From 4d3db9a78fb84f837a0b1665906ce0da1856a3e3 Mon Sep 17 00:00:00 2001
From: Pedram Ashofteh Ardakani <pedramardakani@gmail.com>
Date: Thu, 23 Apr 2020 17:34:33 +0430
Subject: Configure.sh: build directory checked for ability to modify
 permissions

Until now we only checked for the existance and write-ability of the build
directory. But we recently discovered that if the specified build-directory
is in a non-POSIX compatible partition (for example NTFS), permissions
can't be modified and this can cause crashs in some programs (in
particular, while building Perl, see [1]). The thing that makes this
problem hard to identify is that on such partitions, `chmod' will still
return 0 (so it was hard to find).

With this commit, a check has been added after the user specifies the
build-directory. If the proposed build directory is not able to handle
permissions as expected, the configure script will not continue and will
let the user know and will ask them for another directory.

Also, the two printed characters at the start of error messages were
changed to `**' (instead of `--'). When everything is good, we'll use `--'
to tell the user that their given directory will be used as the build
directory. And since there are multiple checks now, the final message to
specify a new build directory is now moved to the end and not repeated in
every check.

[1] https://savannah.nongnu.org/support/?110220
---
 reproduce/software/shell/configure.sh | 92 ++++++++++++++++++++++++++++++-----
 1 file changed, 81 insertions(+), 11 deletions(-)

diff --git a/reproduce/software/shell/configure.sh b/reproduce/software/shell/configure.sh
index b4cf43b..dd3b9bc 100755
--- a/reproduce/software/shell/configure.sh
+++ b/reproduce/software/shell/configure.sh
@@ -93,6 +93,64 @@ absolute_dir ()
 
 
 
+# Check file permission handling (POSIX-compatibility)
+# ----------------------------------------------------
+#
+# Check if a `given' directory handles permissions as expected.
+#
+# This is to prevent a known bug in the NTFS filesystem that prevents
+# proper installation of Perl, and probably some other packages. This
+# function receives the directory as an argument and then, creates a dummy
+# file, and examines whether the given directory handles the file
+# permissions as expected.
+#
+# Returns `0' if everything is fine, and `255' otherwise. Choosing `0' is
+# to mimic the `$ echo $?' behavior, while choosing `255' is to prevent
+# misunderstanding 0 and 1 as true and false.
+#
+# ===== CAUTION! ===== #
+#
+# Since there is a `set -e' before running this function, the whole script
+# stops and exits IF the `check_permission' (or any other function) returns
+# anything OTHER than `0'! So, only use this function as a test. Here's a
+# minimal example:
+#
+#     if $(check_permission $some_directory) ; then
+#       echo "yay"; else "nay";
+#     fi ;
+check_permission ()
+{
+    # Make a `junk' file, activate its executable flag and record its
+    # permissions generally.
+    local junkfile=$1/check_permission_tmp_file
+    rm -f $junkfile
+    echo "Don't let my short life go to waste" > $junkfile
+    chmod +x $junkfile
+    local perm_before=$(ls -l $junkfile | awk '{print $1}')
+
+    # Now, remove the executable flag and record the permissions.
+    chmod -x $junkfile
+    local perm_after=$(ls -l $junkfile | awk '{print $1}')
+
+    # Clean up before leaving the function
+    rm -f $junkfile
+
+    # If the permissions are equal, the filesystem doesn't allow
+    # permissions.
+    if [ $perm_before = $perm_after ]; then
+        # Setting permission FAILED
+        return 1
+    else
+        # Setting permission SUCCESSFUL
+	return 0
+    fi
+}
+
+
+
+
+
+
 # Check for C/C++ compilers
 # -------------------------
 #
@@ -653,21 +711,20 @@ EOF
                 bdir=$(absolute_dir $build_dir)
                 rm -rf $build_dir/$junkname
             else
-                echo " -- Can't write in '$build_dir'"; echo
+                echo " ** Can't write in '$build_dir'"; echo
             fi
         else
             if mkdir $build_dir 2> /dev/null; then
                 instring="the newly created"
                 bdir=$(absolute_dir $build_dir)
             else
-                echo " -- Can't create '$build_dir'"; echo
+                echo " ** Can't create '$build_dir'"; echo
             fi
         fi
 
         # If its given, make sure it isn't a subdirectory of the source
         # directory.
         if ! [ x"$bdir" = x ]; then
-            echo "Given build directory: $bdir"
             if echo "$bdir/" \
                     | grep '^'$currentdir 2> /dev/null > /dev/null; then
 
@@ -676,17 +733,30 @@ EOF
 
                 # Inform the user that this is not acceptable and reset `bdir'.
                 bdir=
-                echo " -- The build-directory cannot be under the source-directory."
-                echo "    Please specify another build-directory that is outside of the source."
-                echo ""
-            else
-                echo " -- Build directory set to ($instring): '$bdir'"
+                echo " ** The build-directory cannot be under the source-directory."
+            fi
+        fi
+
+	# If everything is fine until now, see if we're able to manipulate
+	# file permissions.
+	if ! [ x"$bdir" = x ]; then
+            if ! $(check_permission $bdir); then
+                bdir=
+                echo " ** File permissions can't be modified in this directory"
             fi
         fi
 
-        # Reset `build_dir' to blank, so it continues asking when the
-        # previous value wasn't usable.
-        build_dir=
+        # If the build directory was good, the loop will stop, if not,
+        # reset `build_dir' to blank, so it continues asking for another
+        # directory and let the user know that they must select a new
+        # directory.
+        if [ x$bdir = x ]; then
+            build_dir=
+            echo " ** Please select another directory."
+            echo ""
+        else
+            echo " -- Build directory set to ($instring): '$bdir'"
+        fi
     done
 fi
 
-- 
cgit v1.2.1