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Comment:	Cherrypick [9b960af129], was supposed to have been checked into trunk in the first place
Downloads:	Tarball \| ZIP archive \| SQL archive
Timelines:	family \| ancestors \| descendants \| both \| trunk
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SHA1:	bbafc013aa7348f836ccdbfd0c8935dafdc2b15f
User & Date:	andygoth 2016-11-04 23:18:01

Context

2016-11-04
23:57		Use linenoise for fossil shell. Do not bother with persistent history. (check-in: 6327b026 user: andygoth tags: trunk)
23:18		Cherrypick [9b960af129], was supposed to have been checked into trunk in the first place (check-in: bbafc013 user: andygoth tags: trunk)
23:13		Fix various typos in makeheaders.html. Use curly quotes instead of classic `` and '' quotes (ref: http://www.dwheeler.com/essays/quotes-in-html.html). Format most such quoted text in monospace print. (check-in: 9b960af1 user: andygoth tags: andygoth-timeline-ms)
22:37		Consistently use the count(X) macro in place of sizeof(X)/sizeof(*X) throughout the Fossil core, excluding things that don't use makeheaders. Also use count(X) instead of ArraySize(X) which has the same definition. (check-in: e5b62edb user: andygoth tags: trunk)

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<head><title>The Makeheaders Program</title></head>
<body bgcolor=white>
<h1 align=center>The Makeheaders Program</h1>


<p>
This document describes <em>makeheaders</em>,
a tool that automatically generates ``<code>.h</code>''
files for a C or C++ programming project.
</p>


<h2>Table Of Contents</h2>

<ul>
................................................................................
<p>
Declarations in C include things such as the following:
<ul>
<li> Typedefs.
<li> Structure, union and enumeration declarations.
<li> Function and procedure prototypes.
<li> Preprocessor macros and #defines.
<li> ``extern'' variable declarations.
</ul>
</p>

<p>
Definitions in C, on the other hand, include these kinds of things:
<ul>
<li> Variable definitions.
................................................................................
modern software engineering.
Another way of looking at the difference is that the declaration
is the <em>interface</em> and the definition is the <em>implementation</em>.
</p>

<p>
In C programs, it has always been the tradition that declarations are
put in files with the ``<code>.h</code>'' suffix and definitions are
placed in ``<code>.c</code>'' files.
The .c files contain ``<code>#include</code>'' preprocessor statements
that cause the contents of .h files to be included as part of the
source code when the .c file is compiled.
In this way, the .h files define the interface to a subsystem and
the .c files define how the subsystem is implemented.
</p>

<a name="H0003"></a>
................................................................................
into the file of your choice.
</p>

<p>
A similar option is -H.  Like the lower-case -h option, big -H
generates a single include file on standard output.  But unlike
small -h, the big -H only emits prototypes and declarations that
have been designated as ``exportable''.
The idea is that -H will generate an include file that defines
the interface to a library.
More will be said about this in section 3.4.
</p>

<p>
Sometimes you want the base name of the .c file and the .h file to
................................................................................
If you want a particular file to be scanned by makeheaders but you
don't want makeheaders to generate a header file for that file,
then you can supply an empty header filename, like this:
<pre>
   makeheaders alpha.c beta.c gamma.c:
</pre>
In this example, makeheaders will scan the three files named
``alpha.c'',
``beta.c'' and
``gamma.c''
but because of the colon on the end of third filename
it will only generate headers for the first two files.
Unfortunately,
it is not possible to get makeheaders to process any file whose
name contains a colon.
</p>

<p>
In a large project, the length of the command line for makeheaders
can become very long.
If the operating system doesn't support long command lines
(example: DOS and Win32) you may not be able to list all of the
input files in the space available.
In that case, you can use the ``-f'' option followed
by the name of a file to cause makeheaders to read command line
options and filename from the file instead of from the command line.
For example, you might prepare a file named ``mkhdr.dat''
that contains text like this:
<pre>
  src/alpha.c:hdr/alpha.h
  src/beta.c:hdr/beta.h
  src/gamma.c:hdr/gamma.h
  ...
</pre>
................................................................................
Then invoke makeheaders as follows:
<pre>
  makeheaders -f mkhdr.dat
</pre>
</p>

<p>
The ``-local'' option causes makeheaders to
generate of prototypes for ``static'' functions and
procedures.
Such prototypes are normally omitted.
</p>

<p>
Finally, makeheaders also includes a ``-doc'' option.
This command line option prevents makeheaders from generating any
headers at all.
Instead, makeheaders will write to standard output
information about every definition and declaration that it encounters
in its scan of source files.
The information output includes the type of the definition or
declaration and any comment that preceeds the definition or
................................................................................
documentation about the program.
We'll talk more about this feature later.
</p>

<p>
If you forget what command line options are available, or forget
their exact name, you can invoke makeheaders using an unknown
command line option (like ``--help'' or ``-?'')

and it will print a summary of the available options on standard
error.
If you need to process a file whose name begins with ``-'',

you can prepend a ``./'' to its name in order to get it
accepted by the command line parser.
Or, you can insert the special option ``--'' on the command
line to cause all subsequent command line arguments to be treated as
filenames even if their names beginn with ``-''.
</p>

<a name="H0006"></a>
<h2>3.0 Preparing Source Files For Use With Makeheaders</h2>

<p>
Very little has to be done to prepare source files for use with
................................................................................
This section will describe several typical uses of makeheaders.
</p>

<a name="H0007"></a>
<h3>3.1 The Basic Setup</h3>

<p>
The simpliest way to use makeheaders is to put all definitions in
one or more .c files and all structure and type declarations in
separate .h files.
The only restriction is that you should take care to chose basenames
for your .h files that are different from the basenames for you
.c files.
Recall that if your .c file is named (for example) ``alpha.c''

makeheaders will attempt to generate a corresponding header file
named ``alpha.h''.

For that reason, you don't want to use that name for
any of the .h files you write since that will prevent makeheaders
from generating the .h file automatically.
</p>

<p>
The structure of a .c file intented for use with makeheaders is very
simple.
All you have to do is add a single ``#include'' to the top
of the file that sources the header file that makeheaders will generate.
Hence, the beginning of a source file named ``alpha.c''
might look something like this:
</p>

<pre>
   /*
    * Introductory comment...
    */
................................................................................
   /* The rest of your code... */
</pre>

<p>
Your manually generated header files require no special attention at all.
Code them as you normally would.
However, makeheaders will work better if you omit the
``#if'' statements people often put around the outside of
header files that prevent the files from being included more than once.
For example, to create a header file named ``beta.h'', many
people will habitually write the following:

<pre>
   #ifndef BETA_H
   #define BETA_H

   /* declarations for beta.h go here */

................................................................................

You can forego this cleverness with makeheaders.
Remember that the header files you write will never really be
included by any C code.
Instead, makeheaders will scan your header files to extract only
those declarations that are needed by individual .c files and then
copy those declarations to the .h files corresponding to the .c files.
Hence, the ``#if'' wrapper serves no useful purpose.
But it does make makeheaders work harder, forcing it to put
the statements

<pre>
   #if !defined(BETA_H)
   #endif
</pre>
................................................................................
manually written .h files and then automatically generate .h files
corresponding to all .c files.
</p>

<p>
Note that
the wildcard expression used in the above example,
``<code>*.[ch]</code>'',
will expand to include all .h files in the current directory, both
those entered manually be the programmer and others generated automatically
by a prior run of makeheaders.
But that is not a problem.
The makeheaders program will recognize and ignore any files it
has previously generated that show up on its input list.
</p>
................................................................................

<ul>
<p><li>
When a function is defined in any .c file, a prototype of that function
is placed in the generated .h file of every .c file that
calls the function.</p>

<P>If the ``static'' keyword of C appears at the beginning
of the function definition, the prototype is suppressed.
If you use the ``LOCAL'' keyword where you would normally
say ``static'', then a prototype is generated, but it
will only appear in the single header file that corresponds to the
source file containing the function.  For example, if the file
<code>alpha.c</code> contains the following:
<pre>
  LOCAL int testFunc(void){
    return 0;
  }
................................................................................
<pre>
  #define LOCAL static
  LOCAL int testFunc(void);
</pre>
However, no other generated header files will contain a prototype for
<code>testFunc()</code> since the function has only file scope.</p>

<p>When the ``LOCAL'' keyword is used, makeheaders will also
generate a #define for LOCAL, like this:
<pre>
   #define LOCAL static
</pre>
so that the C compiler will know what it means.</p>

<p>If you invoke makeheaders with a ``-local'' command-line
option, then it treats the ``static'' keyword like
``LOCAL'' and generates prototypes in the header file
that corresponds to the source file containing the function defintiion.</p>


<p><li>
When a global variable is defined in a .c file, an ``extern''

declaration of that variable is placed in the header of every
.c file that uses the variable.
</p>

<p><li>
When a structure, union or enumeration declaration or a
function prototype or a C++ class declaration appears in a
................................................................................
those files and are not copied.
</p>

<p><li>
When a structure, union or enumeration declaration appears in a .h
file, makeheaders will automatically
generate a typedef that allows the declaration to be referenced without
the ``struct'', ``union'' or ``enum''
qualifier.
In other words, if makeheaders sees the code:
<pre>
  struct Examp { /* ... */ };
</pre>
it will automatically generate a corresponding typedef like this:
<pre>
  typedef struct Examp Examp;
................................................................................
The .h files are suppose to contain only interface, not implementation.
C compilers will not enforce this convention, but makeheaders does.
</ul>

<p>
As a final note, we observe that automatically generated declarations
are ordered as required by the ANSI-C programming language.
If the declaration of some structure ``X'' requires a prior
declaration of another structure ``Y'', then Y will appear
first in the generated headers.
</p>

<a name="H0009"></a>
<h3>3.3 How To Avoid Having To Write Any Header Files</h3>

<p>
In my experience, large projects work better if all of the manually
................................................................................
You can instruct makeheaders to treat any part of a .c file as if
it were a .h file by enclosing that part of the .c file within:
<pre>
   #if INTERFACE
   #endif
</pre>
Thus any structure definitions that appear after the
``#if INTERFACE'' but before the corresponding
``#endif'' are eligable to be copied into the
automatically generated
.h files of other .c files.
</p>

<p>
If you use the ``#if INTERFACE'' mechanism in a .c file,
then the generated header for that .c file will contain a line
like this:
<pre>
   #define INTERFACE 0
</pre>
In other words, the C compiler will never see any of the text that
defines the interface.
................................................................................
putting the declarations in the correct ANSI-C order -- makeheaders
will do that for you automatically.
</p>

<p>
Note that you don't have to use this approach exclusively.
You can put some declarations in .h files and others within the
``#if INTERFACE'' regions of .c files.
Makeheaders treats all declarations alike, no matter where they
come from.
You should also note that a single .c file can contain as many
``#if INTERFACE'' regions as desired.
</p>

<a name="H0010"></a>
<h3>3.4 Designating Declarations For Export</h3>

<p>
In a large project, one will often construct a hierarchy of
................................................................................
(The second interface is normally a subset of the first.)
Ordinary C does not provide support for a tiered interface
like this, but makeheaders does.
</p>

<p>
Using makeheaders, it is possible to designate routines and data
structures as being for ``export''.
Exported objects are visible not only to other files within the
same library or subassembly but also to other
libraries and subassemblies in the larger program.
By default, makeheaders only makes objects visible to other members
of the same library.
</p>

................................................................................
This is not a perfect solution, but it works well in practice.
</p>

<p>
But trouble quickly arises when we attempt to devise a mechanism for
telling makeheaders which prototypes it should export and which it should
keep local.
The built-in ``static'' keyword of C works well for prohibiting
prototypes from leaving a single source file, but because C doesn't
support a linkage hierarchy, there is nothing in the C language to help us.
We'll have to invite our own keyword: ``EXPORT''
</p>

<p>
Makeheaders allows the EXPORT keyword to precede any function or
procedure definition.
The routine following the EXPORT keyword is then eligable to appear
in the header file generated using the -H command line option.
................................................................................
are visible to all files within the library, any declarations
or definitions within
<pre>
   #if EXPORT_INTERFACE
   #endif
</pre>
will become part of the exported interface.
The ``#if EXPORT_INTERFACE'' mechanism can be used in either
.c or .h files.
(The ``#if INTERFACE'' can also be used in both .h and .c files,
but since it's use in a .h file would be redundant, we haven't mentioned
it before.)
</p>

<a name="H0011"></a>
<h3>3.5 Local declarations processed by makeheaders</h3>

<p>
Structure declarations and typedefs that appear in .c files are normally
ignored by makeheaders.
Such declarations are only intended for use by the source file in which
they appear and so makeheaders doesn't need to copy them into any
generated header files.
We call such declarations ``private''.
</p>

<p>
Sometimes it is convenient to have makeheaders sort a sequence
of private declarations into the correct order for us automatically.
Or, we could have static functions and procedures for which we would like
makeheaders to generate prototypes, but the arguments to these
................................................................................
<p>
When this situation arises, enclose the private declarations
within
<pre>
  #if LOCAL_INTERFACE
  #endif
</pre>
A ``LOCAL_INTERFACE'' block works very much like the

``INTERFACE'' and ``EXPORT_INTERFACE''
blocks described above, except that makeheaders insures that the
objects declared in a LOCAL_INTERFACE are only visible to the
file containing the LOCAL_INTERFACE.
</p>

<a name="H0012"></a>
<h3>3.6 Using Makeheaders With C++ Code</h3>

<p>
You can use makeheaders to generate header files for C++ code, in
addition to C.
Makeheaders will recognize and copy both ``class'' declarations

and inline function definitions, and it knows not to try to generate
prototypes for methods.
</p>

<p>
In fact, makeheaders is smart enough to be used in projects that employ
a mixture of C and C++.
................................................................................
<p>
No special command-line options are required to use makeheaders with
C++ input.  Makeheaders will recognize that its source code is C++
by the suffix on the source code filename.  Simple ".c" or ".h" suffixes
are assumed to be ANSI-C.  Anything else, including ".cc", ".C" and
".cpp" is assumed to be C++.
The name of the header file generated by makeheaders is derived from
by the name of the source file by converting every "c" to "h" and
every "C" to "H" in the suffix of the filename.
Thus the C++ source
file ``alpha.cpp'' will induce makeheaders to
generate a header file named ``alpha.hpp''.
</p>

<p>
Makeheaders augments class definitions by inserting prototypes to
methods were appropriate.  If a method definition begins with one
of the special keywords <b>PUBLIC</b>, <b>PROTECTED</b>, or
<b>PRIVATE</b> (in upper-case to distinguish them from the regular
C++ keywords with the same meaning) then a prototype for that
method will be inserted into the class definition.  If none of
these keywords appear, then the prototype is not inserted.  For
example, in the following code, the constructor is not explicitly
declared in the class definition but makeheaders will add it there
................................................................................
</p>

<h4>3.6.1 C++ Limitations</h4>

<p>
Makeheaders does not understand more recent
C++ syntax such as templates and namespaces.
Perhaps these issued will be addressed in future revisions.
</p>

<a name="H0013"></a>
<h3>3.7 Conditional Compilation</h3>

<p>
The makeheaders program understands and tracks the conditional
compilation constructs in the source code files it scans.
Hence, if the following code appears in a source file
<pre>
  #ifdef UNIX
  #  define WORKS_WELL  1
  #else
  #  define WORKS_WELL  0
  #endif
</pre>
then the next patch of code will appear in the generated header for
every .c file that uses the WORKS_WELL constant:
<pre>
  #if defined(UNIX)
  #  define WORKS_WELL 1
................................................................................
</p>

<p>
Makeheaders does not understand the old K&amp;R style of function
and procedure definitions.
It only understands the modern ANSI-C style, and will probably
become very confused if it encounters an old K&amp;R function.
You should take care to avoid putting K&amp;R function defintions
in your code, therefore.
</p>

<p>
Makeheaders does not understand when you define more than one
global variable with the same type separated by a comma.
In other words, makeheaders does not understand this:
<pre>
................................................................................
     unrelated file in a different part of the source tree.
<li> Information is kept in only one place.  When a change occurs
     in the code, it is not necessary to make a corresponding change
     in a separate document.  Just rerun the documentation generator.
</ul>
The makeheaders program does not generate program documentation itself.
But you can use makeheaders to parse the program source code, extract
the information that is relavant to the documentation and to pass this
information to another tool to do the actual documentation preparation.
</p>

<p>
When makeheaders is run with the ``-doc'' option, it emits
no header files at all.
Instead, it does a complete dump of its internal tables to standard
outputs in a form that is easily parsed.
This output can then be used by another program (the implementation
of which is left as an exercise to the reader) that will use the
information to prepare suitable documentation.
</p>

<p>
The ``-doc'' option causes makeheaders to print information
to standard output about all of the following objects:
<ul>
<li> C++ Class declarations
<li> Structure and union declarations
<li> Enumerations
<li> Typedefs
<li> Procedure and function definitions
<li> Global variables
<li> Preprocessor macros (ex: ``#define'')
</ul>
For each of these objects, the following information is output:
<ul>
<li> The name of the object.
<li> The type of the object.  (Structure, typedef, macro, etc.)
<li> Flags to indicate if the declaration is exported (contained within
     an EXPORT_INTERFACE block) or local (contained with LOCAL_INTERFACE).
<li> A flag to indicate if the object is declared in a C++ file.
<li> The name of the file in which the object was declared.
<li> The complete text of any block comment that preceeds the declarations.
<li> If the declaration occurred inside a preprocessor conditional
     (``#if'') then the text of that conditional is provided.

<li> The complete text of a declaration for the object.
</ul>
The exact output format will not be described here.
It is simple to understand and parse and should be obvious to
anyone who inspects some sample output.
</p>

<a name="H0016"></a>
<h2>5.0 Compiling The Makeheaders Program</h2>

<p>
The source code for makeheaders is a single file of ANSI-C code,
less than 3000 lines in length.
The program makes only modest demands of the system and C library
and should compile without alteration on most ANSI C compilers
and on most operating systems.
It is known to compile using several variations of GCC for Unix
as well as Cygwin32 and MSVC 5.0 for Win32.
</p>

<head><title>The Makeheaders Program</title></head>
<body bgcolor=white>
<h1 align=center>The Makeheaders Program</h1>


<p>
This document describes <em>makeheaders</em>,
a tool that automatically generates &#8220;<code>.h</code>&#8221;
files for a C or C++ programming project.
</p>


<h2>Table Of Contents</h2>

<ul>
................................................................................
<p>
Declarations in C include things such as the following:
<ul>
<li> Typedefs.
<li> Structure, union and enumeration declarations.
<li> Function and procedure prototypes.
<li> Preprocessor macros and #defines.
<li> &#8220;<code>extern</code>&#8221; variable declarations.
</ul>
</p>

<p>
Definitions in C, on the other hand, include these kinds of things:
<ul>
<li> Variable definitions.
................................................................................
modern software engineering.
Another way of looking at the difference is that the declaration
is the <em>interface</em> and the definition is the <em>implementation</em>.
</p>

<p>
In C programs, it has always been the tradition that declarations are
put in files with the &#8220;<code>.h</code>&#8221; suffix and definitions are
placed in &#8220;<code>.c</code>&#8221; files.
The .c files contain &#8220;<code>#include</code>&#8221; preprocessor statements
that cause the contents of .h files to be included as part of the
source code when the .c file is compiled.
In this way, the .h files define the interface to a subsystem and
the .c files define how the subsystem is implemented.
</p>

<a name="H0003"></a>
................................................................................
into the file of your choice.
</p>

<p>
A similar option is -H.  Like the lower-case -h option, big -H
generates a single include file on standard output.  But unlike
small -h, the big -H only emits prototypes and declarations that
have been designated as &#8220;exportable&#8221;.
The idea is that -H will generate an include file that defines
the interface to a library.
More will be said about this in section 3.4.
</p>

<p>
Sometimes you want the base name of the .c file and the .h file to
................................................................................
If you want a particular file to be scanned by makeheaders but you
don't want makeheaders to generate a header file for that file,
then you can supply an empty header filename, like this:
<pre>
   makeheaders alpha.c beta.c gamma.c:
</pre>
In this example, makeheaders will scan the three files named
&#8220;<code>alpha.c</code>&#8221;,
&#8220;<code>beta.c</code>&#8221; and
&#8220;<code>gamma.c</code>&#8221;
but because of the colon on the end of third filename
it will only generate headers for the first two files.
Unfortunately,
it is not possible to get makeheaders to process any file whose
name contains a colon.
</p>

<p>
In a large project, the length of the command line for makeheaders
can become very long.
If the operating system doesn't support long command lines
(example: DOS and Win32) you may not be able to list all of the
input files in the space available.
In that case, you can use the &#8220;<code>-f</code>&#8221; option followed
by the name of a file to cause makeheaders to read command line
options and filename from the file instead of from the command line.
For example, you might prepare a file named &#8220;<code>mkhdr.dat</code>&#8221;
that contains text like this:
<pre>
  src/alpha.c:hdr/alpha.h
  src/beta.c:hdr/beta.h
  src/gamma.c:hdr/gamma.h
  ...
</pre>
................................................................................
Then invoke makeheaders as follows:
<pre>
  makeheaders -f mkhdr.dat
</pre>
</p>

<p>
The &#8220;<code>-local</code>&#8221; option causes makeheaders to
generate of prototypes for &#8220;<code>static</code>&#8221; functions and
procedures.
Such prototypes are normally omitted.
</p>

<p>
Finally, makeheaders also includes a &#8220;<code>-doc</code>&#8221; option.
This command line option prevents makeheaders from generating any
headers at all.
Instead, makeheaders will write to standard output
information about every definition and declaration that it encounters
in its scan of source files.
The information output includes the type of the definition or
declaration and any comment that preceeds the definition or
................................................................................
documentation about the program.
We'll talk more about this feature later.
</p>

<p>
If you forget what command line options are available, or forget
their exact name, you can invoke makeheaders using an unknown
command line option (like &#8220;<code>--help</code>&#8221; or
&#8220;<code>-?</code>&#8221;)
and it will print a summary of the available options on standard
error.
If you need to process a file whose name begins with
&#8220;<code>-</code>&#8221;,
you can prepend a &#8220;<code>./</code>&#8221; to its name in order to get it
accepted by the command line parser.
Or, you can insert the special option &#8220;<code>--</code>&#8221; on the
command line to cause all subsequent command line arguments to be treated as
filenames even if their names begin with &#8220;<code>-</code>&#8221;.
</p>

<a name="H0006"></a>
<h2>3.0 Preparing Source Files For Use With Makeheaders</h2>

<p>
Very little has to be done to prepare source files for use with
................................................................................
This section will describe several typical uses of makeheaders.
</p>

<a name="H0007"></a>
<h3>3.1 The Basic Setup</h3>

<p>
The simplest way to use makeheaders is to put all definitions in
one or more .c files and all structure and type declarations in
separate .h files.
The only restriction is that you should take care to chose basenames
for your .h files that are different from the basenames for your
.c files.
Recall that if your .c file is named (for example)
&#8220;<code>alpha.c</code>&#8221;
makeheaders will attempt to generate a corresponding header file

named &#8220;<code>alpha.h</code>&#8221;.
For that reason, you don't want to use that name for
any of the .h files you write since that will prevent makeheaders
from generating the .h file automatically.
</p>

<p>
The structure of a .c file intented for use with makeheaders is very
simple.
All you have to do is add a single &#8220;<code>#include</code>&#8221; to the
top of the file that sources the header file that makeheaders will generate.
Hence, the beginning of a source file named &#8220;<code>alpha.c</code>&#8221;
might look something like this:
</p>

<pre>
   /*
    * Introductory comment...
    */
................................................................................
   /* The rest of your code... */
</pre>

<p>
Your manually generated header files require no special attention at all.
Code them as you normally would.
However, makeheaders will work better if you omit the
&#8220;<code>#if</code>&#8221; statements people often put around the outside of
header files that prevent the files from being included more than once.
For example, to create a header file named &#8220;<code>beta.h</code>&#8221;,
many people will habitually write the following:

<pre>
   #ifndef BETA_H
   #define BETA_H

   /* declarations for beta.h go here */

................................................................................

You can forego this cleverness with makeheaders.
Remember that the header files you write will never really be
included by any C code.
Instead, makeheaders will scan your header files to extract only
those declarations that are needed by individual .c files and then
copy those declarations to the .h files corresponding to the .c files.
Hence, the &#8220;<code>#if</code>&#8221; wrapper serves no useful purpose.
But it does make makeheaders work harder, forcing it to put
the statements

<pre>
   #if !defined(BETA_H)
   #endif
</pre>
................................................................................
manually written .h files and then automatically generate .h files
corresponding to all .c files.
</p>

<p>
Note that
the wildcard expression used in the above example,
&#8220;<code>*.[ch]</code>&#8221;,
will expand to include all .h files in the current directory, both
those entered manually be the programmer and others generated automatically
by a prior run of makeheaders.
But that is not a problem.
The makeheaders program will recognize and ignore any files it
has previously generated that show up on its input list.
</p>
................................................................................

<ul>
<p><li>
When a function is defined in any .c file, a prototype of that function
is placed in the generated .h file of every .c file that
calls the function.</p>

<P>If the &#8220;<code>static</code>&#8221; keyword of C appears at the
beginning of the function definition, the prototype is suppressed.
If you use the &#8220;<code>LOCAL</code>&#8221; keyword where you would normally
say &#8220;<code>static</code>&#8221;, then a prototype is generated, but it
will only appear in the single header file that corresponds to the
source file containing the function.  For example, if the file
<code>alpha.c</code> contains the following:
<pre>
  LOCAL int testFunc(void){
    return 0;
  }
................................................................................
<pre>
  #define LOCAL static
  LOCAL int testFunc(void);
</pre>
However, no other generated header files will contain a prototype for
<code>testFunc()</code> since the function has only file scope.</p>

<p>When the &#8220;<code>LOCAL</code>&#8221; keyword is used, makeheaders will
also generate a #define for LOCAL, like this:
<pre>
   #define LOCAL static
</pre>
so that the C compiler will know what it means.</p>

<p>If you invoke makeheaders with a &#8220;<code>-local</code>&#8221;
command-line option, then it treats the &#8220;<code>static</code>&#8221;
keyword like &#8220;<code>LOCAL</code>&#8221; and generates prototypes in the
header file that corresponds to the source file containing the function
definition.</p>

<p><li>
When a global variable is defined in a .c file, an
&#8220;<code>extern</code>&#8221;
declaration of that variable is placed in the header of every
.c file that uses the variable.
</p>

<p><li>
When a structure, union or enumeration declaration or a
function prototype or a C++ class declaration appears in a
................................................................................
those files and are not copied.
</p>

<p><li>
When a structure, union or enumeration declaration appears in a .h
file, makeheaders will automatically
generate a typedef that allows the declaration to be referenced without
the &#8220;<code>struct</code>&#8221;, &#8220;<code>union</code>&#8221; or
&#8220;<code>enum</code>&#8221; qualifier.
In other words, if makeheaders sees the code:
<pre>
  struct Examp { /* ... */ };
</pre>
it will automatically generate a corresponding typedef like this:
<pre>
  typedef struct Examp Examp;
................................................................................
The .h files are suppose to contain only interface, not implementation.
C compilers will not enforce this convention, but makeheaders does.
</ul>

<p>
As a final note, we observe that automatically generated declarations
are ordered as required by the ANSI-C programming language.
If the declaration of some structure &#8220;<code>X</code>&#8221; requires a
prior declaration of another structure &#8220;<code>Y</code>&#8221;, then Y will
appear first in the generated headers.
</p>

<a name="H0009"></a>
<h3>3.3 How To Avoid Having To Write Any Header Files</h3>

<p>
In my experience, large projects work better if all of the manually
................................................................................
You can instruct makeheaders to treat any part of a .c file as if
it were a .h file by enclosing that part of the .c file within:
<pre>
   #if INTERFACE
   #endif
</pre>
Thus any structure definitions that appear after the
&#8220;<code>#if INTERFACE</code>&#8221; but before the corresponding
&#8220;<code>#endif</code>&#8221; are eligable to be copied into the
automatically generated
.h files of other .c files.
</p>

<p>
If you use the &#8220;<code>#if INTERFACE</code>&#8221; mechanism in a .c file,
then the generated header for that .c file will contain a line
like this:
<pre>
   #define INTERFACE 0
</pre>
In other words, the C compiler will never see any of the text that
defines the interface.
................................................................................
putting the declarations in the correct ANSI-C order -- makeheaders
will do that for you automatically.
</p>

<p>
Note that you don't have to use this approach exclusively.
You can put some declarations in .h files and others within the
&#8220;<code>#if INTERFACE</code>&#8221; regions of .c files.
Makeheaders treats all declarations alike, no matter where they
come from.
You should also note that a single .c file can contain as many
&#8220;<code>#if INTERFACE</code>&#8221; regions as desired.
</p>

<a name="H0010"></a>
<h3>3.4 Designating Declarations For Export</h3>

<p>
In a large project, one will often construct a hierarchy of
................................................................................
(The second interface is normally a subset of the first.)
Ordinary C does not provide support for a tiered interface
like this, but makeheaders does.
</p>

<p>
Using makeheaders, it is possible to designate routines and data
structures as being for &#8220;<code>export</code>&#8221;.
Exported objects are visible not only to other files within the
same library or subassembly but also to other
libraries and subassemblies in the larger program.
By default, makeheaders only makes objects visible to other members
of the same library.
</p>

................................................................................
This is not a perfect solution, but it works well in practice.
</p>

<p>
But trouble quickly arises when we attempt to devise a mechanism for
telling makeheaders which prototypes it should export and which it should
keep local.
The built-in &#8220;<code>static</code>&#8221; keyword of C works well for
prohibiting prototypes from leaving a single source file, but because C doesn't
support a linkage hierarchy, there is nothing in the C language to help us.
We'll have to invite our own keyword: &#8220;<code>EXPORT</code>&#8221;
</p>

<p>
Makeheaders allows the EXPORT keyword to precede any function or
procedure definition.
The routine following the EXPORT keyword is then eligable to appear
in the header file generated using the -H command line option.
................................................................................
are visible to all files within the library, any declarations
or definitions within
<pre>
   #if EXPORT_INTERFACE
   #endif
</pre>
will become part of the exported interface.
The &#8220;<code>#if EXPORT_INTERFACE</code>&#8221; mechanism can be used in
either .c or .h files.
(The &#8220;<code>#if INTERFACE</code>&#8221; can also be used in both .h and
.c files, but since it's use in a .h file would be redundant, we haven't
mentioned it before.)
</p>

<a name="H0011"></a>
<h3>3.5 Local declarations processed by makeheaders</h3>

<p>
Structure declarations and typedefs that appear in .c files are normally
ignored by makeheaders.
Such declarations are only intended for use by the source file in which
they appear and so makeheaders doesn't need to copy them into any
generated header files.
We call such declarations &#8220;<code>private</code>&#8221;.
</p>

<p>
Sometimes it is convenient to have makeheaders sort a sequence
of private declarations into the correct order for us automatically.
Or, we could have static functions and procedures for which we would like
makeheaders to generate prototypes, but the arguments to these
................................................................................
<p>
When this situation arises, enclose the private declarations
within
<pre>
  #if LOCAL_INTERFACE
  #endif
</pre>
A &#8220;<code>LOCAL_INTERFACE</code>&#8221; block works very much like the
&#8220;<code>INTERFACE</code>&#8221; and
&#8220;<code>EXPORT_INTERFACE</code>&#8221;
blocks described above, except that makeheaders insures that the
objects declared in a LOCAL_INTERFACE are only visible to the
file containing the LOCAL_INTERFACE.
</p>

<a name="H0012"></a>
<h3>3.6 Using Makeheaders With C++ Code</h3>

<p>
You can use makeheaders to generate header files for C++ code, in
addition to C.
Makeheaders will recognize and copy both &#8220;<code>class</code>&#8221;
declarations
and inline function definitions, and it knows not to try to generate
prototypes for methods.
</p>

<p>
In fact, makeheaders is smart enough to be used in projects that employ
a mixture of C and C++.
................................................................................
<p>
No special command-line options are required to use makeheaders with
C++ input.  Makeheaders will recognize that its source code is C++
by the suffix on the source code filename.  Simple ".c" or ".h" suffixes
are assumed to be ANSI-C.  Anything else, including ".cc", ".C" and
".cpp" is assumed to be C++.
The name of the header file generated by makeheaders is derived from
the name of the source file by converting every "c" to "h" and
every "C" to "H" in the suffix of the filename.
Thus the C++ source
file &#8220;<code>alpha.cpp</code>&#8221; will induce makeheaders to
generate a header file named &#8220;<code>alpha.hpp</code>&#8221;.
</p>

<p>
Makeheaders augments class definitions by inserting prototypes to
methods where appropriate.  If a method definition begins with one
of the special keywords <b>PUBLIC</b>, <b>PROTECTED</b>, or
<b>PRIVATE</b> (in upper-case to distinguish them from the regular
C++ keywords with the same meaning) then a prototype for that
method will be inserted into the class definition.  If none of
these keywords appear, then the prototype is not inserted.  For
example, in the following code, the constructor is not explicitly
declared in the class definition but makeheaders will add it there
................................................................................
</p>

<h4>3.6.1 C++ Limitations</h4>

<p>
Makeheaders does not understand more recent
C++ syntax such as templates and namespaces.
Perhaps these issues will be addressed in future revisions.
</p>

<a name="H0013"></a>
<h3>3.7 Conditional Compilation</h3>

<p>
The makeheaders program understands and tracks the conditional
compilation constructs in the source code files it scans.
Hence, if the following code appears in a source file
<pre>
  #ifdef UNIX
  #  define WORKS_WELL 1
  #else
  #  define WORKS_WELL 0
  #endif
</pre>
then the next patch of code will appear in the generated header for
every .c file that uses the WORKS_WELL constant:
<pre>
  #if defined(UNIX)
  #  define WORKS_WELL 1
................................................................................
</p>

<p>
Makeheaders does not understand the old K&amp;R style of function
and procedure definitions.
It only understands the modern ANSI-C style, and will probably
become very confused if it encounters an old K&amp;R function.
Therefore you should take care to avoid putting K&amp;R function definitions
in your code.
</p>

<p>
Makeheaders does not understand when you define more than one
global variable with the same type separated by a comma.
In other words, makeheaders does not understand this:
<pre>
................................................................................
     unrelated file in a different part of the source tree.
<li> Information is kept in only one place.  When a change occurs
     in the code, it is not necessary to make a corresponding change
     in a separate document.  Just rerun the documentation generator.
</ul>
The makeheaders program does not generate program documentation itself.
But you can use makeheaders to parse the program source code, extract
the information that is relevant to the documentation and to pass this
information to another tool to do the actual documentation preparation.
</p>

<p>
When makeheaders is run with the &#8220;<code>-doc</code>&#8221; option, it
emits no header files at all.
Instead, it does a complete dump of its internal tables to standard
output in a form that is easily parsed.
This output can then be used by another program (the implementation
of which is left as an exercise to the reader) that will use the
information to prepare suitable documentation.
</p>

<p>
The &#8220;<code>-doc</code>&#8221; option causes makeheaders to print
information to standard output about all of the following objects:
<ul>
<li> C++ class declarations
<li> Structure and union declarations
<li> Enumerations
<li> Typedefs
<li> Procedure and function definitions
<li> Global variables
<li> Preprocessor macros (ex: &#8220;<code>#define</code>&#8221;)
</ul>
For each of these objects, the following information is output:
<ul>
<li> The name of the object.
<li> The type of the object.  (Structure, typedef, macro, etc.)
<li> Flags to indicate if the declaration is exported (contained within
     an EXPORT_INTERFACE block) or local (contained with LOCAL_INTERFACE).
<li> A flag to indicate if the object is declared in a C++ file.
<li> The name of the file in which the object was declared.
<li> The complete text of any block comment that preceeds the declarations.
<li> If the declaration occurred inside a preprocessor conditional
     (&#8220;<code>#if</code>&#8221;) then the text of that conditional is
     provided.
<li> The complete text of a declaration for the object.
</ul>
The exact output format will not be described here.
It is simple to understand and parse and should be obvious to
anyone who inspects some sample output.
</p>

<a name="H0016"></a>
<h2>5.0 Compiling The Makeheaders Program</h2>

<p>
The source code for makeheaders is a single file of ANSI-C code,
approximately 3000 lines in length.
The program makes only modest demands of the system and C library
and should compile without alteration on most ANSI C compilers
and on most operating systems.
It is known to compile using several variations of GCC for Unix
as well as Cygwin32 and MSVC 5.0 for Win32.
</p>