Info Catalog m4: Errprint m4: Miscellaneous m4: M4exit

m4: Location

 
 14.2 Printing current location
 ==============================
 
 To make it possible to specify the location of an error, three utility
 builtins exist:
 
  -- Builtin: __file__
  -- Builtin: __line__
  -- Builtin: __program__
      Expand to the quoted name of the current input file, the current
      input line number in that file, and the quoted name of the current
      invocation of 'm4'.
 
      errprint(__program__:__file__:__line__: `input error
      ')
      error->m4:stdin:1: input error
      =>
 
    Line numbers start at 1 for each file.  If the file was found due to
 the '-I' option or 'M4PATH' environment variable, that is reflected in
DONTPRINTYET  the file name.  The syncline option ('-s', ⇒Invoking m4
 Preprocessor features.), and the 'f' and 'l' flags of 'debugmode' (*noteDONTPRINTYET  the file name.  The syncline option ('-s', ⇒Invoking m4
 Preprocessor features.), and the 'f' and 'l' flags of 'debugmode' (⇒
 Debug Levels), also use this notion of current file and line.
 Redefining the three location macros has no effect on syncline, debug,
 warning, or error message output.
 
 Include::):
 
      $ m4 -I examples
      define(`foo', ``$0' called at __file__:__line__')
      =>
      foo
      =>foo called at stdin:2
      include(`incl.m4')
      =>Include file start
      =>foo called at examples/incl.m4:2
      =>Include file end
      =>
 
    The location of macros invoked during the rescanning of macro
 expansion text corresponds to the location in the file where the
 expansion was triggered, regardless of how many newline characters the
 expansion text contains.  As of GNU M4 1.4.8, the location of text
 wrapped with 'm4wrap' (⇒M4wrap) is the point at which the
 'm4wrap' was invoked.  Previous versions, however, behaved as though
 wrapped text came from line 0 of the file "".
 
      define(`echo', `$@')
      =>
      define(`foo', `echo(__line__
      __line__)')
      =>
      echo(__line__
      __line__)
      =>4
      =>5
      m4wrap(`foo
      ')
      =>
      foo(errprint(__line__
      __line__
      ))
      error->8
      error->9
      =>8
      =>8
      __line__
      =>11
      m4wrap(`__line__
      ')
      =>
      ^D
      =>12
      =>6
      =>6
 
    The '__program__' macro behaves like '$0' in shell terminology.  If
 you invoke 'm4' through an absolute path or a link with a different
 spelling, rather than by relying on a 'PATH' search for plain 'm4', it
 will affect how '__program__' expands.  The intent is that you can use
 it to produce error messages with the same formatting that 'm4' produces
 internally.  It can also be used within 'syscmd' (⇒Syscmd) to
 pick the same version of 'm4' that is currently running, rather than
 whatever version of 'm4' happens to be first in 'PATH'.  It was first
 introduced in GNU M4 1.4.6.
 

Info Catalog m4: Errprint m4: Miscellaneous m4: M4exit