mirror/autoconf
2
0
Fork 0
mirror of git://git.sv.gnu.org/autoconf synced 2025-01-06 10:25:53 +08:00
Code Issues Packages Projects Releases Wiki Activity

docs: avoid use of $tmp outside of config.status use

Browse Source 
* doc/autoconf.texi (Polymorphic Variables, Shell Substitutions):
Use $var or $t instead.
(Limitations of Usual Tools): Use $dir instead.
(Initialization Macros) <AS_TMPDIR>: Make good on the NEWS
regarding AS_TMPDIR being documented as consuming $tmp.
Suggested by Ralf Wildenhues.

Signed-off-by: Eric Blake <eblake@redhat.com>
This commit is contained in:
Eric Blake 2010-08-27 12:55:54 -06:00
parent 838bdfa56d
commit 6284d1bef7
2 changed files with 51 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
ChangeLog
View File

@ -1,3 +1,13 @@
2010-08-30 Eric Blake <eblake@redhat.com>
docs: avoid use of $tmp outside of config.status use
* doc/autoconf.texi (Polymorphic Variables, Shell Substitutions):
Use $var or $t instead.
(Limitations of Usual Tools): Use $dir instead.
(Initialization Macros) <AS_TMPDIR>: Make good on the NEWS
regarding AS_TMPDIR being documented as consuming $tmp.
Suggested by Ralf Wildenhues.
2010-08-29 Paul Eggert <eggert@cs.ucla.edu>
AC_PROG_YACC: fix comment re what "yacc" stands for

55
doc/autoconf.texi
View File

@ -13442,8 +13442,8 @@ results in a script that will output the line @samp{hello} three times.
AC_DEFUN([MY_ACTION],
[AS_LITERAL_IF([$1],
[echo "$$1"],
[AS_VAR_COPY([tmp], [$1])
echo "$tmp"],
[AS_VAR_COPY([var], [$1])
echo "$var"],
[eval 'echo "$'"$1"\"])])
foo=bar bar=hello
MY_ACTION([bar])
@ -13462,8 +13462,8 @@ efficient scaling.
For situations where the final contents of @var{var} are relatively
short (less than 256 bytes), it is more efficient to use the simpler
code sequence of @code{@var{var}=$@{@var{var}@}@var{text}} (or its
polymorphic equivalent of @code{AS_VAR_COPY([tmp], [@var{var}])} and
@code{AS_VAR_SET([@var{var}], ["$tmp"@var{text}])}). But in the case
polymorphic equivalent of @code{AS_VAR_COPY([t], [@var{var}])} and
@code{AS_VAR_SET([@var{var}], ["$t"@var{text}])}). But in the case
when the script will be repeatedly appending text into @code{var},
issues of scaling start to become apparent. A naive implementation
requires execution time linear to the length of the current contents of
@ -13702,6 +13702,33 @@ script. This macro is automatically invoked by @code{AC_INIT} in
configure scripts.
@end defmac
@defmac AS_TMPDIR (@var{prefix}, @dvar{dir, $@{TMPDIR:=/tmp@}})
@asindex{TMPDIR}
@evindex TMPDIR
@ovindex tmp
Create, as safely as possible, a temporary sub-directory within
@var{dir} with a name starting with @var{prefix}. @var{prefix} should
be 2-4 characters, to make it slightly easier to identify the owner of
the directory. If @var{dir} is omitted, then the value of @env{TMPDIR}
will be used (defaulting to @samp{/tmp}). On success, the name of the
newly created directory is stored in the shell variable @code{tmp}. On
error, the script is aborted.
Typically, this macro is coupled with some exit traps to delete the created
directory and its contents on exit or interrupt. However, there is a
slight window between when the directory is created and when the name is
actually known to the shell, so an interrupt at the right moment might
leave the temporary directory behind. Hence it is important to use a
@var{prefix} that makes it easier to determine if a leftover temporary
directory from an interrupted script is safe to delete.
The use of the output variable @samp{$tmp} rather than something in the
@samp{as_} namespace is historical; it has the unfortunate consequence
that reusing this otherwise common name for any other purpose inside
your script has the potential to break any cleanup traps designed to
remove the temporary directory.
@end defmac
@defmac AS_SHELL_SANITIZE
@asindex{SHELL_SANITIZE}
Initialize the shell suitably for @command{configure} scripts. This has
@ -15475,15 +15502,15 @@ b c
Perhaps the easiest way to work around quoting issues in a manner
portable to all shells is to place the results in a temporary variable,
then use @samp{$tmp} as the @var{value}, rather than trying to inline
then use @samp{$t} as the @var{value}, rather than trying to inline
the expression needing quoting.
@example
$ @kbd{/bin/sh -c 'tmp="a b\"'\''@}\\"; echo "$@{a-$tmp@}"'}
$ @kbd{/bin/sh -c 't="a b\"'\''@}\\"; echo "$@{a-$t@}"'}
b c"'@}\
$ @kbd{ksh -c 'tmp="a b\"'\''@}\\"; echo "$@{a-$tmp@}"'}
$ @kbd{ksh -c 't="a b\"'\''@}\\"; echo "$@{a-$t@}"'}
b c"'@}\
$ @kbd{bash -c 'tmp="a b\"'\''@}\\"; echo "$@{a-$tmp@}"'}
$ @kbd{bash -c 't="a b\"'\''@}\\"; echo "$@{a-$t@}"'}
b c"'@}\
@end example
@ -18428,22 +18455,22 @@ use a file inside this directory. Both methods prevent attackers from
gaining control, though @command{mktemp} is far less likely to fail
gratuitously under attack.
Here is sample code to create a new temporary directory safely:
Here is sample code to create a new temporary directory @samp{$dir} safely:
@example
# Create a temporary directory $tmp in $TMPDIR (default /tmp).
# Create a temporary directory $dir in $TMPDIR (default /tmp).
# Use mktemp if possible; otherwise fall back on mkdir,
# with $RANDOM to make collisions less likely.
: "$@{TMPDIR:=/tmp@}"
@{
tmp=`
dir=`
(umask 077 && mktemp -d "$TMPDIR/fooXXXXXX") 2>/dev/null
` &&
test -n "$tmp" && test -d "$tmp"
test -d "$dir"
@} || @{
tmp=$TMPDIR/foo$$-$RANDOM
dir=$TMPDIR/foo$$-$RANDOM
@c $$ restore font-lock
(umask 077 && mkdir "$tmp")
(umask 077 && mkdir "$dir")
@} || exit $?
@end example