[PATCH] build: report an error message when missing test name

[Yann Droneaud]

Running "make test" without a test name fails with a surprising
unhelpful error message:

  $ make test
  make -r PARALLELMFLAGS="" -C .. objdir=`pwd` test
  make[1]: Entering directory '.../glibc'
  make subdir= -C  ..=../ .../glibc/build/.out
  make[2]: Entering directory '.../glibc'
  make[2]: *** ..=../: No such file or directory.  Stop.
  make[2]: Leaving directory '.../glibc'
  make[1]: *** [Makefile:743: test] Error 2
  make[1]: Leaving directory '.../glibc'
  make: *** [Makefile:9: test] Error 2

It's better to report a useful error message:

  $ make test
  make -r PARALLELMFLAGS="" -C .. objdir=`pwd` test
  make[1]: Entering directory '/home/ydroneaud/src/UPSTREAM/glibc'
  Makefile:742: *** Missing test name: usage make test t=<test name>.  Stop.
  make[1]: Leaving directory '/home/ydroneaud/src/UPSTREAM/glibc'
  make: *** [Makefile:9: test] Error 2
---
 Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Makefile b/Makefile
index 179dd478ffa8..a4a7b3aae1b8 100644
--- a/Makefile
+++ b/Makefile
@@ -739,6 +739,7 @@ iconvdata/% localedata/% po/%: FORCE
 # Example: make test t=wcsmbs/test-wcsnlen
 .PHONY: test
 test :
+	@$(if $t,:,$(error Missing test name: usage make test t=<test name>))
 	@-rm -f $(objpfx)$t.out
 	$(MAKE) subdir=$(patsubst %/,%,$(dir $t)) -C $(dir $t) ..=../ $(objpfx)$t.out
 	@cat $(objpfx)$t.test-result
-- 
2.34.1