3 files changed, 70 insertions, 25 deletions
diff --git a/Completion/Unix/Command/_configure b/Completion/Unix/Command/_configure
index 3b22b53db..460144ac3 100644
--- a/Completion/Unix/Command/_configure
+++ b/Completion/Unix/Command/_configure
@@ -1,6 +1,11 @@
 #compdef configure config.status
 
-_arguments -- -i '(--(disable|enable)-FEATURE* --(with|without)-PACKAGE*)' \
+local ret=1
+local -a expl suf
+
+[[ -prefix - ]] ||
+    ! zstyle -T ":completion:${curcontext}:options" prefix-needed &&
+    _arguments -- -i '(--(disable|enable)-FEATURE* --(with|without)-PACKAGE*)' \
               -s '((#s)--disable- --enable-
 	           (#s)--enable- --disable-
 		   (#s)--with- --without-
@@ -8,4 +13,19 @@ _arguments -- -i '(--(disable|enable)-FEATURE* --(with|without)-PACKAGE*)' \
 	      '*=(E|)PREFIX*:prefix directory:_files -/' \
               '*=PROGRAM*:program:_command_names -e' \
 	      '*=NAME*executable*:program:_command_names -e' \
-	      '*=NAME*:file:_files'
+	      '*=NAME*:file:_files' && ret=0
+
+if [[ ! -prefix - ]]; then
+  if [[ "$PREFIX" = *\=* ]]; then
+    compstate[parameter]="${PREFIX%%\=*}"
+    compset -P 1 '*='
+    _value && ret=0
+  else
+    compset -S '=*' || suf=( -S = )
+    _wanted -x variables expl variable compadd $suf \
+        CC CFLAGS CPP CPPFLAGS CXX CXXFLAGS DEFS ERLCFLAGS FCFLAGS \
+        FFLAGS GOFLAGS LDFLAGS LIBS OBJCFLAGS OBJCXXFLAGS && ret=0
+  fi
+fi
+
+return ret
diff --git a/Completion/Unix/Command/_gcc b/Completion/Unix/Command/_gcc
index 17b9aa133..cf1cf7efa 100644
--- a/Completion/Unix/Command/_gcc
+++ b/Completion/Unix/Command/_gcc
@@ -1,10 +1,18 @@
-#compdef gcc g++ cc c++ llvm-gcc llvm-g++ clang clang++ -value-,LDFLAGS,-default- -value-,CFLAGS,-default- -value-,CXXFLAGS,-default- -value-,CPPFLAGS,-default- -P gcc-* -P g++-* -P c++-*
+#compdef gcc g++ cc c++ llvm-gcc llvm-g++ clang clang++ -value-,LDFLAGS,-default- -value-,CFLAGS,-default- -value-,CXXFLAGS,-default- -value-,CPPFLAGS,-default- -value-,CC,-default- -value-,CXX,-default- -P gcc-* -P g++-* -P c++-*
 
 local curcontext="$curcontext" state line ret=1 expl i
 local -a args args2 warnings arch
 typeset -A opt_args
 
-if [[ "$service" = -value-* ]]; then
+if [[ "$service" = -value-,CC,* ]]; then
+  _description compilers expl compiler
+  compadd "$expl[@]" -M 'r:|-=* r:|=*' -k 'commands[(I)(clang|([ig]|sun|open)cc(|<->|-devel)|icx)]'
+  return
+elif [[ "$service" = -value-,CXX,* ]]; then
+  _description compilers expl compiler
+  compadd "$expl[@]" -M 'r:|-=* r:|=*' -k 'commands[(I)((clang|g)++(|<->|-devel)|(sun|open|)CC|icpx)]'
+  return
+elif [[ "$service" = -value-* ]]; then
   compset -q
   words=( fake "$words[@]" )
   (( CURRENT++ ))
diff --git a/Completion/Unix/Command/_shutdown b/Completion/Unix/Command/_shutdown
index ab98a4325..fdadd3b12 100644
--- a/Completion/Unix/Command/_shutdown
+++ b/Completion/Unix/Command/_shutdown
@@ -1,35 +1,39 @@
 #compdef shutdown
 
-local -a args
+local curcontext="$curcontext" variant="$OSTYPE" ret=1
+local -a state line args suffixes
 
-if [[ -d /run/systemd/system ]]; then
-  _arguments \
-    '--help[display usage information]' \
-    '(-H --halt)'{-H,--halt}'[halt the machine]' \
-    '(-P --poweroff -h)'{-P,--poweroff,-h}'[power-off the machine (default)]' \
-    '(-r --reboot)'{-r,--reboot}'[reboot the machine]' \
-    "(--no-wall)-k[don't shutdown, just write wall message]" \
-    "(-k)--no-wall[don't send a wall message]" \
-    '-c[cancel pending shutdown]' \
-    '1: :_guard "^-*" "time (now/hh\:mm/+mins)"' \
-    '*:warning message'
-  return
-fi
+[[ -d /run/systemd/system ]] && variant=systemd
 
-case $OSTYPE in
+case $variant in
+  systemd)
+    args=(
+      "(-k)--no-wall[don't send a wall message]"
+      '1: :->times'
+      '*:warning message'
+      + '(action)'
+      '(* : -)--help[display usage information]'
+      "(--no-wall)-k[don't shutdown, just write wall message]"
+      {-H,--halt}'[halt the machine]'
+      {-P,--poweroff,-h}'[power-off the machine (default)]'
+      {-r,--reboot}'[reboot the machine]'
+      '-c[cancel pending shutdown]'
+    )
+  ;;
   *bsd*|dragonfly*|linux*|darwin*)
     args=(
-      '-h[halt the system after shutdown]'
-      '-r[reboot the system]'
+      '(-p -r -c)-h[halt the system after shutdown]'
+      '(-p -h -c)-r[reboot the system]'
       '-k[kick everybody off]'
       '-n[prevent file system cache from being flushed]'
-      '1:time (hh\:mm/+mins):_phony now -- _guard "^-*" "time (hh\:mm/+mins)"' \
+      '1: :->times'
+      '(*)-[read warning message from standard input]' \
       '*:warning message'
     )
   ;|
   *bsd*|dragonfly*)
     args+=(
-      '-p[turn off power after shutdown]'
+      '(-h -r -c)-p[turn off power after shutdown]'
     )
   ;|
   (net|open)bsd*)
@@ -39,13 +43,14 @@ case $OSTYPE in
     )
   ;|
   freebsd*|dragonfly*)
+    suffixes=( s:seconds :m:minutes h:hours )
     args+=(
       '-o[execute halt or reboot instead of sending a signal to init]'
     )
   ;|
   freebsd<12->.*)
     args+=(
-      '-c[power cycle the system instead of halting if possible]'
+      '(-h -r -p)-c[power cycle the system instead of halting if possible]'
     )
   ;;
   netbsd*)
@@ -74,4 +79,16 @@ case $OSTYPE in
   ;;
 esac
 
-_arguments $args
+_arguments -C $args && ret=0
+
+if [[ -n $state ]]; then
+  if compset -P '+'; then
+    _numbers -u minutes "grace period" $suffixes
+  else
+    _alternative \
+      'relative-times:relative time:{ compadd "$expl[@]" -S "" +; compadd "$expl[@]" now }' \
+      'absolute-times: :_guard "^-*" "time ([yymmdd]hhmm)"' && ret=0
+  fi
+fi
+
+return ret