Merge branch 'topic/sync-to-go-2'

[s-roff.git] / man / tmac-trace.7.in

.ig
@L_ROFF@_trace.7

Copyright (c) 2014 - 2017 Steffen (Daode) Nurpmeso <steffen@sdaoden.eu>.

Copyright (C) 2002, 2006 - 2008 Free Software Foundation, Inc.
written by Bernd Warken.

Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.1 or
any later version published by the Free Software Foundation; with the
Invariant Sections being this .ig-section and AUTHOR, with no
Front-Cover Texts, and with no Back-Cover Texts.

You should have received a copy of the Free Documentation License
as part of the file COPYING; also located in the main directory of the
source package of this program.
..
.
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.
.TH @U_ROFF@_TRACE @MAN7EXT@ "@MDATE@" "@T_ROFF@ v@VERSION@"
.
.\"
.SH NAME
@L_ROFF@_trace \- @T_ROFF@ macro package trace.tmac
.
.\"
.SH SYNOPSIS
.
.SY "@L_ROFF@ \-m trace"
.RI [ options
.IR \*[Ellipsis] ]
.RI [ files
.IR \*[Ellipsis] ]
.YS
.
.\"
.SH DESCRIPTION
.
The
.I trace
macro package can be a valuable tool for debugging documents written
in the roff formatting language.
A call stack trace is protocolled on standard error, this is, a
diagnostic message is emitted on entering and exiting of a macro call.
This greatly eases to track down an error in some macro.
.
.P
This tracing process is activated by specifying the groff or troff
command line option
.BR \-m\ trace .
A finer control can be obtained by including the macro file within the
document via
.BR .mso\ trace.tmac .
Only macros that are defined after this line are traced.
.
.P
If command line option
.B \-r\ trace-full=1
is given (or if this register is set in the document), number and string
register assignments together with some other requests are traced also.
.
.P
If some other macro package should be traced as well it must be specified
after
.B \-m\ trace
on the command line.
.
.P
The macro file
.B trace.tmac
is unusual because it does not contain any macros to be called by a
user.
Instead, the existing macro definition and appending facilities are
modified such that they display diagnostic messages.
.
.\"
.SH EXAMPLES
.
In the following examples, a roff fragment is fed into @L_ROFF@ via
standard input.
As we are only interested in the diagnostic messages (standard error)
on the terminal, the normal formatted output (standard output) is
redirected to the nirvana device
.IR /dev/null .
The resulting diagnostic messages are displayed directly below the
corresponding example.
.
.\"
.SS "Command line option"
.
Example:
.
.RS
.P
.EX
\fIsh#\fP echo '.
> .de test_macro
> ..
> .test_macro
> .test_macro some dummy arguments
> ' | @L_ROFF@ -m trace >/dev/null

*** .de test_macro
*** de trace enter: .test_macro
*** trace exit: .test_macro
*** de trace enter: .test_macro "some" "dummy" "arguments"
*** trace exit: .test_macro "some" "dummy" "arguments"
.EE
.RE
.
.P
The entry and the exit of each macro call is displayed on the terminal
(standard output) \[em] together with the arguments (if any).
.
.\"
.SS "Nested macro calls"
.
Example:
.
.RS
.P
.EX
\fIsh#\fP echo '.
> .de child
> ..
> .de parent
> .child
> ..
> .parent
> ' | @L_ROFF@ -m trace >/dev/null

*** .de child
*** .de parent
*** de trace enter: .parent
 *** de trace enter: .child
 *** trace exit: .child
*** trace exit: .parent
.EE
.RE
.
.P
This shows that macro calls can be nested.
This powerful feature can help to tack down quite complex call stacks.
.
.\"
.SS "Activating with .mso"
.
Example:
.
.RS
.P
.EX
\fIsh#\fP echo '.
> .de before
> ..
> .mso trace.tmac
> .de after
> ..
> .before
> .after
> .before
>  ' | @L_ROFF@ >/dev/null

*** de trace enter: .after
*** trace exit: .after
.EE
.RE
.
.P
Here, the tracing is activated within the document, not by a command
line option.
As tracing was not active when macro
.I before
was defined, no call of this macro is protocolled; on the other hand,
the macro
.I after
is fully protocolled.
.
.\"
.SH PROBLEMS
.
Because
.B trace.tmac
wraps the
.B .de
request (and its cousins), macro arguments are expanded one level more.
This causes problems if an argument contains four backslashes or more
to prevent too early expansion of the backslash.  For example, this
macro call
.
.IP
.EX
\&.foo \e\e\e\en[bar]
.EE
.
.P
normally passes `\e\en[bar]' to macro `.foo', but with the redefined
.B .de
request it passes `\en[bar]' instead.
.
.P
The solution to this problem is to use @L_ROFF@'s
.B \eE
escape which is an escape character not interpreted in copy mode, for
example
.
.IP
.EX
\&.foo \eEn[bar]
.EE
.
.\"
.SH FILES
.
The
.I trace
macros are kept in the file
.B trace.tmac
located in the
.IR "tmac directory" ;
see
.BR @L_ROFF@-tmac (@MAN5EXT@)
for details.
.
.\"
.SH ENVIRONMENT
.
.TP
.B $@U_ROFF@_TMAC_PATH
A colon-separated list of additional tmac directories in which to
search for macro files; see
.BR @L_ROFF@-tmac (@MAN5EXT@)
for details.
.
.\"
.SH AUTHOR
.
Copyright (c) 2014 - 2017 Steffen (Daode) Nurpmeso <steffen@sdaoden.eu>.
.br
Copyright (C) 2002, 2006 - 2008 Free Software Foundation, Inc.
.br
This document was written by Bernd Warken.
.P
This document is distributed under the terms of the FDL (GNU Free
Documentation License) version 1.1 or later.
.
You should have received a copy of the FDL on your system, it is also
available on-line at the
.UR http://\:www.gnu.org/\:copyleft/\:fdl.html
GNU copyleft site
.UE .
.
.\"
.SH "SEE ALSO"
.
.TP
.BR @L_ROFF@ (@MAN1EXT@)
An overview of the @T_ROFF@ system.
.
.TP
.BR @L_TROFF@ (@MAN1EXT@)
For details on option
.BR \-m .
.
.TP
.BR @L_ROFF@-tmac (@MAN5EXT@)
A general description of @T_ROFF@ macro packages.
.
.TP
.BR @L_ROFF@ (@MAN7EXT@)
A short reference for the @T_ROFF@ formatting language.
.
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