From 6e1ee078ccaa11479cd90c386198b84f94a18f72 Mon Sep 17 00:00:00 2001
From: Julian Ospald <hasufell@posteo.de>
Date: Thu, 18 Apr 2019 11:36:59 +0800
Subject: [PATCH 1/2] posix_realpath: make sure we don't loop infinitely

On broken symlink loops this would never terminate. The most
naive and easy solution is a max of loop steps.
---
 ghcup | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/ghcup b/ghcup
index 1d1a9e6..6ccb855 100755
--- a/ghcup
+++ b/ghcup
@@ -1131,12 +1131,20 @@ get_distro_alias() {
 # @STDOUT: realpath of the given file
 posix_realpath() {
     [ -z "$1" ] && die "Internal error: no argument given to posix_realpath"
+    current_loop=0
+    max_loops=50
     mysource=$1
 
     while [ -h "${mysource}" ]; do
+        current_loop=$((current_loop+1))
         mydir="$( cd -P "$( dirname "${mysource}" )" > /dev/null 2>&1 && pwd )"
         mysource="$(readlink "${mysource}")"
         [ "${mysource%${mysource#?}}"x != '/x' ] && mysource="${mydir}/${mysource}"
+
+        if [ ${current_loop} -gt ${max_loops} ] ; then
+            (>&2 echo "${1}: Too many levels of symbolic links")
+            break
+        fi
     done
     mydir="$( cd -P "$( dirname "${mysource}" )" > /dev/null 2>&1 && pwd )"
 
@@ -1149,7 +1157,7 @@ posix_realpath() {
         echo "${mydir%/}/$(basename "${mysource}")"
     fi
 
-    unset mysource mydir posix_realpath_error
+    unset current_loop max_loops mysource mydir
 }
 
 

From 17aafe343961bbb73658a0f55c1ab1d1624e423e Mon Sep 17 00:00:00 2001
From: Julian Ospald <hasufell@posteo.de>
Date: Thu, 18 Apr 2019 11:37:42 +0800
Subject: [PATCH 2/2] posix_realpath: if dir does not exist also append to
 current dir

This matches realpath behavior.
---
 ghcup | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/ghcup b/ghcup
index 6ccb855..df1b215 100755
--- a/ghcup
+++ b/ghcup
@@ -1127,7 +1127,7 @@ get_distro_alias() {
 #   and
 #   https://stackoverflow.com/a/246128
 #
-# If the file does not exist, just prints the argument unchanged.
+# If the file does not exist, just prints it appended to the current directory.
 # @STDOUT: realpath of the given file
 posix_realpath() {
     [ -z "$1" ] && die "Internal error: no argument given to posix_realpath"
@@ -1151,8 +1151,6 @@ posix_realpath() {
     # TODO: better distinguish between "does not exist" and "permission denied"
     if [ -z "${mydir}" ] ; then
         (>&2 echo "${1}: Permission denied")
-    elif [ ! -e "$1" ] ; then
-        echo "${mysource}"
     else
         echo "${mydir%/}/$(basename "${mysource}")"
     fi