(make.info.gz) Errors

 
 5.5 Errors in Recipes
 =====================
 
 After each shell invocation returns, `make' looks at its exit status.
 If the shell completed successfully (the exit status is zero), the next
 line in the recipe is executed in a new shell; after the last line is
 finished, the rule is finished.
 
    If there is an error (the exit status is nonzero), `make' gives up on
 the current rule, and perhaps on all rules.
 
    Sometimes the failure of a certain recipe line does not indicate a
 problem.  For example, you may use the `mkdir' command to ensure that a
 directory exists.  If the directory already exists, `mkdir' will report
 an error, but you probably want `make' to continue regardless.
 
    To ignore errors in a recipe line, write a `-' at the beginning of
 the line's text (after the initial tab).  The `-' is discarded before
 the line is passed to the shell for execution.
 
    For example,
 
      clean:
              -rm -f *.o
 
 This causes `make' to continue even if `rm' is unable to remove a file.
 
    When you run `make' with the `-i' or `--ignore-errors' flag, errors
 are ignored in all recipes of all rules.  A rule in the makefile for
 the special target `.IGNORE' has the same effect, if there are no
 prerequisites.  These ways of ignoring errors are obsolete because `-'
 is more flexible.
 
    When errors are to be ignored, because of either a `-' or the `-i'
 flag, `make' treats an error return just like success, except that it
 prints out a message that tells you the status code the shell exited
 with, and says that the error has been ignored.
 
    When an error happens that `make' has not been told to ignore, it
 implies that the current target cannot be correctly remade, and neither
 can any other that depends on it either directly or indirectly.  No
 further recipes will be executed for these targets, since their
 preconditions have not been achieved.
 
    Normally `make' gives up immediately in this circumstance, returning
 a nonzero status.  However, if the `-k' or `--keep-going' flag is
 specified, `make' continues to consider the other prerequisites of the
 pending targets, remaking them if necessary, before it gives up and
 returns nonzero status.  For example, after an error in compiling one
 object file, `make -k' will continue compiling other object files even
 though it already knows that linking them will be impossible.  
 Summary of Options Options Summary.
 
    The usual behavior assumes that your purpose is to get the specified
 targets up to date; once `make' learns that this is impossible, it
 might as well report the failure immediately.  The `-k' option says
 that the real purpose is to test as many of the changes made in the
 program as possible, perhaps to find several independent problems so
 that you can correct them all before the next attempt to compile.  This
 is why Emacs' `compile' command passes the `-k' flag by default.  
 
    Usually when a recipe line fails, if it has changed the target file
 at all, the file is corrupted and cannot be used--or at least it is not
 completely updated.  Yet the file's time stamp says that it is now up to
 date, so the next time `make' runs, it will not try to update that
 file.  The situation is just the same as when the shell is killed by a
 signal;  Interrupts.  So generally the right thing to do is to
 delete the target file if the recipe fails after beginning to change
 the file.  `make' will do this if `.DELETE_ON_ERROR' appears as a
 target.  This is almost always what you want `make' to do, but it is
 not historical practice; so for compatibility, you must explicitly
 request it.
Info Catalog
(make.info.gz) Parallel
(make.info.gz) Recipes
(make.info.gz) Interrupts
automatically generated by info2html