Re: [patch] Avoid some of the sc_ rules to freeze

[jemarch]

   Would it be better to just add /dev/null as a parameter to grep?
   I.E. like:

           @grep -nE 'error \(EXIT_SUCCESS,'                            \
               $$($(VC_LIST_EXCEPT) /dev/null | grep -E '\.[chly]$$')&& \
             { echo '$(ME): found error (EXIT_SUCCESS' 1>&2; exit 1; } || :


The grep freezing is the top-level one, not the one matching the
.[chly] files.  It would be:

 @grep -nE 'error \(EXIT_SUCCESS,'                                    \
    $$($(VC_LIST_EXCEPT) | grep -E '\.[chly]$$') < /dev/null  &&      \
       { echo '$(ME): found error (EXIT_SUCCESS' 1>&2; exit 1; } || :

But consider the sc_ rules that are searching files not containing a
given pattern:

sc_program_name:
        files=$$(grep -l '^main *(' $$($(VC_LIST_EXCEPT) | grep '\.c$$'));      
\
        grep -LE 'set_program_name *\(m?argv\[0\]\);' $$files < /dev/null       
\
              | grep . &&                                                       
\
          { echo '$(ME): the above files do not call set_program_name'          
\
                1>&2; exit 1; } || :;

In that case the grep uses the -L option, and the effect of using the
redirection from /dev/null is:

$ make sc_program_name
program_name
(standard input)

I suggest to use the following solution that works properly in all
cases while avoiding the code duplication (in the spirit of
_prohibit_regexp):

define _sc_maybe_matching_files
  dummy=; : so we do not need a semicolon before each use;             \
  test "x$$re" != x || { echo '$(ME): re not defined' 1>&2; exit 1; }; \
  if test -n "$$matching"; then matching='yes'; fi        \
  files=$$($(VC_LIST_EXCEPT) | grep -E "$$fre");          \
  if test -n "$$files"; then                              \
    if test "$$matching" = "yes"; then                    \
       grep -nE "$$re" $$files &&                         \
          {echo "$(ME): $$msg" 1>&2; exit 1; } || :       \
    else                                                  \
       grep -LE "$$re" $$files | grep . &&                \
          {echo "$(ME): $$msg" 1>&2; exit1: } || :        \
  else :;                                                 \
  fi
endef

define _sc_matching_files
  matching='yes'                                          \
  $(_sc_maybe_matching_files)
endef

define _sc_non_matching_files                             \
  matching='no'                                           \
  $(_sc_maybe_matching_files)
endef

sc_error_exit_success:
        @fre='\.[chly]$$'                                 \
        re='error \(EXIT_SUCCESS,'                        \
        msg='$(ME): found error (EXIT_SUCCESS'            \
          $(_sc_matching_files)

sc_program_name:
        @fre='\.c$$'                                      \
        re='set_program_name *\(m?argv\[0\]\);'           \
        msg='$(ME): the above files do not call set_program_name' \
          $(_sc_non_matching_files)
        
...