For what it's worth, Autoconf does not assume that arithmetic
expansion will be available. Instead, it emits the following shell
code:
if ( eval 'test $(( 1 + 1 )) = 2' ) 2>/dev/null; then
eval 'func_arith ()
{
func_arith_result=$(( $* ))
}'
else
func_arith ()
{
func_arith_result=`expr "$@"`
}
fi
2017-12-17 23:55 GMT+01:00 Rodrigo Tobar <rtobar at icrar.org>:
Dear all,
During a recent package submission, we were highlighted that some lines in
our configure script didn't follow the correct syntax. The lines looked like
this:
x=$(($y/10))
We were indicated at the time that this is because the statement does not
use Bourne shell syntax, which is absolutely true, and also that the manual
warns about this, which is true again. So far everything is clear.
However, what confuses me is that even when the manual says that "you can
include an executable (Bourne) shell script configure in your package" [1],
the associated footnote says something slightly different: "The script
should only assume a POSIX-compliant /bin/sh" [2]. The footnote goes even
further, and links to the POSIX specification of the Shell Command Language
[3] (as published by The Open Group), which explicitly includes arithmetic
expressions like the one above in its syntax [4].
My question then is: what exact dialect should be considered? Given that the
statement above does not work in the Bourne shell, I conclude that the
Bourne shell is not POSIX-compliant. That in turn would make the manual
ambiguous as to the precise dialect that should be used by our configure
scripts, and either the shells used by R should be changed to be
POSIX-compliants, or the manual edited to be more precise regarding .
Many thanks.
Rodrigo
[1]
https://cran.r-project.org/doc/manuals/r-release/R-exts.html#Configure-and-cleanup
[2] https://cran.r-project.org/doc/manuals/r-release/R-exts.html#FOOT25
[3] http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html
[4]
http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_06_04