给定一个文件xref-and-value.texi，其内容为：
\input texinfo @c -*- TeX-PDF-mode: t; -*-
@setfilename xref-and-value.info
@settitle @code{@@xref} and @code{@@value} in \pdftex
@set fngccint gccint-4.6
@xref{Top,,Introduction, @value{fngccint}, GNU Compiler Collection (GCC) Internals}.
@bye
我得到这个输出pdfTeX：
This is pdfTeX, Version 3.1415926-1.40.10 (TeX Live 2009/Debian) (format=pdftex 2012.2.28) 5 MAR 2012 17:13
entering extended mode
%&-line parsing enabled.
**\input xref-and-value.texi
(./xref-and-value.texi (/usr/share/texmf/tex/texinfo/texinfo.tex
Loading texinfo [version 2008-04-18.10]:
...
formatting,
\defaultparindent=\dimen46
and turning on texinfo input format.)
(./xref-and-value.aux)
\openout1 = `xref-and-value.aux'.
@cpindfile=@write2
@fnindfile=@write3
@vrindfile=@write4
@tpindfile=@write5
@kyindfile=@write6
@pgindfile=@write7
! TeX capacity exceeded, sorry [input stack size=5000].
@makevalueexpandable ->@let @value
= @expandablevalue @catcode `@-=@other @c...
@value ->@begingroup @makevalueexpandable
@valuexxx
@makevalueexpandable ->@let @value
= @expandablevalue @catcode `@-=@other @c...
@value ->@begingroup @makevalueexpandable
@valuexxx
@makevalueexpandable ->@let @value
= @expandablevalue @catcode `@-=@other @c...
@value ->@begingroup @makevalueexpandable
@valuexxx
...
l.6 ...}, GNU Compiler Collection (GCC) Internals}
.
If you really absolutely need more capacity,
you can ask a wizard to enlarge me.
! ==> Fatal error occurred, no output PDF file produced!
因此，看起来第 4 个参数是@xref在仅扩展上下文中使用，但它@value并不（有用地）可扩展。
是否可以重新实施该设施@set，@value以便@value 是可以扩展吗？
更新：
为了回应 Bruno 的评论@expandablevalue，我尝试了这个：
\errorcontextlines 100 \input texinfo @c -*- TeX-PDF-mode: t; -*-
@setfilename xref-and-value.info
@settitle @code{@@xref} and @code{@@value} in \pdftex
@set fngccint gccint-4.6
@xref{Top,,Introduction, @expandablevalue{fngccint}, GNU Compiler Collection (GCC) Internals}.
@bye
这至少可以进行排版，但仍然会产生错误：
! Argument of @expandablevalue has an extra }.
<inserted text>
@par
<to be read again>
}
@addtokens ...f @addtoks {@noexpand #1={@the #1#2}
}@addtoks
@skipspaces ...@else @addtokens {@filename }{@PP }
@advance @filenamelength b...
<argument> @expandablevalue
{fngccint}
@getfilename ...ngth =0@expandafter @skipspaces #1
|@relax
@xrefX ...nofonts @turnoffactive @getfilename {#4}
{@activebackslashdouble @x...
l.7 ...}, GNU Compiler Collection (GCC) Internals}
.
I've run across a `}' that doesn't seem to match anything.
For example, `\def\a#1{...}' and `\a}' would produce
this error. If you simply proceed now, the `\par' that
I've just inserted will cause me to report a runaway
argument that might be the root of the problem. But if
your `}' was spurious, just type `2' and it will go away.
Runaway argument?
! Paragraph ended before @expandablevalue was complete.
<to be read again>
@par
<to be read again>
}
@addtokens ...f @addtoks {@noexpand #1={@the #1#2}
}@addtoks
@skipspaces ...@else @addtokens {@filename }{@PP }
@advance @filenamelength b...
<argument> @expandablevalue
{fngccint}
@getfilename ...ngth =0@expandafter @skipspaces #1
|@relax
@xrefX ...nofonts @turnoffactive @getfilename {#4}
{@activebackslashdouble @x...
l.7 ...}, GNU Compiler Collection (GCC) Internals}
.
I suspect you've forgotten a `}', causing me to apply this
control sequence to too much text. How can we recover?
My plan is to forget the whole thing and hope for the best.
答案1
的第四个参数@xref被解析为文件名@getfilename（要查看，请#4在 的日志输出中查找@show@xref）。此函数一次读取一个宏参数，并独立扩展这些参数。当收到 时@expandablevalue{fngccint}，它将首先读取@expandablevalue并尝试扩展它（在 内@edef），但会失败，因为{fngccint}不在该 内@edef。
一种解决方案是在 : 周围加上括号@expandablevalue{fngccint}，然后将其作为一个宏参数抓取，然后扩展就可以起作用了。
\errorcontextlines 100 \input texinfo @c -*- TeX-PDF-mode: t; -*-
@setfilename xref-and-value.info
@settitle @code{@@xref} and @code{@@value} in \pdftex
@set fngccint gccint-4.6
@xref{Top,,Introduction, {@expandablevalue{fngccint}}, GNU Compiler Collection (GCC) Internals}.
@bye
答案2
顺便说一句，如果以后有人遇到这个问题，已修复texinfo.tex，因此您可以直接获取最新版本texinfo.tex并使用它。（这实际上是上游建议的每个人texinfo.tex做；只需搜索Texinfo 网页）