6502 binary relocation format specification">). It is defined like this:
<tscreen><verb>
- FILES {
- %O: format = o65;
- }
+ FILES {
+ %O: format = o65;
+ }
</verb></tscreen>
-The necessary o65 attributes are defined in a special section labeled
-<tt/FORMAT/.
+The other format available is the Atari (xex) segmented file format, this is
+the standard format used by Atari DOS 2.0 and upward file managers in the Atari
+8-bit computers, and it is defined like this:
+<tscreen><verb>
+ FILES {
+ %O: format = atari;
+ }
+</verb></tscreen>
+In the Atari segmented file format, the linker will write each <tt/MEMORY/ area
+as a new segment, including a header with the start and end address.
-<sect1>The FORMAT section<p>
+The necessary o65 or Atari attributes are defined in a special section labeled
+<ref id="FORMAT" name="FORMAT">.
+
+
+
+<sect1>The FORMAT section<label id="FORMAT"><p>
The <tt/FORMAT/ section is used to describe file formats. The default (binary)
format has currently no attributes, so, while it may be listed in this
-section, the attribute list is empty. The second supported format, o65, has
-several attributes that may be defined here.
+section, the attribute list is empty. The second supported format,
+<url url="http://www.6502.org/users/andre/o65/fileformat.html" name="o65">,
+has several attributes that may be defined here.
<tscreen><verb>
FORMATS {
}
</verb></tscreen>
+The Atari file format has two attributes:
+
+<descrip>
+
+ <tag><tt>RUNAD = symbol</tt></tag>
+ Specify a symbol as the run address of the binary, the loader will call this
+ address after all the file is loaded in memory. If the attribute is omitted,
+ no run address is included in the file.
+ <tag><tt>INITAD = memory_area : symbol</tt></tag>
+ Specify a symbol as the initialization address for the given memory area.
+ The binary loader will call this address just after the memory area is loaded
+ into memory, before continuing loading the rest of the file.
+
+</descrip>
-<sect1>Features<p>
+
+<tscreen><verb>
+ FORMATS {
+ atari: runad = _start;
+ }
+</verb></tscreen>
+
+
+<sect1>The FEATURES section<label id="FEATURES"><p>
In addition to the <tt/MEMORY/ and <tt/SEGMENTS/ sections described above, the
linker has features that may be enabled by an additional section labeled
-<tt/FEATURES/. Currently, one such feature is available: <tt/CONDES/ is used
-to tell the linker to emit module constructor/destructor tables.
+<tt/FEATURES/.
+
+
+<sect2>The CONDES feature<p>
+
+<tt/CONDES/ is used to tell the linker to emit module constructor/destructor
+tables.
<tscreen><verb>
- FEATURES {
- CONDES: segment = RODATA,
- type = constructor,
- label = __CONSTRUCTOR_TABLE__,
- count = __CONSTRUCTOR_COUNT__;
- }
+ FEATURES {
+ CONDES: segment = RODATA,
+ type = constructor,
+ label = __CONSTRUCTOR_TABLE__,
+ count = __CONSTRUCTOR_COUNT__;
+ }
</verb></tscreen>
The <tt/CONDES/ feature has several attributes:
<tag><tt>type</tt></tag>
- Describes the type of the routines to place in the table. Type may be
- one of the predefined types <tt/constructor/ or <tt/destructor/, or a
- numeric value between 0 and 6.
+ Describes the type of the routines to place in the table. Type may be one of
+ the predefined types <tt/constructor/, <tt/destructor/, <tt/interruptor/, or
+ a numeric value between 0 and 6.
<tag><tt>label</tt></tag>
- This specifies the label to use for the table. The label points to the
- start of the table in memory and may be used from within user written
- code.
+ This specifies the label to use for the table. The label points to the start
+ of the table in memory and may be used from within user-written code.
<tag><tt>count</tt></tag>
- This is an optional attribute. If specified, an additional symbol is
- defined by the linker using the given name. The value of this symbol
- is the number of entries (<em/not/ bytes) in the table. While this
- attribute is optional, it is often useful to define it.
+ This is an optional attribute. If specified, an additional symbol is defined
+ by the linker using the given name. The value of this symbol is the number
+ of entries (<em/not/ bytes) in the table. While this attribute is optional,
+ it is often useful to define it.
<tag><tt>order</tt></tag>
- Optional attribute that takes one of the keywords <tt/increasing/ or
+ An optional attribute that takes one of the keywords <tt/increasing/ or
<tt/decreasing/ as an argument. Specifies the sorting order of the entries
within the table. The default is <tt/increasing/, which means that the
entries are sorted with increasing priority (the first entry has the lowest
- priority). You may change this behaviour by specifying <tt/decreasing/ as
- the argument, the order of entries is reversed in this case.
+ priority). "Priority" is the priority specified when declaring a symbol as
+ <tt/.CONDES/ with the assembler, higher values mean higher priority. You may
+ change this behaviour by specifying <tt/decreasing/ as the argument, the
+ order of entries is reversed in this case.
Please note that the order of entries with equal priority is undefined.
+ <tag><tt>import</tt></tag>
+
+ This attribute defines a valid symbol name, that is added as an import
+ to the modules defining a constructor/destructor of the given type.
+ This can be used to force linkage of a module if this module exports the
+ requested symbol.
+
</descrip>
Without specifying the <tt/CONDES/ feature, the linker will not create any
tables, even if there are <tt/condes/ entries in the object files.
-For more information see the <tt/.CONDES/ command in the <htmlurl
+For more information see the <tt/.CONDES/ command in the <url
url="ca65.html" name="ca65 manual">.
+<sect2>The STARTADDRESS feature<p>
-<sect1>Builtin configurations<label id="builtin-configs"><p>
-
-Here is a list of the builin configurations for the different target
-types:
-
-<descrip>
-<tag><tt>none</tt></tag>
-<tscreen><verb>
- MEMORY {
- RAM: start = %S, size = $10000, file = %O;
- }
- SEGMENTS {
- CODE: load = RAM, type = rw;
- RODATA: load = RAM, type = rw;
- DATA: load = RAM, type = rw;
- BSS: load = RAM, type = bss, define = yes;
- }
- FEATURES {
- CONDES: segment = RODATA,
- type = constructor,
- label = __CONSTRUCTOR_TABLE__,
- count = __CONSTRUCTOR_COUNT__;
- CONDES: segment = RODATA,
- type = destructor,
- label = __DESTRUCTOR_TABLE__,
- count = __DESTRUCTOR_COUNT__;
- }
- SYMBOLS {
- __STACKSIZE__ = $800; # 2K stack
- }
-</verb></tscreen>
-
-<tag><tt>atari</tt></tag>
-<tscreen><verb>
- MEMORY {
- ZP: start = $82, size = $7E, type = rw;
- HEADER: start = $0000, size = $6, file = %O;
- RAM: start = $1F00, size = $9D1F, file = %O; # $9D1F: matches upper bound $BC1F
- }
- SEGMENTS {
- EXEHDR: load = HEADER, type = wprot;
- CODE: load = RAM, type = wprot, define = yes;
- RODATA: load = RAM, type = wprot;
- DATA: load = RAM, type = rw;
- BSS: load = RAM, type = bss, define = yes;
- ZEROPAGE: load = ZP, type = zp;
- AUTOSTRT: load = RAM, type = wprot;
- }
- FEATURES {
- CONDES: segment = RODATA,
- type = constructor,
- label = __CONSTRUCTOR_TABLE__,
- count = __CONSTRUCTOR_COUNT__;
- CONDES: segment = RODATA,
- type = destructor,
- label = __DESTRUCTOR_TABLE__,
- count = __DESTRUCTOR_COUNT__;
- }
- SYMBOLS {
- __STACKSIZE__ = $800; # 2K stack
- }
-</verb></tscreen>
+<tt/STARTADDRESS/ is used to set the default value for the start address,
+which can be referenced by the <tt/%S/ symbol. The builtin default for the
+linker is $200.
-<tag><tt>atmos</tt></tag>
<tscreen><verb>
- MEMORY {
- ZP: start = $02, size = $1A, type = rw, define = yes;
- RAM: start = $0600, size = $9200, define = yes, file = %O;
- }
- SEGMENTS {
- CODE: load = RAM, type = wprot;
- RODATA: load = RAM, type = wprot;
- DATA: load = RAM, type = rw;
- BSS: load = RAM, type = bss, define = yes;
- ZEROPAGE: load = ZP, type = zp;
- }
FEATURES {
- CONDES: segment = RODATA,
- type = constructor,
- label = __CONSTRUCTOR_TABLE__,
- count = __CONSTRUCTOR_COUNT__;
- CONDES: segment = RODATA,
- type = destructor,
- label = __DESTRUCTOR_TABLE__,
- count = __DESTRUCTOR_COUNT__;
- }
- SYMBOLS {
- __STACKSIZE__ = $800; # 2K stack
+ # Default start address is $1000
+ STARTADDRESS: default = $1000;
}
</verb></tscreen>
-<tag><tt>c16</tt></tag>
-<tscreen><verb>
- MEMORY {
- ZP: start = $02, size = $1A, type = rw;
- RAM: start = $0fff, size = $7001, file = %O;
- }
- SEGMENTS {
- CODE: load = RAM, type = wprot;
- RODATA: load = RAM, type = wprot;
- DATA: load = RAM, type = rw;
- BSS: load = RAM, type = bss, define = yes;
- ZEROPAGE: load = ZP, type = zp;
- }
- FEATURES {
- CONDES: segment = RODATA,
- type = constructor,
- label = __CONSTRUCTOR_TABLE__,
- count = __CONSTRUCTOR_COUNT__;
- CONDES: segment = RODATA,
- type = destructor,
- label = __DESTRUCTOR_TABLE__,
- count = __DESTRUCTOR_COUNT__;
- }
- SYMBOLS {
- __STACKSIZE__ = $800; # 2K stack
- }
-</verb></tscreen>
+Please note that order is important: The default start address must be defined
+<em/before/ the <tt/%S/ symbol is used in the config file. This does usually
+mean, that the <tt/FEATURES/ section has to go to the top of the config file.
-<tag><tt>c64</tt></tag>
-<tscreen><verb>
- MEMORY {
- ZP: start = $02, size = $1A, type = rw;
- RAM: start = $7FF, size = $c801, define = yes, file = %O;
- }
- SEGMENTS {
- CODE: load = RAM, type = wprot;
- RODATA: load = RAM, type = wprot;
- DATA: load = RAM, type = rw;
- BSS: load = RAM, type = bss, define = yes;
- ZEROPAGE: load = ZP, type = zp;
- }
- FEATURES {
- CONDES: segment = RODATA,
- type = constructor,
- label = __CONSTRUCTOR_TABLE__,
- count = __CONSTRUCTOR_COUNT__;
- CONDES: segment = RODATA,
- type = destructor,
- label = __DESTRUCTOR_TABLE__,
- count = __DESTRUCTOR_COUNT__;
- }
- SYMBOLS {
- __STACKSIZE__ = $800; # 2K stack
- }
-</verb></tscreen>
-<tag><tt>c128</tt></tag>
-<tscreen><verb>
- MEMORY {
- ZP: start = $02, size = $1A, type = rw;
- RAM: start = $1bff, size = $a401, define = yes, file = %O;
- }
- SEGMENTS {
- CODE: load = RAM, type = wprot;
- RODATA: load = RAM, type = wprot;
- DATA: load = RAM, type = rw;
- BSS: load = RAM, type = bss, define = yes;
- ZEROPAGE: load = ZP, type = zp;
- }
- FEATURES {
- CONDES: segment = RODATA,
- type = constructor,
- label = __CONSTRUCTOR_TABLE__,
- count = __CONSTRUCTOR_COUNT__;
- CONDES: segment = RODATA,
- type = destructor,
- label = __DESTRUCTOR_TABLE__,
- count = __DESTRUCTOR_COUNT__;
- CONDES: segment = RODATA,
- type = 2,
- label = __IRQFUNC_TABLE__,
- count = __IRQFUNC_COUNT__;
- }
- SYMBOLS {
- __STACKSIZE__ = $800; # 2K stack
- }
-</verb></tscreen>
-<tag><tt>plus4</tt></tag>
-<tscreen><verb>
- MEMORY {
- ZP: start = $02, size = $1A, type = rw;
- RAM: start = $0fff, size = $7001, file = %O;
- }
- SEGMENTS {
- CODE: load = RAM, type = wprot;
- RODATA: load = RAM, type = wprot;
- DATA: load = RAM, type = rw;
- BSS: load = RAM, type = bss, define = yes;
- ZEROPAGE: load = ZP, type = zp;
- }
- FEATURES {
- CONDES: segment = RODATA,
- type = constructor,
- label = __CONSTRUCTOR_TABLE__,
- count = __CONSTRUCTOR_COUNT__;
- CONDES: segment = RODATA,
- type = destructor,
- label = __DESTRUCTOR_TABLE__,
- count = __DESTRUCTOR_COUNT__;
- }
- SYMBOLS {
- __STACKSIZE__ = $800; # 2K stack
- }
-</verb></tscreen>
+<sect1>The SYMBOLS section<label id="SYMBOLS"><p>
-<tag><tt>cbm510</tt></tag>
-<tscreen><verb>
- MEMORY {
- ZP: start = $02, size = $1A, type = rw;
- RAM: start = $0001, size = $F3FF, file = %O;
- VIDRAM: start = $F400, size = $0400, define = yes, file = "";
- }
- SEGMENTS {
- CODE: load = RAM, type = wprot;
- RODATA: load = RAM, type = wprot;
- DATA: load = RAM, type = rw;
- BSS: load = RAM, type = bss, define = yes;
- ZEROPAGE: load = ZP, type = zp;
- }
- FEATURES {
- CONDES: segment = RODATA,
- type = constructor,
- label = __CONSTRUCTOR_TABLE__,
- count = __CONSTRUCTOR_COUNT__;
- CONDES: segment = RODATA,
- type = destructor,
- label = __DESTRUCTOR_TABLE__,
- count = __DESTRUCTOR_COUNT__;
- CONDES: segment = RODATA,
- type = 2,
- label = __IRQFUNC_TABLE__,
- count = __IRQFUNC_COUNT__;
- }
- SYMBOLS {
- __STACKSIZE__ = $781; # ~2K stack
- }
-</verb></tscreen>
+The configuration file may also be used to define symbols used in the link
+stage or to force symbols imports. This is done in the SYMBOLS section. The
+symbol name is followed by a colon and symbol attributes.
-<tag><tt>cbm610</tt></tag>
-<tscreen><verb>
- MEMORY {
- ZP: start = $02, size = $1A, type = rw;
- RAM: start = $0001, size = $FFF0, file = %O;
- }
- SEGMENTS {
- CODE: load = RAM, type = wprot;
- RODATA: load = RAM, type = wprot;
- DATA: load = RAM, type = rw;
- BSS: load = RAM, type = bss, define = yes;
- ZEROPAGE: load = ZP, type = zp;
- }
- FEATURES {
- CONDES: segment = RODATA,
- type = constructor,
- label = __CONSTRUCTOR_TABLE__,
- count = __CONSTRUCTOR_COUNT__;
- CONDES: segment = RODATA,
- type = destructor,
- label = __DESTRUCTOR_TABLE__,
- count = __DESTRUCTOR_COUNT__;
- }
- SYMBOLS {
- __STACKSIZE__ = $800; # 2K stack
- }
-</verb></tscreen>
+The following symbol attributes are supported:
-<tag><tt>pet</tt></tag>
-<tscreen><verb>
- MEMORY {
- ZP: start = $02, size = $1A, type = rw;
- RAM: start = $03FF, size = $7BFF, file = %O;
- }
- SEGMENTS {
- CODE: load = RAM, type = wprot;
- RODATA: load = RAM, type = wprot;
- DATA: load = RAM, type = rw;
- BSS: load = RAM, type = bss, define = yes;
- ZEROPAGE: load = ZP, type = zp;
- }
- FEATURES {
- CONDES: segment = RODATA,
- type = constructor,
- label = __CONSTRUCTOR_TABLE__,
- count = __CONSTRUCTOR_COUNT__;
- CONDES: segment = RODATA,
- type = destructor,
- label = __DESTRUCTOR_TABLE__,
- count = __DESTRUCTOR_COUNT__;
- }
- SYMBOLS {
- __STACKSIZE__ = $800; # 2K stack
- }
-</verb></tscreen>
+<descrip>
-<tag><tt>apple2</tt></tag>
-<tscreen><verb>
- MEMORY {
- ZP: start = $00, size = $1A, type = rw;
- RAM: start = $800, size = $8E00, file = %O;
- }
- SEGMENTS {
- CODE: load = RAM, type = ro;
- RODATA: load = RAM, type = ro;
- DATA: load = RAM, type = rw;
- BSS: load = RAM, type = bss, define = yes;
- ZEROPAGE: load = ZP, type = zp;
- }
- FEATURES {
- CONDES: segment = RODATA,
- type = constructor,
- label = __CONSTRUCTOR_TABLE__,
- count = __CONSTRUCTOR_COUNT__;
- CONDES: segment = RODATA,
- type = destructor,
- label = __DESTRUCTOR_TABLE__,
- count = __DESTRUCTOR_COUNT__;
- }
- SYMBOLS {
- __STACKSIZE__ = $800; # 2K stack
- }
-</verb></tscreen>
+ <tag><tt>addrsize</tt></tag>
+
+ The <tt/addrsize/ attribute specifies the address size of the symbol and
+ may be one of
+<itemize>
+ <item><tt/zp/, <tt/zeropage/ or <tt/direct/
+ <item><tt/abs/, <tt/absolute/ or <tt/near/
+ <item><tt/far/
+ <item><tt/long/ or <tt/dword/.
+</itemize>
+
+Without this attribute, the default address size is <tt/abs/.
+
+ <tag><tt>type</tt></tag>
+
+ This attribute is mandatory. Its value is one of <tt/export/, <tt/import/ or
+ <tt/weak/. <tt/export/ means that the symbol is defined and exported from
+ the linker config. <tt/import/ means that an import is generated for this
+ symbol, eventually forcing a module that exports this symbol to be included
+ in the output. <tt/weak/ is similar as <tt/export/. However, the symbol is
+ only defined if it is not defined elsewhere.
+
+ <tag><tt>value</tt></tag>
+
+ This must only be given for symbols of type <tt/export/ or <tt/weak/. It
+ defines the value of the symbol and may be an expression.
+
+</descrip>
+
+The following example defines the stack size for an application, but allows
+the programmer to override the value by specifying <tt/--define
+__STACKSIZE__=xxx/ on the command line.
-<tag><tt>geos</tt></tag>
<tscreen><verb>
- MEMORY {
- HEADER: start = $204, size = 508, file = %O;
- RAM: start = $400, size = $5C00, file = %O;
- }
- SEGMENTS {
- HEADER: load = HEADER, type = ro;
- CODE: load = RAM, type = ro;
- RODATA: load = RAM, type = ro;
- DATA: load = RAM, type = rw;
- BSS: load = RAM, type = bss, define = yes;
- }
- FEATURES {
- CONDES: segment = RODATA,
- type = constructor,
- label = __CONSTRUCTOR_TABLE__,
- count = __CONSTRUCTOR_COUNT__;
- CONDES: segment = RODATA,
- type = destructor,
- label = __DESTRUCTOR_TABLE__,
- count = __DESTRUCTOR_COUNT__;
- }
- SYMBOLS {
- __STACKSIZE__ = $800; # 2K stack
- }
+ SYMBOLS {
+ # Define the stack size for the application
+ __STACKSIZE__: type = weak, value = $800;
+ }
</verb></tscreen>
-</descrip>
-The "<tt/start/" attribute for the <tt/RAM/ memory area of the CBM systems is
-two less than the actual start of the basic RAM to account for the two bytes
-load address that is needed on disk and supplied by the startup code.
+<sect>Special segments<p>
+
+The builtin config files do contain segments that have a special meaning for
+the compiler and the libraries that come with it. If you replace the builtin
+config files, you will need the following information.
+<sect1>ONCE<p>
-<sect>Bugs/Feedback<p>
+The ONCE segment is used for initialization code run only once before
+execution reaches main() - provided that the program runs in RAM. You
+may for example add the ONCE segment to the heap in really memory
+constrained systems.
-If you have problems using the linker, if you find any bugs, or if you're
-doing something interesting with it, I would be glad to hear from you. Feel
-free to contact me by email (<htmlurl url="mailto:uz@cc65.org"
-name="uz@cc65.org">).
+<sect1>LOWCODE<p>
+
+For the LOWCODE segment, it is guaranteed that it won't be banked out, so it
+is reachable at any time by interrupt handlers or similar.
+
+<sect1>STARTUP<p>
+
+This segment contains the startup code which initializes the C software stack
+and the libraries. It is placed in its own segment because it needs to be
+loaded at the lowest possible program address on several platforms.
+
+<sect1>ZPSAVE<p>
+
+The ZPSAVE segment contains the original values of the zeropage locations used
+by the ZEROPAGE segment. It is placed in its own segment because it must not be
+initialized.
<sect>Copyright<p>
-ld65 (and all cc65 binutils) are (C) Copyright 1998-2001 Ullrich von
+ld65 (and all cc65 binutils) are (C) Copyright 1998-2005 Ullrich von
Bassewitz. For usage of the binaries and/or sources the following
conditions do apply:
freely, subject to the following restrictions:
<enum>
-<item> The origin of this software must not be misrepresented; you must not
- claim that you wrote the original software. If you use this software
- in a product, an acknowledgment in the product documentation would be
- appreciated but is not required.
-<item> Altered source versions must be plainly marked as such, and must not
- be misrepresented as being the original software.
-<item> This notice may not be removed or altered from any source
- distribution.
+<item> The origin of this software must not be misrepresented; you must not
+ claim that you wrote the original software. If you use this software
+ in a product, an acknowledgment in the product documentation would be
+ appreciated but is not required.
+<item> Altered source versions must be plainly marked as such, and must not
+ be misrepresented as being the original software.
+<item> This notice may not be removed or altered from any source
+ distribution.
</enum>
</article>
-
projects / cc65 / blobdiff