maint: test bad format string crash.

* doc/m4.texi (Format): Add a test.

Signed-off-by: Eric Blake <eblake@redhat.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/doc/m4.texi b/doc/m4.texi
index 5a31eec8..bc2fccaf 100644
--- a/doc/m4.texi
+++ b/doc/m4.texi
@@ -7522,6 +7522,18 @@ format(`%.1f', `2a')
 @result{}2.0
 @end example
 
+@ignore
+@comment Expose a crash with a bad format string fixed in 1.4.15.
+@comment Unfortunately, 8-bit bytes are hard to check for; but the
+@comment exit status is enough to sniff the crash in broken versions.
+
+@comment xerr: ignore
+@example
+format(`%'format(`%c', `128'))
+@result{}
+@end example
+@end ignore
+
 @node Arithmetic
 @chapter Macros for doing arithmetic