cc65 compiler intro <author>Ullrich von Bassewitz, <htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org"> <date>03.12.2000 <abstract> How to use the cc65 C compiler - an introduction. </abstract>  <toc>  <sect>Overview This is a short intro, how to use the compiler and the binutils. It contains a step-by-step example, how to build a complete application from one C and one assembler module. This file does <em/not/ contain a complete reference for the tools used in the process. There are separate files describing these tools in detail. <bf>Note</bf>: There is a much simpler way to compile this example using the cl65 compiler and link utility. However, it makes sense to understand how the separate steps work. How to do the example with the cl65 utility is described <ref id="using-cl65" name="below">. <sect1>The sample modules To explain the development flow, I will use the following example modules: hello.c: <tscreen><code> #include <stdio.h> #include <stdlib.h> extern const char text[]; /* In text.s */ int main (void) { printf ("%s\n", text); return EXIT_SUCCESS; } </code></tscreen> text.s: <tscreen><code> .export _text _text: .asciiz "Hello world!" </code></tscreen> <sect1>Translation phases We assume that the target file should be named "hello", and the target system is the C64. <tscreen><verb> +---------+ | hello.c | +---------+ | cc65 \/ +---------+ +---------+ | hello.s | | text.s | +---------+ +---------+ | | ca65 ca65 \/ \/ +---------+ +---------+ +----------+ +---------+ | hello.o | | text.o | | c64.o | | c64.lib | +---------+ +---------+ +----------+ +---------+ | \ / | | \ / | | \ / | +----------------------->ld65<-------------------------+ \/ hello </verb></tscreen> <tt/c64.o/ (the startup code) and <tt/c64.lib/ (the c64 version of the runtime and C library) are provided in binary form in the cc65 package. <sect>The compiler The compiler translates one C source into one assembler source for each invocation. It does <em/not/ create object files directly, and it is <em/not/ able to translate more than one file per run. In the example above, we would use the following command line, to translate <tt/hello.c/ into <tt/hello.s/: <tscreen><verb> cc65 -O -I ../include -t c64 hello.c </verb></tscreen> The <tt/-O/ switch tells the compiler to do an additional optimizer run, which is usually a good idea, since it makes the code smaller. If you don't care about the size, but want to have slightly faster code, use <tt/-Oi/ to inline some runtime functions. The <tt/-I/ switch gives a search path for the include files. You may also set the environment variable CC65_INC to the search path. The <tt/-t/ switch is followed by the target system. If the compiler does not complain about errors in our hello world, we will have a file named "<tt/hello.s/" in our directory that contains the assembler source for the hello module. For more information about the compiler see <htmlurl url="cc65.html" name="cc65.html">. <sect>The assembler The assembler translates one assembler source into an object file for each invocation. The assembler is <tt/not/ able to translate more than one source file per run. Let's translate the hello.s and text.s files from our example: <tscreen><verb> ca65 hello.s ca65 -t c64 text.s </verb></tscreen> The <tt/-t/ switch is needed when translating the <tt/text.s/ file, so the text is converted from the input character set (usually ISO-8859-1) into the target character set (PETSCII) by the assembler. The compiler generated file <tt/hello.s/ does not contain any character constants, so specification of a target is not necessary (it wouldn't do any harm, however). If the assembler does not complain, we should now have two object files (named <tt/hello.o/ and <tt/text.o/) in the current directory. For more information about the assembler see <htmlurl url="ca65.html" name="ca65.html">. <sect>The linker The linker combines several object and library file into one output file. ld65 is very configurable, but fortunately has a builtin configuration for the C64, so we don't need to mess with configuration files here. The compiler uses small functions to do things that cannot be done inline without big impact on code size. These runtime functions, together with the C library are in an object file archive named after the system, in this case "<tt/c64.lib/". We have to specify this file on the command line so that the linker can resolve these functions. A second file (this time an object file) needed, is the startup code that prepares the grounds for the C program to run. The startup file must be executed first, so it must be the first file on the linker command line. Let's link our files to get the final executable: <tscreen><verb> ld65 -t c64 -o hello c64.o hello.o text.o c64.lib </verb></tscreen> The argument after <tt/-o/ specifies the name of the output file, the argument after <tt/-t/ gives the target system. As discussed, the startup file must be the first file on the command line (you may have to add a path here, if <tt/c64.o/ is not in your current directory). Since the library resolves imports in <tt/hello.o/ and <tt/text.o/, it must be specified <em/after/ these files. After a successful linker run, we have a file named "<tt/hello/", ready for our C64! For more information about the linker see <htmlurl url="ld65.html" name="ld65.html">. <sect>The easy way (using the cl65 utility)<label id="using-cl65"> The cl65 utility is able to do all of the steps described above in just one call, and it has defaults for some options that are very well suited for our example. To compile both files into one executable enter <tscreen><verb> cl65 -O -I ../include hello.c test.s </verb></tscreen> (The <tt/-I/ switch is not needed if you are working under Linux with the include files in the default path, or the <tt/CC65_INC/ environment variable is set correctly). The cl65 utility knows, how to translate C files into object files (it will call the compiler and then the assembler). It does also know how to create object files from assembler files (it will call the assember for that). It knows how to build an executable (it will pass all object files to the linker). And, finally, it has the C64 as a default target and will supply the correct startup file and runtime library names to the linker, so you don't have to care about that. The one-liner above should give you a C64 executable named "<tt/hello/" in the current directory. For more information about the compile & link utility see <htmlurl url="cl65.html" name="cl65.html">. </article>