ax_compare_version

This macro compares two version strings. It is used heavily in the macro _AX_PATH_BDB for library checking. Due to the various number of minor-version numbers that can exist, and the fact that string comparisons are not compatible with numeric comparisons, this is not necessarily trivial to do in a autoconf script. This macro makes doing these comparisons easy.

The six basic comparisons are available, as well as checking equality limited to a certain number of minor-version levels.

The operator OP determines what type of comparison to do, and can be one of:

  eq  - equal (test A == B)
  ne  - not equal (test A != B)
  le  - less than or equal (test A <= B)
  ge  - greater than or equal (test A >= B)
  lt  - less than (test A < B)
  gt  - greater than (test A > B)

Additionally, the eq and ne operator can have a number after it to limit the test to that number of minor versions.

  eq0 - equal up to the length of the shorter version
  ne0 - not equal up to the length of the shorter version
  eqN - equal up to N sub-version levels
  neN - not equal up to N sub-version levels

When the condition is true, shell commands ACTION-IF-TRUE are run, otherwise shell commands ACTION-IF-FALSE are run. The environment variable 'ax_compare_version' is always set to either 'true' or 'false' as well.

Examples:

   AX_COMPARE_VERSION([3.15.7],[lt],[3.15.8])
   AX_COMPARE_VERSION([3.15],[lt],[3.15.8])

would both be true.

   AX_COMPARE_VERSION([3.15.7],[eq],[3.15.8])
   AX_COMPARE_VERSION([3.15],[gt],[3.15.8])

would both be false.

   AX_COMPARE_VERSION([3.15.7],[eq2],[3.15.8])

would be true because it is only comparing two minor versions.

   AX_COMPARE_VERSION([3.15.7],[eq0],[3.15])

would be true because it is only comparing the lesser number of minor versions of the two values.

Note: The characters that separate the version numbers do not matter. An empty string is the same as version 0. OP is evaluated by autoconf, not configure, so must be a string, not a variable.

The author would like to acknowledge Guido Draheim whose advice about the m4_case and m4_ifvaln functions make this macro only include the portions necessary to perform the specific comparison specified by the OP argument in the final configure script.

dnl #########################################################################
AC_DEFUN([AX_COMPARE_VERSION], [
  # Used to indicate true or false condition
  ax_compare_version=false

  # Convert the two version strings to be compared into a format that
  # allows a simple string comparison.  The end result is that a version
  # string of the form 1.12.5-r617 will be converted to the form
  # 0001001200050617.  In other words, each number is zero padded to four
  # digits, and non digits are removed.
  AS_VAR_PUSHDEF([A],[ax_compare_version_A])
  A=`echo "$1" | sed -e 's/\([[0-9]]*\)/Z\1Z/g' \
                     -e 's/Z\([[0-9]]\)Z/Z0\1Z/g' \
                     -e 's/Z\([[0-9]][[0-9]]\)Z/Z0\1Z/g' \
                     -e 's/Z\([[0-9]][[0-9]][[0-9]]\)Z/Z0\1Z/g' \
                     -e 's/[[^0-9]]//g'`

  AS_VAR_PUSHDEF([B],[ax_compare_version_B])
  B=`echo "$3" | sed -e 's/\([[0-9]]*\)/Z\1Z/g' \
                     -e 's/Z\([[0-9]]\)Z/Z0\1Z/g' \
                     -e 's/Z\([[0-9]][[0-9]]\)Z/Z0\1Z/g' \
                     -e 's/Z\([[0-9]][[0-9]][[0-9]]\)Z/Z0\1Z/g' \
                     -e 's/[[^0-9]]//g'`

  dnl # In the case of le, ge, lt, and gt, the strings are sorted as necessary
  dnl # then the first line is used to determine if the condition is true.
  dnl # The sed right after the echo is to remove any indented white space.
  m4_case(m4_tolower($2),
  [lt],[
    ax_compare_version=`echo "x$A
x$B" | sed 's/^ *//' | sort -r | sed "s/x${A}/false/;s/x${B}/true/;1q"`
  ],
  [gt],[
    ax_compare_version=`echo "x$A
x$B" | sed 's/^ *//' | sort | sed "s/x${A}/false/;s/x${B}/true/;1q"`
  ],
  [le],[
    ax_compare_version=`echo "x$A
x$B" | sed 's/^ *//' | sort | sed "s/x${A}/true/;s/x${B}/false/;1q"`
  ],
  [ge],[
    ax_compare_version=`echo "x$A
x$B" | sed 's/^ *//' | sort -r | sed "s/x${A}/true/;s/x${B}/false/;1q"`
  ],[
    dnl Split the operator from the subversion count if present.
    m4_bmatch(m4_substr($2,2),
    [0],[
      # A count of zero means use the length of the shorter version.
      # Determine the number of characters in A and B.
      ax_compare_version_len_A=`echo "$A" | awk '{print(length)}'`
      ax_compare_version_len_B=`echo "$B" | awk '{print(length)}'`

      # Set A to no more than B's length and B to no more than A's length.
      A=`echo "$A" | sed "s/\(.\{$ax_compare_version_len_B\}\).*/\1/"`
      B=`echo "$B" | sed "s/\(.\{$ax_compare_version_len_A\}\).*/\1/"`
    ],
    [[0-9]+],[
      # A count greater than zero means use only that many subversions
      A=`echo "$A" | sed "s/\(\([[0-9]]\{4\}\)\{m4_substr($2,2)\}\).*/\1/"`
      B=`echo "$B" | sed "s/\(\([[0-9]]\{4\}\)\{m4_substr($2,2)\}\).*/\1/"`
    ],
    [.+],[
      AC_WARNING(
        [illegal OP numeric parameter: $2])
    ],[])

    # Pad zeros at end of numbers to make same length.
    ax_compare_version_tmp_A="$A`echo $B | sed 's/./0/g'`"
    B="$B`echo $A | sed 's/./0/g'`"
    A="$ax_compare_version_tmp_A"

    # Check for equality or inequality as necessary.
    m4_case(m4_tolower(m4_substr($2,0,2)),
    [eq],[
      test "x$A" = "x$B" && ax_compare_version=true
    ],
    [ne],[
      test "x$A" != "x$B" && ax_compare_version=true
    ],[
      AC_WARNING([illegal OP parameter: $2])
    ])
  ])

  AS_VAR_POPDEF([A])dnl
  AS_VAR_POPDEF([B])dnl

  dnl # Execute ACTION-IF-TRUE / ACTION-IF-FALSE.
  if test "$ax_compare_version" = "true" ; then
    m4_ifvaln([$4],[$4],[:])dnl
    m4_ifvaln([$5],[else $5])dnl
  fi
]) dnl AX_COMPARE_VERSION