TADS 3 provides "separate compilation," which means that you can arrange your program's source code into several modules, each of which is compiled separately from the others, then link together the compiled modules into a finished program.
Previous versions of TADS provided a related feature, called "precompiled headers," that allowed you to compile part of your program's source code ahead of time. This wasn't nearly as powerful as TADS 3's true separate compilation, however: precompiled headers only let you pre-compile a single section of the code, which meant that any change to the single pre-compiled section required full recompilation. TADS 3's true separate compilation lets you structure your code into as many separate files as you want, each of which can be independently compiled; you only need to recompile the sections you actually change.
The TADS 3 compiler includes a "make" facility, which automatically recompiles the source modules that you've changed since they were last compiled. The TADS 3 "make" facility is similar to the Unix "make" program, but is not programmable like the Unix version; instead, the TADS 3 version is pre-programmed with the relationships among source, object, and image files.
To build a program using TADS 3, you run the "make" command, t3make, with all of the source modules listed as arguments. You do not need to use #include to combine the source modules from a master source file as you did in previous versions; instead, the linker combines the modules together for you. (You can still use #include to structure your program as a single logical module if you want, but if you do so you will not gain the advantages of separate compilation.)
t3make first compiles each source file that has been modified since it was last compiled. The result of compiling a source module is an "object file"; a source file called "mygame.t" would have a corresponding object file called "mygame.t3o" – "t3o" stands for "T3 Object." If a source file or one of its included files has been modified since the corresponding object file was created, t3make compiles the source file; if the object file is up to date with the source, there's no need to recompile the source file, so t3make automatically skips it.
Note that the "object" in "object file" doesn't mean a code object, as in an instance of a class. "Object file" is a term that most compiled languages use to refer to the output of the compiler, which is also the input to the linker. An object file contains a version of the source program that has been translated into machine code, but which usually contains references to external symbols that must be resolved by the linker before the code becomes an executable program.
After compiling all of the modified source files into object files, t3make looks to see if the image file is up to date by checking to see if any object files are newer. If at least one object file is newer than the image file, the image file must be re-linked. (Thus, if any source files are compiled during this run of t3make, the image will obviously have to be re-linked.) If it is necessary to re-link, t3make loads all of the object files, resolves their mutual external references, and creates an image file.
The biggest advantage of separate compilation is that loading an object file into the linker is usually much faster than compiling a source file. If you're working on a large game, you will often make changes in only a few parts at a time, which means that only a small number of your source files might need to be compiled for each build. This can often speed up building quite substantially.
The t3make command line looks like this:
t3make –o mygame.t3 –Fo obj –Fy sym game1.t game2.t game3.t
The -o option tells the linker the name of the image file; this is the T3 executable file that you run using the TADS 3 interpreter. The -Fo option, if you include it, tells the compiler where to put object files; by default, they'll go in the same place as the source file, but if you want to store object files in a separate directory, which you might wish to do to keep your source directory uncluttered, you can use this option. Similarly, the -Fy option tells the compiler where to put "symbol" files, which are another kind of generated file that the compiler creates; as with objects, you might want to keep these files in a separate directory from the source to avoid clutter. (You don't otherwise need to worry about symbol files; they're purely for the compiler's use.) Finally, you must list the source files that make up your game.
Other options that might be useful from time to time:
After the options, you list all of the source modules involved in the compilation. Each source module can be a regular source file (a ".t" file), or it can be a "library" file, as explained below. The compiler attempts to infer the type of each file by checking its filename suffix: if the suffix is ".tl", the compiler assumes that the file is a library, otherwise it assumes it is a source file. If you do not use the conventional filename suffixes for your source and library files, you can explicitly tell the compiler the type each file by prefixing each file with a "-source" or "-lib" option. For example:
t3make -o mygame.t3 -source game1.tads -lib mylib.tadslib
Note that the "-source" and "-lib" type specifiers are not actually options; these can't be mixed in with the regular options, but can only appear in the module list portion of the command line, which follows all of the options.
Note also that the compiler treats the "-" prefix as special everywhere in the command line. This means that if the name of one of your source files actually starts with "-", you must put a "-source" specifier immediately before that filename, even if it ends with the conventional suffix, because otherwise the compiler would be confused into thinking the filename was meant as a type specifier.
Immediately following the name of a library, you can list one or more "-x" options to exclude modules that the library includes. This is explained below.
It's often useful to take a set of source files and group them together as though they were a unit. For example, the standard Adventure Library included with TADS consists of a number of separate source files; for the most part you don't want to have to think about which individual files are involved - you just want to include the entire Adventure Library as a unit.
The compiler has a mechanism to simplify working with groups of files like this: you can create a separate, special kind of file that lists the regular source files that make up the group, and then include only this special listing file in your compilation. The compiler automatically reads the list of files from the special file. This special file is called a "library file" (not to be confused with the more generic usage of "library" that refers to a group of files the provide reusable source code, such as the Adventure Library - a library file is a specially formatted file that specifies a group of source files to include in a compilation).
By convention, a library filename always has the suffix ".tl" (but note that the period might be replaced with another character on some platforms, and some platforms don't use filename suffixes at all).
The compiler automatically adds each library’s directory to the include path. If you’re distributing a library, this means that you can bundle all of your library’s files together into a single directory, and the user will only have to specify the path to your library’s install directory once, when listing the .tl file on the compiler command line.
A library file is simply a text file that obeys a specific format. A library file is formatted with one definition per line (blank lines are ignored, as are lines starting with the comment character "#"). A definition has this format:
keyword: value
The "keyword" is a word specifying what kind of information the line contains, and the "value" is the text of the information defined. The valid keywords are:
The values for the source and library keywords are filenames, given in a portable format. You must not specify a filename extension (such as ".t") on these values, because the compiler adds the appropriate extension for the local platform automatically. You must use slash ("/") characters to indicate directory path separators; the compiler automatically converts the "/" characters to the appropriate local conventions. If you specify any directory paths, you must specify only relative paths that are subdirectories of the folder containing the library; you are not allowed to specify absolute paths, and you are not allowed to use ".." or other OS-specific conventions to refer to parent directories. If you follow all of these conventions, you will ensure that your library files will be portable to all operating systems, so that other people using different operating systems won't have to modify your library files for their local conventions.
When the compiler reads a library file, it converts each source and library value to local conventions. The compiler makes the following changes to each name:
Here's an example of a library file:
name: Calculator Library
source: display
source: keypad
source: arith
source: sci
source: trig
This library has the display name "Calculator Library", and includes five source files: display.t, keypad.t, arith.t, sci.t, and trig.t. Assuming you called this library "calc.tl", you would include the library in a compilation like so:
t3make -d -lib calc.tl mygame.t
Sometimes, a library includes non-essential files that you don't need in your program. For example, a library might have some extended functionality that it includes for those programs that want it, but which can be omitted by programs that don't use it. Including extraneous code is generally not harmful, but it does unnecessarily increase the size of your program's compiled image file and its run-time memory needs, so it's best to avoid adding code you're not using.
The obvious way of eliminating unneeded code would be to edit the library file itself to remove the modules you don't need. This isn't ideal, though, because it would remove those modules from other projects you're working on that might need the extra code. To solve this problem, you could simply create a copy of the library file and remove the unneeded modules from it. This creates another problem, though: if you got the library file from someone else, and they later change the library by renaming a source file or adding or removing files, you'd have to make the same changes to your copy or copies of the library.
Fortunately, there's a way to exclude files from a library without changing the library itself. When you include a library on the compiler command line, the compiler lets you list one or more files to exclude, using "-x" specifiers. A "-x" specifier must be placed on the compiler command line immediately after the library to which it applies. Each "-x" is followed by the name of a source module to exclude, using the name as it appears in the library - that is, using the portable name format, without an extension and with "/" as the path separator. Simply use the exact text of the source value as it appears in the library file.
Note that you cannot exclude an entire sub-library from a library. If a library includes a sub-library, you must exclude the files from the sub-library individually. To do so, treat the sub-library name as a path prefix, and place a "/" after the sub-library name, then add the filename as it appears in the sub-library. For example, suppose that another library, desk.tl, includes the calc.tl library as a sub-library:
# desk accessory library
name: Desk Accessory Library
library: pen
library: pencil
library: calc
Now, suppose you compile a program including the desk.tl library, but you want to exclude the trig.t module included in the calc.tl library. To do this, you'd write a "-x" option like this:
t3make desk.tl -x calc/trig
If you take advantage of the separate compilation capability by dividing your program into several source files, you might find that your t3make command lines become quite lengthy. This will be of no concern if you're using an integrated environment such as TADS Workbench, but could become inconvenient if you're building directly from a command shell.
To make things easier for command-line users, t3make can read build commands from an "option file." An option file is simply a text file that contains the same information you'd normally put on the command line. Each line of an option file can include one or more module names and options, separated by spaces. Use a pound sign ("#") to start a comment; everything after a pound sign is ignored. If you want to use spaces or pound signs within a filename or option, enclose the entire option in double quotes; if you want to use a double quote mark within a quoted option, use two double quote marks.
Here's a sample option file.
#
# option file for calc
#
# source files
"calc sources\calc.t"
"tok sources\tok.t"
# image file
-o "exe\calc.t3o"
To read options from a file, use the –f compiler option:
t3make –f calc.t3m
The options read from an options file are appended after the options on the command line, so you can mix options from a file and the command line. For example, if you wanted to use the option file above to compile the program for debugging, you could enter a command like this:
t3make –f calc.t3m -d
If you run t3make and do not specify any modules (in other words, your command line consists only of options), and you also don't include a –f option to specify an option file, the compiler looks for a default option file called "makefile.t3m" in the current directory. If this file is present, the compiler reads the file as though you had specified it with the –f option. This makes it very easy to build your program; if you put your build options in the file makefile.t3m, you can build simply by typing "t3make".
The normal rules for option files apply to makefile.t3m, so you can specify additional options on the command line when building with the default option file. For example, to build for debugging using the default option file, you would simply enter this:
t3make –d
TADS 3 includes a default source module called _main.t that contains some low-level support code that most programs need. Because most programs will not have any reason to customize this module, the compiler automatically includes the module; this saves you a little work, because you don't have to add the module to your t3make command line explicitly.
However, it is possible that you'll want to use a different version of the code in _main.t, in which case you will need to remove the default version from the build. To do this, use the compiler's –nodef option. This option tells the compiler not to include any default modules in the build; only the modules you explicitly list on the command line (or in an option file) are included in the build in this case.
Include files: The compiler automatically adds the default system header directory to the end of the include file search path. In effect, the compiler adds a -I option, after all user-specified -I options, specifying the system header directory. The location of the system header directory varies by system; on DOS and Windows, this is the directory containing the compiler. Refer to your system-specific release notes for details on other systems.
Source files: The compiler automatically adds the default system library source directory to the end of the source file search path. In effect, the compiler adds a -Fs option, after all user-specified -Fs options, specifying the system library source directory. The location of this directory varies by system; on DOS and Windows, this is the compiler install directory. Refer to your system-specific release notes for details on other systems.
The t3make utility will compile a source file if it finds any of the following conditions:
The dependency tracking mechanism isn't perfect, and it can be fooled under certain circumstances:
You can force a full recompilation with the t3make –r option; you can use this option if you encounter any situations where you suspect that t3make is missing some dependency and therefore failing to notice a file that requires recompilation.