trace(3NCURSES) Library calls trace(3NCURSES)
NAME
curses_trace, trace, _tracef, _traceattr, _traceattr2, _tracecchar_t,
_tracecchar_t2, _tracechar, _tracechtype, _tracechtype2, _nc_tracebits,
_tracedump, _tracemouse - curses debugging routines
SYNOPSIS
#include <curses.h>
unsigned curses_trace(const unsigned trace-mask);
void _tracef(const char *format, ...);
char *_traceattr(attr_t attr);
char *_traceattr2(int buffer, chtype ch);
char *_tracecchar_t(const cchar_t *string);
char *_tracecchar_t2(int buffer, const cchar_t *string);
char *_tracechar(int c);
char *_tracechtype(chtype ch);
char *_tracechtype2(int buffer, chtype ch);
void _tracedump(const char *label, WINDOW *win);
char *_nc_tracebits(void);
char *_tracemouse(const MEVENT *event);
/* deprecated */
void trace(const unsigned int trace-mask);
DESCRIPTION
The curses trace routines are used for debugging the ncurses libraries,
as well as applications which use the ncurses libraries. Some limita-
tions apply:
• Aside from curses_trace, the other functions are normally available
only with the debugging library e.g., libncurses_g.a.
All of the trace functions may be compiled into any model (shared,
static, profile) by defining the symbol TRACE.
• Additionally, the functions which use cchar_t are only available
with the wide-character configuration of the libraries.
Functions
The principal parts of this interface are
• curses_trace, which selectively enables different tracing features,
and
• _tracef, which writes formatted data to the trace file.
The other functions either return a pointer to a string-area (allo-
cated by the corresponding function), or return no value (such as
_tracedump, which implements the screen dump for TRACE_UPDATE). The
caller should not free these strings, since the allocation is reused
on successive calls. To work around the problem of a single string-
area per function, some use a buffer-number parameter, telling the
library to allocate additional string-areas.
The curses_trace function is always available, whether or not the other
trace functions are available:
• If tracing is available, calling curses_trace with a nonzero parame-
ter updates the trace mask, and returns the previous trace mask.
When the trace mask is nonzero, ncurses creates the file “trace” in
the current directory for output. If the file already exists, no
tracing is done.
• If tracing is not available, curses_trace returns zero (0).
Trace Parameter
The trace parameter is formed by logically “or”-ing values from the list
of TRACE_xxx definitions in <curses.h>. These include:
TRACE_DISABLE
turn off tracing by passing a zero parameter.
The library flushes the output file, but retains an open file-de-
scriptor to the trace file so that it can resume tracing later if a
nonzero parameter is passed to the curses_trace function.
TRACE_TIMES
trace user and system times of updates.
TRACE_TPUTS
trace tputs(3NCURSES) calls.
TRACE_UPDATE
trace update actions, old & new screens.
TRACE_MOVE
trace cursor movement and scrolling.
TRACE_CHARPUT
trace all character outputs.
TRACE_ORDINARY
trace all update actions. The old and new screen contents are
written to the trace file for each refresh.
TRACE_CALLS
trace all curses calls. The parameters for each call are traced,
as well as return values.
TRACE_VIRTPUT
trace virtual character puts, i.e., calls to addch.
TRACE_IEVENT
trace low-level input processing, including timeouts.
TRACE_BITS
trace state of TTY control bits.
TRACE_ICALLS
trace internal/nested calls.
TRACE_CCALLS
trace per-character calls.
TRACE_DATABASE
trace read/write of terminfo/termcap data.
TRACE_ATTRS
trace changes to video attributes and colors.
TRACE_MAXIMUM
maximum trace level, enables all of the separate trace features.
Some tracing features are enabled whenever the curses_trace parameter is
nonzero. Some features overlap. The specific names are used as a
guideline.
Command-line Utilities
The command-line utilities such as tic(1) provide a verbose option which
extends the set of messages written using the curses_trace function.
Both of these (-v and curses_trace) use the same variable (_nc_tracing),
which determines the messages which are written.
Because the command-line utilities may call initialization functions
such as setupterm, tgetent or use_extended_names, some of their debug-
ging output may be directed to the trace file if the NCURSES_TRACE envi-
ronment variable is set:
• messages produced in the utility are written to the standard error.
• messages produced by the underlying library are written to trace.
If ncurses is built without tracing, none of the latter are produced,
and fewer diagnostics are provided by the command-line utilities.
RETURN VALUE
Routines which return a value are designed to be used as parameters to
the _tracef routine.
ENVIRONMENT
NCURSES_TRACE
A positive integral value stored in this variable causes the following
functions to enable the tracing feature as if curses_trace were called.
filter, initscr, new_prescr, newterm, nofilter, restartterm,
ripoffline, setupterm, slk_init, tgetent, use_env,
use_extended_names, use_tioctl
PORTABILITY
These functions are not part of the X/Open Curses interface. Some other
curses implementations are known to have similar features, but they are
not compatible with ncurses:
• SVr4 provided traceon and traceoff, to control whether debugging in-
formation was written to the “trace” file. While the functions were
always available, this feature was only enabled if DEBUG was defined
when building the library.
The SVr4 tracing feature is undocumented.
• PDCurses provides traceon and traceoff, which (like SVr4) are always
available, and enable tracing to the “trace” file only when a debug-
library is built.
PDCurses has a short description of these functions, with a note
that they are not present in X/Open Curses, ncurses or NetBSD. It
does not mention SVr4, but the functions' inclusion in a header file
section labeled “Quasi-standard” hints at the origin.
• NetBSD does not provide functions for enabling/disabling traces. It
uses environment variables CURSES_TRACE_MASK and CURSES_TRACE_FILE
to determine what is traced, and where the results are written.
This is available only when a debug-library is built.
The NetBSD tracing feature is undocumented.
A few ncurses functions are not provided when symbol versioning is used:
_nc_tracebits, _tracedump, _tracemouse
The original trace routine was deprecated because it often conflicted
with application names.
SEE ALSO
ncurses(3NCURSES)
ncurses 6.5 2025-01-18 trace(3NCURSES)
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