tests: Use variable redirections to dup std{out,err}

Previously, we hardcoded file descriptors 3 and 4 for duplicating
stdandard output/error respectively.  In preparation for keeping
inherited FDs open, switch to using bash's variable redirection feature
to dynamically assign FDs.

This feature is only available from bash 4.1 onwards, so this marks the
end of our support for bash 3.  macOS users will need to install a
modern bash version to run our tests.

1 files changed, 8 insertions, 9 deletions

diff --git a/tests/util.sh b/tests/util.sh
index 5bd3328..686cc77 100644
--- a/tests/util.sh
+++ b/tests/util.sh
@@ -68,7 +68,7 @@ stdenv() {
 
     # Close stdin so bfs doesn't think we're interactive
     # dup() the standard fds for logging even when redirected
-    exec </dev/null 3>&1 4>&2
+    exec </dev/null {DUPOUT}>&1 {DUPERR}>&2
 }
 
 # Drop root priviliges or bail
@@ -159,19 +159,18 @@ defer() {
 
 # Pop a single command from the defer stack and run it
 pop_defer() {
-    local i=$((${#DEFER_CMDS[@]} - 1))
-    local cmd="${DEFER_CMDS[$i]}"
-    local file="${DEFER_FILES[$i]}"
-    local line="${DEFER_LINES[$i]}"
-    unset "DEFER_CMDS[$i]"
-    unset "DEFER_FILES[$i]"
-    unset "DEFER_LINES[$i]"
+    local cmd="${DEFER_CMDS[-1]}"
+    local file="${DEFER_FILES[-1]}"
+    local line="${DEFER_LINES[-1]}"
+    unset "DEFER_CMDS[-1]"
+    unset "DEFER_FILES[-1]"
+    unset "DEFER_LINES[-1]"
 
     local ret=0
     eval "$cmd" || ret=$?
 
     if ((ret != 0)); then
-        debug "$file" $line "${RED}error $ret${RST}" "defer $cmd" >&4
+        debug "$file" $line "${RED}error $ret${RST}" "defer $cmd" >&$DUPERR
     fi
 
     return $ret