Remove "." from default @INC when default_inc_excludes_dot is set

Perl now provides a way to build perl without . in @INC by default. If you want
this feature, you can build with -Ddefault_inc_excludes_dot

Because the testing / make process for perl modules do not function well
with . missing from @INC, Perl now supports the environment variable
PERL_USE_UNSAFE_INC=1 which makes Perl behave as it previously did,
returning . to @INC in all child processes.

WARNING: PERL_USE_UNSAFE_INC has been provided during the perl 5.25 development
cycle and is not guaranteed to function in perl 5.26.

Update unit tests and default value files to work with the new %Config
variable "default_inc_excludes_dot"

1 files changed, 24 insertions, 0 deletions

diff --git a/Configure b/Configure
index 44920204aa..84a34bf597 100755
--- a/Configure
+++ b/Configure
@@ -937,6 +937,7 @@ d_wcstombs=''
 d_wcsxfrm=''
 d_wctomb=''
 d_writev=''
+default_inc_excludes_dot=''
 dlext=''
 bin_ELF=''
 cccdlflags=''
@@ -20625,6 +20626,28 @@ EOCP
 	;;
 esac
 
+: Include . in @INC
+$cat <<EOM
+
+Historically Perl has provided a final fallback of the current working
+directory '.' when searching for a library. This, however, can lead to
+problems when a Perl program which loads optional modules is called from
+a shared directory. This can lead to executing unexpected code.
+
+EOM
+
+case "$default_inc_excludes_dot" in
+    $define|true|[yY]*) dflt="n" ;;
+    *)                  dflt='y' ;;
+esac
+
+rp='Provide '.' in @INC by default? '
+. ./myread
+case "$ans" in
+    [nN]*|define) default_inc_excludes_dot="$define" ;;
+    *)            default_inc_excludes_dot="$undef"  ;;
+esac
+
 : Check what kind of inf/nan your system has
 $echo "Checking the kind of infinities and nans you have..." >&4
 $echo "(The following tests may crash.  That's okay.)" >&4
@@ -24913,6 +24936,7 @@ db_prefixtype='$db_prefixtype'
 db_version_major='$db_version_major'
 db_version_minor='$db_version_minor'
 db_version_patch='$db_version_patch'
+default_inc_excludes_dot='$default_inc_excludes_dot'
 direntrytype='$direntrytype'
 dlext='$dlext'
 dlsrc='$dlsrc'