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      1 # $NetBSD: depsrc-ignore.mk,v 1.5 2020/11/15 20:20:58 rillig Exp $
      2 #
      3 # Tests for the special source .IGNORE in dependency declarations,
      4 # which ignores any command failures for that target.
      5 #
      6 # Even though 'ignore-errors' fails, 'all' is still made.  Since 'all' is
      7 # not marked with .IGNORE, it stops at the first failing command.
      8 #
      9 # XXX: The ordering of the messages in the output is confusing.
     10 # The "ignored" comes much too late to be related to the "false
     11 # ignore-errors".  This is due to stdout being buffered.
     12 #
     13 # The "continuing" message comes from the -k option.  If there had been
     14 # other targets independent of "all", these would be built as well.
     15 #
     16 # Enabling the debugging option -de changes the order in which the messages
     17 # appear.  Now the "ignored" message is issued in the correct position.
     18 # The explanation for the output reordering is that the output is buffered.
     19 # As the manual page says, in debugging mode stdout is line buffered.
     20 # In these tests the output is redirected to a file, therefore stdout is
     21 # fully buffered.
     22 #
     23 # This is what actually happens, as of 2020-08-29.  To verify it, set the
     24 # following breakpoints in CompatRunCommand:
     25 #
     26 # * the "!silent" line, to see all commands
     27 # * the "fflush" line, to see stdout being flushed
     28 # * the "status = WEXITSTATUS" line
     29 # * the "(continuing)" line
     30 # * the "(ignored)" line
     31 #
     32 # The breakpoints are visited in the following order:
     33 #
     34 # "ignore-errors begin"
     35 #	Goes directly to STDOUT_FILENO since it is run in a child process.
     36 # "false ignore-errors"
     37 #	Goes to the stdout buffer (CompatRunCommand, keyword "!silent") and
     38 #	the immediate call to fflush(stdout) copies it to STDOUT_FILENO.
     39 # "*** Error code 1 (ignored)"
     40 #	Goes to the stdout buffer but is not flushed (CompatRunCommand, near
     41 #	the end).
     42 # "ignore-errors end"
     43 #	Goes directly to STDOUT_FILENO.
     44 # "all begin"
     45 #	Goes directly to STDOUT_FILENO.
     46 # "false all"
     47 #	Goes to the stdout buffer, where the "*** Error code 1 (ignored)" is
     48 #	still waiting to be flushed.  These two lines are flushed now.
     49 # "*** Error code 1 (continuing)"
     50 #	Goes to the stdout buffer.
     51 # "Stop."
     52 #	Goes to the stdout buffer.
     53 # exit(1)
     54 #	Flushes the stdout buffer to STDOUT_FILENO.
     55 
     56 all: ignore-errors
     57 
     58 ignore-errors: .IGNORE
     59 	@echo $@ begin
     60 	false $@
     61 	@echo $@ end
     62 
     63 all:
     64 	@echo $@ begin
     65 	false $@
     66 	@echo $@ end
     67