我升级到了 v2.1，siunitx因为 ubuntu 的包管理器版本（1.3？）太旧了。似乎出了问题。安装时可能出了问题，或者缺少依赖项等。我无法很好地阅读日志文件来找出问题所在。
.dtx我通过将文件复制到我的本地 texmf 树texmf/tex/latex/siunitx/，然后tex siunitx.sty从该目录运行来安装它。
当我尝试使用该包时，出现此错误：
! Undefined control sequence.
\siunitx_cs_if_macro:NT #1->\exp_last_unbraced:No
\siunitx_cs_if_tl_aux:w {\...
l.6 \begin{document}
Runaway argument?
{\token_to_meaning:N \bar macro\q_stop }{\prg_return_true: }{\prg_return_false: \ETC.
! Paragraph ended before \siunitx_cs_if_tl_aux:w was complete.
<to be read again>
\par
l.7
这是\listfiles
*File List*
article.cls 2007/10/19 v1.4h Standard LaTeX document class
size10.clo 2007/10/19 v1.4h Standard LaTeX file (size option)
siunitx.sty 2010/11/24 v2.1f A comprehensive (SI) units package
expl3.sty 2009/08/12 v1458 L3 Experimental code bundle wrapper
l3names.sty 2009/08/08 v1452 L3 Experimental Naming Scheme for TeX Primitives
l3basics.sty 2009/08/08 v1453 L3 Experimental basic definitions
l3expan.sty 2009/08/16 v1464 L3 Experimental Argument Expansion module
l3tl.sty 2009/09/03 v1505 L3 Experimental Token Lists
l3num.sty 2009/08/08 v1451 L3 Experimental token numbers
l3intexpr.sty 2009/03/20 v1086 L3 Integer Expressions
l3quark.sty 2009/05/31 v1365 L3 Experimental Quark Commands
l3seq.sty 2009/06/17 v1415 L3 Experimental sequences and stacks
l3toks.sty 2009/06/14 v1412 L3 Experimental Token Registers
l3int.sty 2009/05/28 v1362 L3 Experimental Integer module
l3prg.sty 2009/09/20 v1545 L3 Experimental control structures
l3clist.sty 2009/08/05 v1441 L3 Experimental comma separated lists
l3token.sty 2009/09/22 v1550 L3 Experimental token investigation and manipulation
l3io.sty 2009/05/31 v1369 L3 Experimental i/o module
l3prop.sty 2009/09/16 v1536 L3 Experimental Property Lists
l3msg.sty 2009/09/01 v1502 L3 Experimental LaTeX Messages module
l3skip.sty 2009/05/28 v1362 L3 Experimental skip registers
l3box.sty 2009/06/01 v1375 L3 Experimental Box module
l3keyval.sty 2009/07/13 v1424 L3 Experimental keyval processing
l3keys.sty 2009/09/17 v1542 L3 Experimental key-value support
l3precom.sty 2009/08/08 v1453 L3 Experimental precompilation module
l3calc.sty 2009/05/28 v1362 L3 Experimental calc module
l3xref.sty 2009/05/28 v1362 L3 Experimental cross referencing
l3file.sty 2009/05/28 v1352 L3 Experimental file loading
amstext.sty 2000/06/29 v2.01
amsgen.sty 1999/11/30 v2.0
array.sty 2008/09/09 v2.4c Tabular extension package (FMi)
l3keys2e.sty 2009/08/24 v1494 Parsing LaTeX3 keyvals as LaTeX2e package options
xparse.sty 2009/08/31 v1497 Generic document command parser
translator.sty 2007/03/11 ver 1.00
keyval.sty 1999/03/16 v1.13 key=value parser (DPC)
translator-language-mappings.tex
还有一个 MWE：
\documentclass{article}
\listfiles
\usepackage{siunitx}
\begin{document}
Foo
\end{document}