1 files changed, 32 insertions, 0 deletions
diff --git a/unit-tests/job-output-long-lines.mk b/unit-tests/job-output-long-lines.mk
new file mode 100644
index 0000000000000..5a83bde0da3a7
--- /dev/null
+++ b/unit-tests/job-output-long-lines.mk
@@ -0,0 +1,32 @@
+# $NetBSD: job-output-long-lines.mk,v 1.4 2020/11/01 17:29:13 rillig Exp $
+#
+# The jobs may produce long lines of output.  A practical case are the echoed
+# command lines from compiler invocations, with their many -D options.
+#
+# Each of these lines must be written atomically to the actual output.
+# The markers for switching jobs must always be written at the beginning of
+# the line, to make them clearly visible in large log files.
+#
+# As of 2020-09-27, the default job buffer size is 1024.  When a job produces
+# output lines that are longer than this buffer size, these output pieces are
+# not terminated by a newline.  Because of this missing newline, the job
+# markers "--- job-a ---" and "--- job-b ---" are not always written at the
+# beginning of a line, even though this is expected by anyone reading the log
+# files.
+
+.MAKEFLAGS: -j2
+
+100:=	${:U1:S,1,2222222222,g:S,2,3333333333,g}
+5000:=	${100:S,3,4444444444,g:S,4,xxxxx,g}
+
+all: job-a job-b
+
+job-a:
+.for i in ${:U:range=20}
+	@echo ${5000:S,x,a,g}
+.endfor
+
+job-b:
+.for i in ${:U:range=20}
+	@echo ${5000:S,x,b,g}
+.endfor