16.3 Macro Details and Caveats

By design, macro expansion should not happen in the following contexts:

• @macro and @unmacro lines;
• @if... lines, including @ifset and similar;
• @set, @clear, @value;
• @clickstyle lines;
• @end lines when there is no macro expansion in the block command.

Unfortunately, TeX may do some expansion in these situations, possibly yielding errors.

Also, quite a few macro-related constructs cause problems with TeX; some of the caveats are listed below. Thus, if you get macro-related errors when producing the printed version of a manual, you might try expanding the macros with texi2any by invoking texi2dvi with the ‘-E’ option (see Format with texi2dvi). Or, more reliably, eschew Texinfo macros altogether and use a language designed for macro processing, such as M4 (see External Macro Processors: Line Directives).

• As mentioned earlier, macro names must consist entirely of letters.
• It is not advisable to redefine any TeX primitive, plain, or Texinfo command name as a macro. Unfortunately, this is a large and open-ended set of names, and the possible resulting errors are unpredictable.
• Arguments to macros taking more than one argument cannot cross lines.
• Macros containing a command which must be on a line by itself, such as a conditional, cannot be invoked in the middle of a line. Similarly, macros containing line-oriented commands or text, such as @example environments, may behave unpredictably in TeX.
• If you have problems using conditionals within a macro, an alternative is to use separate macro definitions inside conditional blocks. For example, instead of

  @macro Mac
  @iftex
  text for TeX output
  @end iftex
  @ifnottex
  text for not TeX output
  @end ifnottex
  @end macro
  

  you can do the following instead:

  @iftex
  @macro Mac
  text for TeX output
  @end macro
  @end iftex
  
  @ifnottex
  @macro Mac
  text for not TeX output
  @end macro
  @end ifnottex
  

• Texinfo commands in the expansion of a macro in the text of an index entry may end up being typeset as literal text (including an “@” sign), instead of being interpreted with their intended meaning.
• White space is ignored at the beginnings of lines.
• Macros can’t be reliably used in the argument to accent commands (see Inserting Accents).
• The backslash escape for commas in macro arguments does not work; @comma{} must be used.
• Ending a macro body with ‘@c’ may cause text following the macro invocation to be ignored as a comment in texi2any. This is not the case when processing with TeX. This was often done to “comment out” an unwanted newline at the end of a macro body, but this is not necessary any more, as the final newline before ‘@end macro’ is not included in the macro body anyway.
• In general, you can’t arbitrarily substitute a macro (or @value) call for Texinfo command arguments, even when the text is the same. Texinfo is not M4 (or even plain TeX). It might work with some commands, it fails with others. Best not to do it at all. For instance, this fails:

  @macro offmacro
  off
  @end macro
  @headings @offmacro
  

  This looks equivalent to @headings off, but for TeXnical reasons, it fails with a mysterious error message (namely, ‘Paragraph ended before @headings was complete’).

• Macros cannot define macros in the natural way. To do this, you must use conditionals and raw TeX. For example:

  @ifnottex
  @macro ctor {name, arg}
  @macro \name\
  something involving \arg\ somehow
  @end macro
  @end macro
  @end ifnottex
  @tex
  \gdef\ctor#1{\ctorx#1,}
  \gdef\ctorx#1,#2,{\def#1{something involving #2 somehow}}
  @end tex
  

The following limitations are by design:

• If you want to pass an argument with the Texinfo command @, (to produce a cedilla, see Inserting Accents), you have to use @value or another workaround. Otherwise, the comma may be taken as separating the arguments. With texi2any, the comma can be escaped by a backslash. With TeX another workaround need to be used, therefore we recommend using such a workaround.

  For example,

  @macro mactwo{argfirst, argsecond}
  \argfirst\+\argsecond\.
  @end macro
  @set fc Fran@,cois
  @mactwo{@value{fc},}
  

  produces:

  François+.
  

• @verbatim and macros do not mix; for instance, you can’t start a verbatim block inside a macro and end it outside (see @verbatim: Literal Text). Starting any environment inside a macro and ending it outside may or may not work, for that matter.
• Macros that completely define macros are ok, but it’s not possible to have incompletely nested macro definitions. That is, @macro and @end macro (likewise for @rmacro) must be correctly paired. For example, you cannot start a macro definition within a macro, and then end that nested definition outside the macro.

In the makeinfo implementation before Texinfo 5.0, ends of lines from expansion of a @macro definition did not end an @-command line-delimited argument (@chapter, @center, etc.). This is no longer the case. For example:

@macro twolines{}
aaa
bbb
@end macro
@center @twolines{}

In the current texi2any, this is equivalent to:

@center aaa
bbb

with just ‘aaa’ as the argument to @center. In the earlier implementation, it would have been parsed as this:

@center aaa bbb