Warning diagnostics emitted by troff are divided into named,
numbered categories. The name associated with each warning
category is used by the -w and -W options. Each category is also
assigned a power of two; the sum of enabled category codes is
used by the warn request and the .warn register. Warnings of
each category are produced under the following circumstances.
┌──────────────────────┬─────────────────────────────┐
│Bit Code Category │ Bit Code Category │
├──────────────────────┼─────────────────────────────┤
│ 0 1 char │ 10 1024 reg │
│ 1 2 number │ 11 2048 tab │
│ 2 4 break │ 12 4096 right-brace │
│ 3 8 delim │ 13 8192 missing │
│ 4 16 el │ 14 16384 input │
│ 5 32 scale │ 15 32768 escape │
│ 6 64 range │ 16 65536 space │
│ 7 128 syntax │ 17 131072 font │
│ 8 256 di │ 18 262144 ig │
│ 9 512 mac │ 19 524288 color │
│ │ 20 1048576 file │
└──────────────────────┴─────────────────────────────┘
break 4 When filling is enabled, a line could not be
broken such that its length was less than the
output line length \n[.l]. This is enabled
by default.
char 1 An undefined glyph was requested for output.
('char' is a misnomer since it reports
missing glyphs—there are no 'missing' input
characters, only invalid ones.) This
cateogry is enabled by default.
color 524288 An undefined color was dereferenced, an
attempt was made to define a color using an
unrecognized color space, an invalid
component in a color definition was
encountered, or an attempt was made to
redefine the default color.
delim 8 The closing delimiter in an escape sequence
was missing or mismatched.
di 256 A di, da, box, or boxa request was invoked
without an argument when there was no current
diversion.
el 16 The el request was encountered with no prior
corresponding ie request.
escape 32768 An unsupported escape sequence was
encountered. In such a sequence \X, the
escape character is ignored and X is output.
file 1048576 An attempt was made to load a file that does
not exist. This category is enabled by
default.
font 131072 A non-existent font was dereferenced. This
category is enabled by default.
ig 262144 An invalid escape sequence occurred in input
ignored using the ig request. This warning
category diagnoses a condition that is an
error when it occurs in non-ignored input.
input 16384 An invalid character occurred on the input
stream.
mac 512 An undefined string, macro, diversion, or box
was used. When such an object is
dereferenced, an empty object of that name is
automatically created. So, in most cases, at
most one warning is given for each name.
This warning is also emitted upon an attempt
to move an unplanted trap. In such cases,
the unplanted macro is not dereferenced, so
it is not created if it does not exist.
missing 8192 A request was invoked with a mandatory
argument absent.
number 2 An invalid numeric expression was
encountered. This category is enabled by
default.
range 64 A numeric expression was out of range for its
context.
reg 1024 An undefined register was used. When an
undefined register is dereferenced, it is
automatically defined with a value of 0. So,
in most cases, at most one warning is given
for each name.
right-brace 4096 A right brace escape sequence \} was
encountered where a number was expected.
scale 32 An inappropriate scaling indicator was used
in a numeric expression.
space 65536 A space was missing between a request or
macro and its argument. This warning is
produced when an undefined name longer than
two characters is encountered and the first
two characters of the name constitute a
defined name. No request is invoked, no
macro called, and an empty macro is not
defined. This category is enabled by
default. It never occurs in compatibility
mode.
syntax 128 A self-contradictory hyphenation mode was
requested; an empty or incomplete numeric
expression was encountered; an operand to a
numeric operator was missing; an attempt was
made to define a recursive, empty, or
nonsensical character class; or a groff
extension conditional expression operator was
used while in compatibility mode.
tab 2048 A tab character was encountered where a
number was expected, or appeared in an
unquoted macro argument.
Two warning names group other warning categories for convenience.
all All warning categories except di, mac, and reg. This
shorthand is intended to produce all warnings that are
useful with macro packages written for AT&T troff and its
descendants, which have less fastidious diagnostics than
GNU troff.
w All warning categories. Authors of documents and macro
packages targeting groff are encouraged to use this
setting.
