Test hex('x...').

[p5sagit/p5-mst-13.2.git] / t / op / repeat.t

diff --git a/t/op/repeat.t b/t/op/repeat.t
old mode 100644 (file)
new mode 100755 (executable)
index a494b99..c030ba9
--- a/t/op/repeat.t
+++ b/t/op/repeat.t
@@ -1,8 +1,8 @@
 #!./perl
 
-# $Header: repeat.t,v 4.0 91/03/20 01:54:26 lwall Locked $
+# $RCSfile: repeat.t,v $$Revision: 4.1 $$Date: 92/08/07 18:28:21 $
 
-print "1..19\n";
+print "1..20\n";
 
 # compile time
 
@@ -40,3 +40,59 @@ print join(':', () x 4) eq '' ? "ok 16\n" : "not ok 16\n";
 print join(':', (9) x 4) eq '9:9:9:9' ? "ok 17\n" : "not ok 17\n";
 print join(':', (9,9) x 4) eq '9:9:9:9:9:9:9:9' ? "ok 18\n" : "not ok 18\n";
 print join('', (split(//,"123")) x 2) eq '123123' ? "ok 19\n" : "not ok 19\n";
+
+#
+# The test #20 is actually testing for Digital C compiler optimizer bug,
+# present in Dec C versions 5.* and 6.0 (used in Digital UNIX and VMS),
+# found in December 1998.  The bug was reported to Digital^WCompaq as
+#     DECC 2745 (21-Dec-1998)
+# GEM_BUGS 7619 (23-Dec-1998)
+# As of April 1999 the bug has been fixed in Tru64 UNIX 5.0 and is planned
+# to be fixed also in 4.0G.
+#
+# The bug was as follows: broken code was produced for util.c:repeatcpy()
+# (a utility function for the 'x' operator) in the case *all* these
+# four conditions held:
+#
+# (1) len == 1
+# (2) "from" had the 8th bit on in its single character
+# (3) count > 7 (the 'x' count > 16)
+# (4) the highest optimization level was used in compilation
+#     (which is the default when compiling Perl)
+#
+# The bug looked like this (. being the eight-bit character and ? being \xff):
+#
+# 16 ................
+# 17 .........???????.
+# 18 .........???????..
+# 19 .........???????...
+# 20 .........???????....
+# 21 .........???????.....
+# 22 .........???????......
+# 23 .........???????.......
+# 24 .........???????.???????
+# 25 .........???????.???????.
+#
+# The bug was triggered in the "if (len == 1)" branch.  The fix
+# was to introduce a new temporary variable.  In diff -u format:
+#
+#     register char *frombase = from;
+# 
+#     if (len == 1) {
+#-       todo = *from;
+#+       register char c = *from;
+#        while (count-- > 0)
+#-           *to++ = todo;
+#+           *to++ = c;
+#        return;
+#     }
+#
+# The bug could also be (obscurely) avoided by changing "from" to
+# be an unsigned char pointer.
+#
+# This obscure bug was not found by the then test suite but instead
+# by Mark.Martinec@nsc.ijs.si while trying to install Digest-MD5-2.00.
+#
+# jhi@iki.fi
+#
+print "\xdd" x 24 eq "\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd\xdd" ? "ok 20\n" : "not ok 20\n";