Autoconf. Generated configure file may use grep but does not unset the GREP_OPTIONS.

[Ilay Bobir]

Hi,

Starting with version 2.4 GNU grep supports specification of default 
option values via GREP_OPTIONS environment variable.  Many if not all of 
the configure files generated by the autoconf use grep.  For example, 
configure file for libtool uses grep.

If GREP_OPTIONS is set it may contain flags that will break configure as 
grep will behave in an unexpected fashion.  Doing

    unset GREP_OPTIONS

at the start of the configure file will fix the issue.

It is true that configure files are not the only scripts that will break 
if the GREP_OPTIONS is defined.  But configure files are quite 
widespread and if they break in the presence of the GREP_OPTIONS it 
makes this environment variable effectively unusable.

Please CC me as I am not subscribed to any of autoconf mailing lists.

Ilya Bobir