The cross reference listing is written to the standard output stram.
The program oxref generates a cross reference listing of symbols defined in non-stripped object files and/or libraries.
A cross reference listing shows the functions using certain symbols (functions, data). This is useful information during program development and debugging phases. E.g., assuming that the signature; the pre-conditions or the post-conditions of a function must be changed it is important to know from what function(s) the function-to-modify is called to verify that the changes to the modified function do not break its calling functions.
The generated cross reference listing starts with a header showing information about the program, a time stamp and the arguments passed to oxref. E.g.,
oxref by Frank B. Brokken (f.b.brokken@rug.nl) oxref V0.90.00 2011 CREATED Wed, 16 Feb 2011 15:21:03 +0000 CROSS REFERENCE FOR: --select define liboxref.a ----------------------------------------------------------------------
Oxref returns 0 to the operating system unless an error occurs or oxref's version or usage info is shown or requested. In those cases 1 is returned
If available, single letter options are listed between parentheses following their associated long-option variants. Single letter options require arguments if their associated long options require arguments as well.
count - function parameters are suppressed; instead the number of arguments required by a function is shown in its parameter list. Example:
usage(1)
instead of
usage(std::string const&)
first - only show the first word of parameters. Example:
insertDefined(unsigned, std::ostream&, std::vector&)
instead of
insertDefined(unsigned int, std::ostream&, std::vector<XrefData,
std::allocator<XrefData> > const&)
<len> - where <len> is a positive integral number (5 is used if <len> is less than 5). <len> specifies the maximum length of parameter names. If parameter names need to be truncated, an ellipsis replaces the truncated characters. Example using -a 12:
insertDefined(unsigned int, std::ostream&, std::vect...&)
instead of
insertDefined(unsigned int, std::ostream&, std::vector<XrefData,
std::allocator<XrefData> > const&)
insertDefined(unsigned int, std::ostream&, std::vector<XrefData,
std::allocator<XrefData> > const&)
Full name: Store::insertDefined(unsigned int, std::ostream&,
std::vector<XrefData, std::allocator<XrefData> > const&)
The examples show how oxref was called, followed by a representative example of a cross-reference listing for a symbol. Oxref's own cross reference listing was used:
called as: oxref liboxref
define(std::string const&, bool)
Used By:
Store::setFunction(std::string const&)
Store::setObject(std::string const&)
Store::setSource(std::string const&)
--------------------
called as: oxref -foxs liboxref
define(std::string const&, bool)
Full name: Store::define(std::string const&, bool)
Source: define.cc (1define.o)
Used By:
setfunction.cc: Store::setFunction(std::string const&)
setobject.cc: Store::setObject(std::string const&)
setsource.cc: Store::setSource(std::string const&)
This is the initial release version of oxref.
In theory, creating cross reference listings is a complex matter as it requires a full syntax analysis of the sources defining a program. Especially with complex languages like C++ this is a difficult hurdle to pass.
Looking for `cross reference programs' using a search engine returns remarkably few hits. LXR is a promising cross referencing program (see http://lxr.linux.no/), but it requires the use of data base packages, making it somewhat complex to use. Other links refer to cross-reference programs for textual documents, not programs.
The complexity of developing a program generating a cross reference listing has baffled me for a long time. Eventually I realized that in practice the essential information has already been generated by the compiler, when it compiles our source files. So why do it all again?
Once a program has been compiled one or (usually) more object files are available. The linker uses tables of defined and external symbols embedded in the object files to connect the various functions. If all requirements can be satisfied the linker is able to create a running program.
Programs like nm(1) and objdump(1) can be used to produce human readable output from the information embedded in object files. Oxref reads this information and organizes it, creating a cross reference listing.
Since all compilable program languages generate identically organized object files (or maybe better: generate object files that can be interpreted by objdump(1)), oxref can broadly be applied. As long as objdump(1) produces sensible output oxref should be able to generate a cross reference listing.
Oxref's name consists of two syllables: o and xref. The o represents the program objdump(1), called from oxref as a child program. The important part is of course the cross-referencing of symbols. Like the common abbreviation of rail-road crossing, rail-road xing, cross referencing is abbreviated to xref. Hence oxref.
Of course, nearly everybody will read oxref as ox-ref. Fortunately, here too we're on familiar ground: Bison, Cow, Gnu, Yacc: all are bovine animals. To that important list oxref adds the Ox.
An example of oxref's own cross reference listing is provided (on Debian systems) in the file
/usr/share/doc/oxref/oxref.xref.gz
nm(1), objdump(1), pattern(3bobcat), regex(7)
Frank B. Brokken (f.b.brokken@rug.nl).