#! /bin/sh
# use-before-set - find some uses of shell vars before setting them

# Copyright (C) 2005
# Ralf Wildenhues <address@hidden>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.

# This script assumes GNU sed, and mostly POSIX shell.

# TODO: parse multiple assignments per line
# TODO: parse multiple for loops per line (or don't)
# TODO: parse ${foo:=bar} (not portable, so no issue in configure scripts)
#
# NOTE: This script does not understand 'eval', nor does it follow
#       "interesting" quotation or escaping mechanisms.
# NOTE: This script has no idea of shell functions or any other
#       nonlinear execution paths.  Use `sh -u'.


# Set this to '#' if you want the second sed script
# to see single-quoted content.  (You do, trust me.)
skip_single_quoted='#'

# Ignore these variables, they are user-provided.
# Note: separate with spaces, no newlines in here!
skip_vars="SHELL CPPFLAGS LDFLAGS"

# These variables are user-provided; it's ok to use them
# provided the first use looks like the Autoconf-precious-vars test.
# Note: separate with spaces, no newlines in here!
precious_vars="\
CC CPP CFLAGS CXX CXXCPP CXXFLAGS CXXCPPFLAGS LD LDCXX LIBS \
F77 FFLAGS FC FCFLAGS GCJ GCJFLAGS RC \
AWK EGREP GREP INSTALL MAKE \
AR AS DLLTOOL NM OBJDUMP RANLIB STRIP"


### should not need to modify anything below this line ###

# fail on first error
set -e
set -u

# we rely on ASCII sorting; and please: make it fast
LC_ALL=C
export LC_ALL

if test $# -lt 1
then
  echo >&2 "usage: $0 script-to-check"
  exit 1
fi

last_param=
# Find all probable assignments,
# pair them up with corresponding line numbers.
# sort the resulting list by parameter name, then line
# (in order to pick only the first one later).
sed -n < "$1" '
# skip comments
/^[ 	]*#/b next
# parse "foo=bar"
/[a-zA-Z_][a-zA-Z_0-9]*=/ {
	s/.*[^a-zA-Z_]\([a-zA-Z_][a-zA-Z_0-9]*\)=.*/\1/
	s/^\([a-zA-Z_][a-zA-Z_0-9]*\)=.*/\1/
	p;=
}
# parse for loop variable assignment
/\<for[ 	][ 	]*[a-zA-Z_][a-zA-Z_0-9]*\([ 	][	]*in\|$\)/ {
	s/.*for[ 	][ 	]*\([a-zA-Z_][a-zA-Z_0-9]*\).*/\1/
	p;=
}
# parse read variable assignments
/\<read[ 	][ 	]*[a-zA-Z_]/ {
	s/.*read[ 	][ 	]*\([a-zA-Z_]\)/\1/
	T
	:read
	h
	s/\([a-zA-Z_][a-zA-Z_0-9]*\).*/\1/
	p
	=
	T
	x
	s/[a-zA-Z_][a-zA-Z_0-9]*[ 	][ 	]*//
	t read
}
:next
' |
sed 'N;s/\n/ /' |
sort -s -k1,1 -k2,2n |
while read param line
do
  if test "$param" = "$last_param"; then continue; fi
  last_param=$param
  case " $skip_vars " in (*" $param "*) continue;; esac
  case " $precious_vars " in
    (*" $param "*) skip_precious= ;;
    (*)            skip_precious='#' ;;
  esac
  prevline=`expr $line - 1`

  # Now, find any probable use of the variable before the assignment.
  sed -n < "$1" "
# end at the line before the assignment
${prevline} q
# skip comments
/^[ 	]*#/ b
# if desired, skip single quoted areas
${skip_single_quoted} s/'[^']*'//g
# find parameter expansion
/\(\\\$$param\>\)\|\(\\\${#\{0,1\}$param[#%+-:}]\)/ {
	# for precious variables: end searching without error,
	# when the specific autoconf snippet is found
	${skip_precious} /\<if test -[nz] \"\\\$$param\"; then/ q
	# autoconf cache variable test idiom:
	/\\\${$param+set}/ b
	# ok, we have a possible bug.
	i\
ERROR: $param used before set at line
	=
	p
}
" | sed 'N;N;s/\n/ /'

done
# vi:set sw=2: