The warnings that can be given to gtroff are divided into the
following categories. The name associated with each warning is used by
the -w and -W options; the number is used by the
warn request and by the .warn register.
Non-existent glyphs.27 This is enabled by default.
Invalid numeric expressions. This is enabled by default. See Expressions.
In fill mode, lines that could not be broken so that their length was less than the line length. This is enabled by default.
Missing or mismatched closing delimiters.
Use of the el request with no matching ie request.
See if-else.
Meaningless scaling indicators.
Out of range arguments.
Dubious syntax in numeric expressions.
Use of di or da without an argument when there is no
current diversion.
Use of undefined strings, macros and diversions. When an undefined string, macro, or diversion is used, that string is automatically defined as empty. So, in most cases, at most one warning is given for each name.
Use of undefined number registers. When an undefined number register is used, that register is automatically defined to have a value of 0. So, in most cases, at most one warning is given for use of a particular name.
Use of a tab character where a number was expected.
Use of \} where a number was expected.
Requests that are missing non-optional arguments.
Invalid input characters.
Unrecognized escape sequences. When an unrecognized escape sequence
\X is encountered, the escape character is ignored, and
X is printed.
Missing space between a request or macro and its argument. This warning is given when an undefined name longer than two characters is encountered, and the first two characters of the name make a defined name. The request or macro is not invoked. When this warning is given, no macro is automatically defined. This is enabled by default. This warning never occurs in compatibility mode.
Non-existent fonts. This is enabled by default.
Invalid escapes in text ignored with the ig request. These are
conditions that are errors when they do not occur in ignored text.
Color related warnings.
Missing files. The mso request gives this warning when the
requested macro file does not exist. This is enabled by default.
All warnings except ‘di’, ‘mac’ and ‘reg’. It is intended that this covers all warnings that are useful with traditional macro packages.
All warnings.