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docs: mention Solaris here-docs vs. ${a-"b c"}

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* doc/autoconf.texi (Shell Substitutions) <${var:=value}>:
Document problem of "" within here-docs.
Reported by Ralf Wildenhues.

Signed-off-by: Eric Blake <eblake@redhat.com>
This commit is contained in:
Eric Blake 2010-08-30 11:11:32 -06:00
parent 30378453ea
commit 2626155d5c
2 changed files with 29 additions and 2 deletions
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@ -1,5 +1,10 @@
2010-08-30 Eric Blake <eblake@redhat.com>
docs: mention Solaris here-docs vs. ${a-"b c"}
* doc/autoconf.texi (Shell Substitutions) <${var:=value}>:
Document problem of "" within here-docs.
Reported by Ralf Wildenhues.
fortran: always avoid AC_LANG_CONFTEST warning
* lib/autoconf/lang.m4 (AC_LANG_CONFTEST()): Make the default
match the fact that the default AC_LANG_SOURCE does not inline

26
doc/autoconf.texi
View File

@ -15466,7 +15466,8 @@ use null variable substitution patterns in configure scripts.
@cindex $@{@var{var}+@var{value}@}
When using @samp{$@{@var{var}-@var{value}@}} or
@samp{$@{@var{var}-@var{value}@}} for providing alternate substitutions,
@var{value} must either be a single shell word or be quoted. Solaris
@var{value} must either be a single shell word, quoted, or in the
context of an unquoted here-document. Solaris
@command{/bin/sh} complains otherwise.
@example
@ -15476,12 +15477,17 @@ $ @kbd{/bin/sh -c 'echo $@{a-'\''b c'\''@}'}
b c
$ @kbd{/bin/sh -c 'echo "$@{a-b c@}"'}
b c
$ @kbd{/bin/sh -c 'cat <<EOF
$@{a-b c@}
EOF}
b c
@end example
According to Posix, if an expansion occurs inside double quotes, then
the use of unquoted double quotes within @var{value} is unspecified, and
any single quotes become literal characters; in that case, escaping must
be done with backslash.
be done with backslash. Likewise, the use of unquoted here-documents is
a case where double quotes have unspecified results:
@example
$ @kbd{/bin/sh -c 'echo "$@{a-"b c"@}"'}
@ -15498,6 +15504,22 @@ $ @kbd{/bin/sh -c 'a=; echo "$@{a+\"b c\"@}"'}
"b c"
$ @kbd{/bin/sh -c 'a=; echo "$@{a+b c@}"'}
b c
$ @kbd{/bin/sh -c 'cat <<EOF
$@{a-"b c"@}
EOF'}
"b c"
$ @kbd{/bin/sh -c 'cat <<EOF
$@{a-'b c'@}
EOF'}
'b c'
$ @kbd{bash -c 'cat <<EOF
$@{a-"b c"@}
EOF'}
b c
$ @kbd{bash -c 'cat <<EOF
$@{a-'b c'@}
EOF'}
'b c'
@end example
Perhaps the easiest way to work around quoting issues in a manner