bin/find-unused-defines.sh

   1 #
   2 # This is a pretty brute-force approach. It takes several hours to run on a top-spec MacbookAir.
   3 # It also produces some false positives, so it requires careful examination and testing of the results.
   4 #
   5 # Algorithm Summary:
   6 #   First we find all #defines,
   7 #   then we search for each of them in turn,
   8 #   and if we find only one instance of a #define, we print it out.
   9 #
  10 # Algorithm Detail:
  11 # (1) find #defines, excluding the externals folder
  12 # (2) extract just the constant name from the search results
  13 # (3) trim blank lines
  14 # (4) sort the results, mostly so I have an idea how far along the process is
  15 # (5) for each result:
  16 #   (6) grep for the constant
  17 #   (7) use awk to to check if only one match for a given constant was found
  18 #   (8) if so, generate a sed command to remove the #define
  19 #
  20 git grep -P '^#define\s+\w+\s+\w' -- "[!e][!x][!t]*" \
  21   | cut -s -d ' ' -f 2 \
  22   | sed '/^$/d' \
  23   | sort \
  24   | xargs -Ixxx sh -c \
  25     "git grep -w 'xxx' | awk -f bin/find-unused-defines.awk -v p1=xxx && echo \"xxx\" 1>&2"
  26
  27