configure: ${#param} must be supported by the shell for the testsuite

This will be required at least by the Automake-NG branch.

* configure.ac: Require the $AM_TEST_RUNNER_SHELL supports ${#param} as
a way to obtain the length of the expansion of the variable $param.

Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>

diff --git a/configure.ac b/configure.ac
index d49da6c61ea458fe5ec8bc5b14472b1d5272a971..a8db0614ea8d5ed6e450e58b5ba282f09445a7d3 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -296,6 +296,14 @@ AC_DEFUN([_AM_CHECK_CANDIDATE_SHELL],
       [test $((1 + 2 * 3)) = 7],
       [], [am_score=1; break])
 
+    _AM_CHECK_SHELL_FEATURE([$1],
+      [supports \${@%:@var}],
+      [zero='' one='x' twelve=' foobar baz!' \
+        && test ${@%:@zero} -eq 0 \
+        && test ${@%:@one} -eq 1 \
+        && test ${@%:@twelve} -eq 12],
+      [], [am_score=1; break])
+
     _AM_CHECK_SHELL_FEATURE([$1],
       [supports \${var@%:@glob} and \${var%glob}],
       [v=a/b/c \