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  10 <h1>CXREF VERSION 1.5 - FREQUENTLY ASKED QUESTIONS AND ANSWERS</h1>
  11
  12 This file contains a list of frequently asked questions and their answers
  13 relating to cxref version 1.5.
  14
  15 Not all of the questions here are real users questions, some of them have been
  16 made up to give some help to people trying to use the program who find that the
  17 README documentation is insufficient.
  18 <hr>
  19 <p><b><a href="#Section-0">Section 0 - Why doesn't this FAQ answer my question?</a></b>
  20 <p><b><a href="#Section-1">Section 1 - What does cxref do (and what it doesn't)</a></b>
  21 <p><a href="#Q-1.1">Q 1.1   Does cxref support C++?</a>
  22 <p><a href="#Q-1.2">Q 1.2   Does cxref show which #includes that are not needed?</a>
  23 <p><a href="#Q-1.3">Q 1.3   Can cxref document automatic function variables?</a>
  24 <p><a href="#Q-1.4">Q 1.4   Does cxref run on systems other than UNIX?</a>
  25 <p><b><a href="#Section-2">Section 2 - When cxref does not work</a></b>
  26 <p><a href="#Q-2.1a">Q 2.1a  How do I find out what is causing the parse error?</a>
  27 <p><a href="#Q-2.1b">Q 2.1b  What does this parse error message mean?</a>
  28 <p><a href="#Q-2.2">Q 2.2   Where are files doc/cxref.html &amp; FAQ.html referenced from README.html?</a>
  29 <p><a href="#Q-2.3">Q 2.3   Why are half of the cross references missing?</a>
  30 <p><a href="#Q-2.4">Q 2.4   Why can't cxref process my header file in isolation?</a>
  31 <p><a href="#Q-2.5">Q 2.5   Why can't LaTeX process the output files?</a>
  32 <p><a href="#Q-2.6">Q 2.6   Why does the include file name have the complete path name?</a>
  33 <p><a href="#Q-2.7">Q 2.7   Why does the include file name have the wrong path name?</a>
  34 <p><a href="#Q-2.8">Q 2.8   Why does cxref put in links to system include files?</a>
  35 <p><b><a href="#Section-3">Section 3 - How to make cxref do what you want</a></b>
  36 <p><a href="#Q-3.1">Q 3.1   How do I use cxref to process source files in more than one directory?</a>
  37 <p><a href="#Q-3.2">Q 3.2   How can I add my own information to the output files?</a>
  38 <p><a href="#Q-3.3">Q 3.3   Can I get a subset of the cross-reference information?</a>
  39 <p><a href="#Q-3.4">Q 3.4   Is there an easy way to generate the comments in the correct format?</a>
  40 <p><a href="#Q-3.5">Q 3.5   How do I produce LaTeX output from a single source.c.tex output file?</a>
  41 <p><a href="#Q-3.6">Q 3.6   How can I pass extra arguments to the C pre-processor?</a>
  42 <p><a href="#Q-3.7">Q 3.7   Can I cross-reference my source code at the same time as compiling it?</a>
  43 <p><a href="#Q-3.8">Q 3.8   What use is the .cxref configuration file?</a>
  44 <p><b><a href="#Section-4">Section 4 - More information about cxref</a></b>
  45 <p><a href="#Q-4.1">Q 4.1   Who wrote cxref, When and Why?</a>
  46 <p><a href="#Q-4.2">Q 4.2   How do I report bugs in cxref?</a>
  47 <hr>
  48 <h2><a name="Section-0">Section 0 - Why doesn't this FAQ answer my question?</a></h2>
  49
  50 This FAQ is released with each new version of the cxref program, so if the
  51 question is one that is frequently asked about the new version then you will by
  52 definition not find the answer here.
  53
  54 You can find the latest information about cxref at the cxref web-page, this
  55 contains among other things a list of bug-fixes for the latest version.
  56 <a href="http://www.gedanken.demon.co.uk/cxref/">http://www.gedanken.demon.co.uk/cxref/</a>
  57 <hr>
  58 <h2><a name="Section-1">Section 1 - What does cxref do (and what it doesn't)</a></h2>
  59 <h3><a name="Q-1.1">Q 1.1   Does cxref support C++?</a></h3>
  60 <pre>
  61 No.
  62
  63 The cxref program only works for C, More specifically:
  64
  65 1) ANSI standard C with some leniency for common non-ANSI syntax.
  66         For example, the construct 'switch(foo) { case 1: ... default: }' is not
  67         ANSI, there must be a ';' after the default label, but it is accepted by
  68         cxref.
  69
  70 2) Traditional (K&amp;R) function declarations, with implicit 'int' and 'void'.
  71         For example 'foo(){}' is parsed as if 'int foo(void){}' was specified.
  72
  73 3) The ability to parse GCC extensions.
  74         The GCC '__attribute__' and '__extension__' keywords and most of the
  75         other GCC extensions. The 'inline' keyword is allowed.
  76 </pre>
  77 <h3><a name="Q-1.2">Q 1.2   Does cxref show which #includes that are not needed?</a></h3>
  78 <pre>
  79 No.
  80
  81 The output of the cxref program cross-references all of the functions,
  82 variables, type definitions, included file etc.  There is not a way of
  83 identifying files that are included in another source file that do not need to
  84 be.
  85 </pre>
  86 <h3><a name="Q-1.3">Q 1.3   Can cxref document automatic function variables?</a></h3>
  87 <pre>
  88 No.
  89
  90 The inclusion of automatic variables in the output is not included.  This is
  91 because of the number of them in a typical function.  In theory it could be made
  92 to do this.
  93 </pre>
  94 <h3><a name="Q-1.4">Q 1.4   Does cxref run on systems other than UNIX?</a></h3>
  95 <pre>
  96 For example DOS / Win3 / Win95 / WinNT / OS/2.
  97
  98 UNIX    = Yes
  99         This is the system that the program way designed and initially written
 100         for, it should work on many versions of UNIX.
 101         I know that it works on Linux, SunOS 4.1.x, Solaris 2.x, AIX &amp; HP-UX 10.
 102
 103 DOS/Win3 = No
 104         The program was not designed for DOS, the filenames used and the
 105         multi-process nature of the program do not allow this.
 106
 107 Win95/WinNT = Yes
 108         Using the Cygwin library and tools <a href="http://sourceware.cygnus.com/cygwin/">http://sourceware.cygnus.com/cygwin/</a>
 109         it is possible to compile and run the programs.
 110
 111 OS/2    = Maybe
 112         I have reports that it is possible with OS/2 Warp with emx, but I do not
 113         support cxref for this OS.
 114 </pre>
 115 <hr>
 116 <h2><a name="Section-2">Section 2 - When cxref does not work</a></h2>
 117 <h3><a name="Q-2.1a">Q 2.1a  How do I find out what is causing the parse error?</a></h3>
 118 <pre>
 119 The following error message is generated by cxref when parsing a source file
 120 (with YYDEBUG set to 0 in parse-yy.h when cxref was compiled).
 121
 122 test.c:   4: parse error, expecting `','' or `';''
 123 ^^^^^^  ^^^  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 124 file    line            type of error
 125 name    number        generated by yacc
 126
 127 The error is on line 4 of the file test.c.  In this case, the error message that
 128 the yacc parser is generating is of some help, more often the error message is
 129 just 'parse error'.
 130
 131 If YYDEBUG was set to 1 in parse-yy.h, then a more detailed error message would
 132 be given (<a href="#Q-2.1b">See Q 2.1b</a>).
 133 </pre>
 134 <h3><a name="Q-2.1b">Q 2.1b  What does this parse error message mean?</a></h3>
 135 <pre>
 136 The following error message is generated by cxref when parsing a source file
 137 (with YYDEBUG set to 1 in parse-yy.h when cxref was compiled).
 138
 139 test.c:   4: parse error, expecting `','' or `';''
 140
 141 The previous 10, current and next 10 symbols are:
 142  -8 | 296 :              INT : int
 143  -7 | 258 :       IDENTIFIER : foo
 144  -6 |  40 :                  : (
 145  -5 | 292 :             VOID : void
 146  -4 |  41 :                  : )
 147  -3 | 123 :                  : {
 148  -2 | 296 :              INT : int
 149  -1 | 258 :       IDENTIFIER : a
 150   0 | 296 :              INT : int
 151   1 | 258 :       IDENTIFIER : b
 152   2 |  59 :                  : ;
 153   3 | 125 :                  : }
 154 END OF FILE
 155 ^^^               ^^^^^^^^^^  ^^^^^
 156 symbol              symbol    symbol
 157 number               type     value
 158
 159 From this we can reconstruct part of the file test.c, using the previous and
 160 next 10 symbol values from the lexer.
 161
 162 int foo(void) { int a   int b; }
 163                       ^
 164 This is where the parse error occurred, after 'int a' and before 'int b;'.
 165 The cause of the error is now clear, there is a ';' missing after the
 166 declaration of the variable a.
 167
 168 The cxref program is intended to be used on source files that are known to
 169 compile with a C compiler.  In this case a parse error message should not be
 170 seen except for either non-standard C, (and compiler) or a bug in cxref.
 171 </pre>
 172 <h3><a name="Q-2.2">Q 2.2   Where are files doc/cxref.html &amp; FAQ.html referenced from README.html?</a></h3>
 173 <pre>
 174 The README.html file has a reference to the files doc/cxref.html and FAQ.html
 175 these files are only present when 'make docs' has been run to generate the cross
 176 references for the cxref program itself.
 177 </pre>
 178 <h3><a name="Q-2.3">Q 2.3   Why are half of the cross references missing?</a></h3>
 179 <pre>
 180 The way that cxref works is that it processes all of the source files for a
 181 program, one at a time and generates a cross reference database.  A second pass
 182 of the program is required to generate all of the cross references from the
 183 database of cross reference information.
 184
 185 For this reason, the Makefile for the doc directory of cxref uses 'cxref *.c
 186 -xref -Odoc' for the first pass and 'cxref *.c -xref -Odoc -html -latex' for the
 187 second pass.  The first to build the database, the second to produce the
 188 outputs.
 189
 190 The reason that the cross references are missing is that only one pass of the
 191 program has been done on all of the files.  The later files to be be processed
 192 will have cross references for the earlier files processed.
 193 </pre>
 194 <h3><a name="Q-2.4">Q 2.4   Why can't cxref process my header file in isolation?</a></h3>
 195 <pre>
 196 The cxref program needs to process the header files to enable a cross reference
 197 for them to be generated.  In many cases, the header file will not have been
 198 written with this in mind, and may rely on other header files being included
 199 before the one being processed.  The best solution to this is to modify the
 200 header file so that it includes all of the header files that it needs.
 201
 202 Another option is to use '-- -include filename.h' on the command line.  This
 203 will include the specified file (filename.h) into the source file that is being
 204 processed at the beginning.
 205
 206 There is a Perl script supplied with the cxref source files called fixheader.
 207 This can be used to automatically determine what header files may be required.
 208 The decision is based on the header files that are used for the files that cxref
 209 can process and lots of test compilations.
 210 </pre>
 211 <h3><a name="Q-2.5">Q 2.5   Why can't LaTeX process the output files?</a></h3>
 212 <pre>
 213 There are two options for producing LaTeX output, '-latex' and '-latex2e'.
 214 These refer to two different versions of the LaTeX program.  The first is for
 215 use with LaTeX version 2.0.9, the second for use with LaTeX version 2e.
 216
 217 The file cxref.tex (or basename.tex if '-Nbasename' is used) is the file that
 218 must be processed by LaTeX.
 219 </pre>
 220 <h3><a name="Q-2.6">Q 2.6   Why does the include file name have the complete path name?</a></h3>
 221 <pre>
 222 This is because a standard C preprocessor is being used instead of cxref-cpp or
 223 an appropriate version of gcc.  One of the changes to the recent versions of gcc
 224 (2.8.0) has been made to the GNU cccp to make cxref-cpp.  This is to make it
 225 output the names of the include files as they are in the original source code
 226 and not after the files have been translated into an absolute pathname.
 227 </pre>
 228 <h3><a name="Q-2.7">Q 2.7   Why does the include file name have the wrong path name?</a></h3>
 229 <pre>
 230 If the answer to this question is not the same as the answer to Q 2.6 then it
 231 could be the following.  When the files that are being cross-referenced are in a
 232 directory that contains a symbolic link in the path then the current directory
 233 has two (or more) possible names.  The way that the cxref program works is that
 234 it finds the current working directory (which is the real pathname, not using
 235 any links).  If the name that you specify using -R is another name for the same
 236 directory then cxref will not realise that they are the same.  This can cause
 237 the pathnames to become confused.  Try using relative pathnames where possible
 238 for the -R and -I options.
 239 </pre>
 240 <h3><a name="Q-2.8">Q 2.8   Why does cxref put in links to system include files?</a></h3>
 241 <pre>
 242 The way that cxref knows which include files are local to the program and which
 243 ones are system ones is by the way that they are included.  Any that use double
 244 quotes '"' are local ones and wil have links to them included in the cross
 245 reference output.  The include files that use the angle brackets '&lt;&gt;' are system
 246 files and do not have links to them included.
 247
 248 The best solution is to change the include files so that the distinction is
 249 clear.  An alternative is to use the '-isystem DIRNAME' option of gcc.  This
 250 will cause gcc to treat files in this directory as if they are system files.
 251 Since cxref uses gcc for the pre-processing, this option can be passed through
 252 using 'cxref file.c -- -isystem DIRNAME'.
 253 </pre>
 254 <hr>
 255 <h2><a name="Section-3">Section 3 - How to make cxref do what you want</a></h2>
 256 <h3><a name="Q-3.1">Q 3.1   How do I use cxref to process source files in more than one directory?</a></h3>
 257 <pre>
 258 The cxref program depends on a database of cross references, these must all be
 259 consistent.  This requires that all of the files to be cross referenced are in
 260 the same directory tree.
 261
 262 Example:
 263
 264 directory     files
 265 - - - - -     - - -
 266 basedir    :  f0.c f0.h ...
 267  |- s1     :  f1.c f1.h ...
 268  |- s2     :  f2.c f2.h ...
 269 ...
 270
 271 -- f2.c --
 272 #include &lt;...&gt;
 273 #include "f2.h"
 274 #include "../s1/f1.h"
 275 #include "f0.h"
 276 ----------
 277
 278 In the base directory 'basedir' run 'cxref -xref -Odoc s2/f2.c -html -I.'.  This
 279 will create the file 'doc/s2/f2.c.html' for the file 'f2.c' and this will
 280 contain references to the files 'doc/s2/f2.h.html', 'doc/s1/f1.h.html' and
 281 'doc/f0.h.html'.  The subdirectories 'doc/s1', 'doc/s2' will be automatically
 282 created within the 'doc' directory to put the files into (the 'doc' directory
 283 must already exist).
 284
 285 directory        files
 286 - - - - -        - - -
 287 basedir
 288  |- doc       :  f0.c.html f0.h.html ... cxref.html
 289      |- s1    :  f1.c.html f1.h.html ...
 290      |- s2    :  f2.c.html f2.h.html ...
 291 ...
 292
 293 An alternative method is to use the -R option to cxref.  In the directory 's2',
 294 cxref can be run as 'cxref -R.. -xref -Odoc f2.c -html -I.'.  This will change
 295 directory to '..' ('basedir') before cxref is run, and will modify the cxref
 296 arguments so that it is equivalent to running cxref from 'basedir' as detailed
 297 above.
 298 </pre>
 299 <h3><a name="Q-3.2">Q 3.2   How can I add my own information to the output files?</a></h3>
 300 <pre>
 301 The files cxref.html and cxref.tex (depending on whether using HTML or LaTeX
 302 format and the use of the '-Nbasename' option) are the ones to edit.  These
 303 files contain the lines 'Begin-Of-Source-Files' and 'End-Of-Source-Files' as
 304 comments.  The output files for each source file are automatically included
 305 between these lines if they do not already exist there.  The order of these
 306 files and any other text between these lines is not important.  Customisation of
 307 the files should be added here.  The output files for each source file are
 308 automatically generated so any edits made to these will be lost when cxref is
 309 run.
 310 </pre>
 311 <h3><a name="Q-3.3">Q 3.3   Can I get a subset of the cross-reference information?</a></h3>
 312 <pre>
 313 At the moment, the only one way to limit the amount of cross referencing is to
 314 use the '-xref-*' command line option (see README).  There are plans for a
 315 future version of cxref to have an options file that would allow different
 316 amounts of information to be generated in the output.  For example, only to
 317 display called and not calls information for each function.
 318 </pre>
 319 <h3><a name="Q-3.4">Q 3.4   Is there an easy way to generate the comments in the correct format?</a></h3>
 320 <pre>
 321 The only easy way to do this is to use the cxref.el macro file and Emacs.  This
 322 is what is used to generate the comments in the cxref source code itself.
 323 </pre>
 324 <h3><a name="Q-3.5">Q 3.5   How do I produce LaTeX output from a single source.c.tex output file?</a></h3>
 325 <pre>
 326 The file cxref.tex (or basename.tex if '-Nbasename' is used) is the file that
 327 must be processed by LaTeX.  All of the individual LaTeX files for the source
 328 files are included into this file.  If an individual file source.c.tex needs to
 329 be processed then a copy of the file cxref.tex should be modified to include
 330 only the required source.c.tex file.
 331 </pre>
 332 <h3><a name="Q-3.6">Q 3.6   How can I pass extra arguments to the C pre-processor?</a></h3>
 333 <pre>
 334 The cxref program itself has three ways that you can specify the arguments that
 335 are passed to the C pre-processor.
 336
 337 a) The -CPP option allows the name of the pre-processor program itself to be
 338    changed.
 339    e.g. 'cxref -CPP "/usr/foo/cpp -C" foo.c' will use the cpp from /usr/foo
 340    instead of the compiled in default and pass it the option -C.
 341
 342 b) The most common C pre-processor commands are recognised by cxref
 343    automatically, these are -D*, -U* and -I*.
 344
 345 c) Any amount of extra options can be passed to the preprocessor by appending
 346    them to the command line after the end-of-arguments marker '--'.
 347    e.g. 'cxref foo.c -- -traditional' will pass -traditional to the
 348    pre-processor.
 349 </pre>
 350 <h3><a name="Q-3.7">Q 3.7   Can I cross-reference my source code at the same time as compiling it?</a></h3>
 351 <pre>
 352 It is possible to cross-reference and document your source code at the same time
 353 as compiling it by using the cxref-cc script.  This takes the same arguments as
 354 your usual C compiler and performs both functions.
 355
 356 First it calls the C compiler and passes on all of the command line arguments.
 357 The real C compiler is specified by the CXREFCC environment variable, or the CC
 358 environment variable or it will use gcc if neither of these are set.
 359
 360 Second the arguments that cxref needs to have are extracted from the arguments
 361 that the C compiler had and cxref is called.  The arguments that are kept are
 362 the -D*, -U*, -I* arguments to specify #defines and #include paths, and the file
 363 name of the source file itself.  Any other arguments are taken from the .cxref
 364 file (<a href="#Q-3.8">See Q 3.8</a>).
 365
 366 After doing this it will still be necessary to sort out the header files since
 367 these are not cross-referenced using this method.
 368 </pre>
 369 <h3><a name="Q-3.8">Q 3.8   What use is the .cxref configuration file?</a></h3>
 370 <pre>
 371 The most obvious use is if you have a lot of command line options that you don't
 372 want to have to enter every time that you run the program.
 373
 374 However the .cxref file is most useful when you have a multiple directory source
 375 tree (See&lt; Q 3.1), or when you are using an existing Makefile to build
 376 documentation.
 377
 378 When there are various subdirectories containing source code, a .cxref file in
 379 each sub-directory can be used just containing the line '-R..' or whatever is
 380 appropriate to point cxref to the root of the source tree.  This means that
 381 there is no need to keep track of which directory you are in, they all will use
 382 the correct directory to work from.
 383
 384 If you already have a Makefile that goes through all of the source code then you
 385 may want to modify it so that it calls cxref instead of calling the C compiler.
 386 This means that there is no room to put the extra arguments to cxref on the
 387 command line.  A .cxref file can contain the command line arguments so that you
 388 only need to need the arguments that are already there for the C compiler
 389 (<a href="#Q-3.7">See Q 3.7</a>).
 390 </pre>
 391 <hr>
 392 <h2><a name="Section-4">Section 4 - More information about cxref</a></h2>
 393 <h3><a name="Q-4.1">Q 4.1   Who wrote cxref, When and Why?</a></h3>
 394 <pre>
 395 The cxref program was written by Andrew M. Bishop (amb@gedanken.demon.co.uk) in
 396 1995,96,97,98,99 and maintained since then.
 397
 398 There is a cxref home-page on the World Wide Web, available via the author's
 399 home-page at <a href="http://www.gedanken.demon.co.uk/">http://www.gedanken.demon.co.uk/</a> .  This is kept updated with news
 400 about the program, as new versions become available.
 401
 402 An earlier program by the same author using basically the same comment
 403 convention was written in Emacs Lisp in 1994.  This version was slow, the amount
 404 of cross referencing was poor and the output was only in troff format.  The
 405 current C program was written to replace this but has grown to become much
 406 better in the cross referencing that is done and the format of the output has
 407 increased greatly.
 408
 409 The cxref program can be freely distributed according to the terms of the GNU
 410 General Public License (see the file `COPYING').
 411 </pre>
 412 <h3><a name="Q-4.2">Q 4.2   How do I report bugs in cxref?</a></h3>
 413 <pre>
 414 By e-mail, send them to me at amb@gedanken.demon.co.uk and put cxref somewhere
 415 in the subject line.  You can also report bugs or provide comments via the
 416 feedback form on the cxref home-page on the World Wide Web accessible via
 417 <a href="http://www.gedanken.demon.co.uk/">http://www.gedanken.demon.co.uk/</a> .
 418
 419 Before doing this, you should check the FAQ and the cxref web-page to see if the
 420 answer is there.  If it is not, and it is a parse error then check that it is a
 421 cxref problem and not a syntax error in the source file.
 422 When you are sure that it is a cxref bug, give me as much information as you
 423 can, about the error, when it happens, what system you are using etc.  It is
 424 useful if you can provide a small example and the output of using the '-raw'
 425 option to provide the actual output that you are seeing.  (If it is an HTML or
 426 LaTeX specific problem then send that file instead.)
 427 </pre>
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