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* doc/autoconf.texi (Here-Documents): New section, gathering
documentation about here-documents. Use `href', not `uref', and other changes.
This commit is contained in:
Akim Demaille
parent
a57d9b390d
commit
0abdfb5a9d
@ -1,3 +1,9 @@
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2001-06-09 Akim Demaille <akim@epita.fr>
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* doc/autoconf.texi (Here-Documents): New section, gathering
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documentation about here-documents.
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Use `href', not `uref', and other changes.
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2001-06-09 Akim Demaille <akim@epita.fr>
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* doc/autoconf.texi (Portable Shell Programming): Promoted as a
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11
TODO
11
TODO
@ -7,7 +7,7 @@ these suggestions... their presence here doesn't imply my endorsement.
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------------------------------------------------------------------------------
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* Autoconf 2.51
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* Soon
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** --target & AC_ARG_PROGRAM
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Shouldn't *any* `program' be installed as `$target_alias-program' even
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@ -15,7 +15,7 @@ if AC_ARG_PROGRAM is not called? That would be much more predictable.
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Ian?
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** Document
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Automake, Libtool, AC_ARG_VAR.
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AC_ARG_VAR, m4_pattrern_*
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** RedHat's Autoconf page
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should be removed.
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@ -23,6 +23,11 @@ should be removed.
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** AC_CHECK_TOOL...
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Write a test that checks that it honors the values set by the user.
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* Autoconf 2.52 or later
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** Languages
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Integrate other Fortrans etc.
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** AC_CHECK_FUNCS and AC_TRY_LINK_FUNC
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I have still not understood what's the difference between the two
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which requires to have two different sources: AC_LANG_CALL and
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@ -48,8 +53,6 @@ specializing macros will call them. OTOH, this doubles our work,
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since specializing macros will save us from additional typing. But
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the more powerful autoscan is, the better...
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* Autoconf 2.51 or later
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** Libtool
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Define once for all the hooks they need, any redefinition of
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AC_PROG_CC etc. is way too dangerous and too limiting. The GCC team
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@ -273,6 +273,7 @@ Checking Run Time Behavior
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Portable Shell Programming
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* Shellology:: A zoology of shells
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* Here-Documents:: Quirks and tricks
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* File Descriptors:: FDs and redirections
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* File System Conventions:: File- and pathnames
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* Shell Substitutions:: Variable and command expansions
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@ -603,28 +604,29 @@ the GNU build tools.
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@item Web
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The home pages for
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@uref{http://www.gnu.org/software/autoconf/,Autoconf},
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@uref{http://www.gnu.org/software/automake/,Automake}, and
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@uref{http://www.gnu.org/software/libtool/,Libtool}.
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@href{http://www.gnu.org/software/autoconf/,Autoconf},
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@href{http://www.gnu.org/software/automake/,Automake}, and
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@href{http://www.gnu.org/software/libtool/,Libtool}.
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@item Automake Manual (TeXinfo)
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@item Automake Manual
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@xref{Top,,Automake,automake,GNU Automake}, for more
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information on Automake.
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@item Books
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The book @cite{GNU Autoconf, Automake and Libtool}, by G. V. Vaughan,
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B. Elliston, T. Tromey, and I. L. Taylor (New Riders, 2000) (ISBN
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1578701902) describes the complete GNU build environment. You can also
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find the entire book on-line at
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@uref{http://sources.redhat.com/autobook/,``The Goat Book'' home page}.
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The book @cite{GNU Autoconf, Automake and Libtool}@footnote{@cite{GNU
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Autoconf, Automake and Libtool}, by G. V. Vaughan, B. Elliston,
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T. Tromey, and I. L. Taylor. New Riders, 2000, ISBN 1578701902.}
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describes the complete GNU build environment. You can also find the
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entire book on-line at @href{http://sources.redhat.com/autobook/,``The
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Goat Book'' home page}.
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@item Tutorials and Examples
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The @uref{http://sources.redhat.com/autoconf/,Autoconf Developer Page}
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The @href{http://sources.redhat.com/autoconf/,Autoconf Developer Page}
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maintains links to a number of Autoconf/Automake tutorials online, and
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also links to the @uref{http://www.gnu.org/software/ac-archive/,
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also links to the @href{http://www.gnu.org/software/ac-archive/,
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Autoconf Macro Archive}.
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@end itemize
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@ -1289,17 +1291,18 @@ The @var{format} gives you a lot of freedom:
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@example
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@group
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$ autoconf -t 'AC_SUBST:ac_subst@{"$1"@} = "$f:$l";'
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ac_subst@{"ECHO_C"@} = "configure.ac:2";
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ac_subst@{"ECHO_N"@} = "configure.ac:2";
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ac_subst@{"ECHO_T"@} = "configure.ac:2";
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$ autoconf -t 'AC_SUBST:$$ac_subst@{"$1"@} = "$f:$l";'
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$ac_subst@{"ECHO_C"@} = "configure.ac:2";
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$ac_subst@{"ECHO_N"@} = "configure.ac:2";
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$ac_subst@{"ECHO_T"@} = "configure.ac:2";
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@i{More traces deleted}
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@end group
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@end example
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@noindent
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A long @var{separator} can be used to improve the readability of complex
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structures:
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structures, and to ease its parsing (for instance when no single
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character is suitable as a separator)):
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@example
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@group
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@ -4724,7 +4727,7 @@ if the system supports @samp{#!}, @samp{no} if not.
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@cvindex _LARGE_FILES
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@ovindex CC
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Arrange for
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@uref{http://www.sas.com/standards/large.file/x_open.20Mar96.html,
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@href{http://www.sas.com/standards/large.file/x_open.20Mar96.html,
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large-file support}. On some hosts, one must use special compiler
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options to build programs that can access large files. Append any such
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options to the output variable @code{CC}. Define
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@ -5295,6 +5298,7 @@ Some of these external utilities have a portable subset of features; see
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@menu
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* Shellology:: A zoology of shells
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* Here-Documents:: Quirks and tricks
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* File Descriptors:: FDs and redirections
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* File System Conventions:: File- and pathnames
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* Shell Substitutions:: Variable and command expansions
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@ -5305,7 +5309,7 @@ Some of these external utilities have a portable subset of features; see
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* Limitations of Make:: Portable Makefiles
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@end menu
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@node Shellology, File Descriptors, Portable Shell, Portable Shell
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@node Shellology, Here-Documents, Portable Shell, Portable Shell
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@section Shellology
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There are several families of shells, most prominently the Bourne
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@ -5358,15 +5362,6 @@ To detect whether you are running @command{bash}, test if
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Mode,, Bash @sc{posix} Mode, bash, The GNU Bash Reference Manual}, for
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details.
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@item @command{/bin/sh} on OpenBSD
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@cindex @command{/bin/sh} on OpenBSD
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@samp{\"} expands to @samp{"} in here-documents with unquoted
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delimiter in the native @command{/bin/sh} on OpenBSD 2.7. As a general
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rule, if @samp{\\} expands to @samp{\} use @samp{\\} to get @samp{\}.
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Don't rely on @samp{\} being preserved just because it has no special
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meaning together with the next symbol.
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@item @command{/usr/xpg4/bin/sh} on Solaris
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@cindex @command{/usr/xpg4/bin/sh} on Solaris
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The @sc{posix}-compliant Bourne shell on a Solaris system is
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@ -5381,6 +5376,8 @@ To detect whether you are running @command{zsh}, test if
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compatible with the Bourne shell: you have to run @samp{emulate sh} and
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set @code{NULLCMD} to @samp{:}. @xref{Compatibility,, Compatibility,
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zsh, The Z Shell Manual}, for details.
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Zsh 3.0.8 is the native @command{/bin/sh} on Mac OS X 10.0.3.
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@end table
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The following discussion between Russ Allbery and Robert Lipe is worth
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@ -5411,7 +5408,77 @@ So while most modern systems do have a shell _somewhere_ that meets the
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@sc{posix} standard, the challenge is to find it.
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@end quotation
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@node File Descriptors, File System Conventions, Shellology, Portable Shell
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@node Here-Documents, File Descriptors, Shellology, Portable Shell
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@section Here-Documents
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Don't rely on @samp{\} being preserved just because it has no special
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meaning together with the next symbol. in the native @command{/bin/sh}
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on OpenBSD 2.7 @samp{\"} expands to @samp{"} in here-documents with
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unquoted delimiter. As a general rule, if @samp{\\} expands to @samp{\}
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use @samp{\\} to get @samp{\}.
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With OpenBSD 2.7's @command{/bin/sh}
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@example
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@group
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$ cat <<EOF
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> \" \\
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> EOF
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" \
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@end group
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@end example
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@noindent
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and with Bash:
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@example
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@group
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bash-2.04$ cat <<EOF
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> \" \\
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> EOF
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\" \
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@end group
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@end example
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Many older shells (including the Bourne shell) implement here-documents
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inefficiently. Users can generally speed things up by using a faster
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shell, e.g., by using the command @samp{bash ./configure} rather than
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plain @samp{./configure}.
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Some shells can be extremely inefficient when there are a lot of
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here-documents inside a single statement. For instance if your
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@file{configure.ac} includes something like:
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@example
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@group
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if <cross_compiling>; then
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assume this and that
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else
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check this
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check that
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check something else
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on and on forever
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fi
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@end group
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@end example
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A shell parses the whole @code{if}/@code{fi} construct, creating
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temporary files for each here document in it. Some shells create links
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for such here-documents on every @code{fork ()}, so that the clean-up
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code they had installed correctly removes them. It is creating the
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links that the shell can take forever.
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Moving the tests out of the @code{if}/@code{fi}, or creating multiple
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@code{if}/@code{fi} constructs, would improve the performance
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significantly. Anyway, this kind of construct is not exactly the
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typical use of Autoconf. In fact, it's even not recommended, because M4
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macros can't look into shell conditionals, so we may fail to expand a
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macro when it was expanded before in a conditional path, and the
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condition turned out to be false at run-time, and we end up not
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executing the macro at all.
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@node File Descriptors, File System Conventions, Here-Documents, Portable Shell
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@section File Descriptors
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Some file descriptors shall not be used, since some systems, admittedly
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@ -5527,10 +5594,10 @@ or @samp{;}) when it starts up.
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File names need extra care as well. While @sc{dos}-based environments
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that are Unixy enough to run @command{autoconf} (such as DJGPP) will
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usually be able to handle long file names properly, there are still
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limitations that can seriously break packages. Several of these issues can
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be easily detected by
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@uref{ftp://ftp.gnu.org/gnu/non-gnu/doschk/doschk-1.1.tar.gz, the doschk
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package}.
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limitations that can seriously break packages. Several of these issues
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can be easily detected by the
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@href{ftp://ftp.gnu.org/gnu/non-gnu/doschk/doschk-1.1.tar.gz, doschk}
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package.
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A short overview follows; problems are marked with @sc{sfn}/@sc{lfn} to
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indicate where they apply: @sc{sfn} means the issues are only relevant to
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@ -6072,43 +6139,6 @@ $foo
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EOF
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@end example
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Many older shells (including the Bourne shell) implement here-documents
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inefficiently. Users can generally speed things up by using a faster
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shell, e.g., by using the command @samp{bash ./configure} rather than
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plain @samp{./configure}.
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Some shells can be extremely inefficient when there are a lot of
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here-documents inside a single statement. For instance if your
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@file{configure.ac} includes something like:
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@example
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@group
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if <cross_compiling>; then
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assume this and that
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else
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check this
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check that
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check something else
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on and on forever
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fi
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@end group
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@end example
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A shell parses the whole @code{if}/@code{fi} construct, creating
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temporary files for each here document in it. Some shells create links
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for such here-documents on every @code{fork ()}, so that the clean-up
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code they had installed correctly removes them. It is creating the
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links that the shell can take forever.
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Moving the tests out of the @code{if}/@code{fi}, or creating multiple
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@code{if}/@code{fi} constructs, would improve the performance
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significantly. Anyway, this kind of construct is not exactly the
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typical use of Autoconf. In fact, it's even not recommended, because M4
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macros can't look into shell conditionals, so we may fail to expand a
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macro when it was expanded before in a conditional path, and the
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condition turned out to be false at run-time, and we end up not
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executing the macro at all.
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@item @command{exit}
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@c -----------------
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