From 340f224bd085965d5ff724afdafa04759f8a040f Mon Sep 17 00:00:00 2001
From: Ben Pfaff <blp@cs.stanford.edu>
Date: Wed, 1 Sep 2021 10:02:26 -0700
Subject: [PATCH] macro: Fix crash for !QUOTE of a quoted string.

This revealed that the tests didn't include anything for !QUOTE and
!UNQUOTE, even though the manual had lots of examples.  I added a test for
these and for !NULL, which had also been forgotten.

Thanks to Frans Houweling for reporting the bug.
---
 doc/flow-control.texi            |  4 ++
 src/language/lexer/macro.c       |  3 +-
 tests/language/control/define.at | 66 ++++++++++++++++++++++++++++++++
 3 files changed, 72 insertions(+), 1 deletion(-)

diff --git a/doc/flow-control.texi b/doc/flow-control.texi
index d3235612b9..23539bcfb6 100644
--- a/doc/flow-control.texi
+++ b/doc/flow-control.texi
@@ -578,6 +578,8 @@ Expands to a number token representing the number of characters in
 @deffn {Macro Function} !NULL
 Expands to an empty character sequence.
 
+@c Keep these examples in sync with the test for !NULL in
+@c tests/language/control/define.at:
 @example
 !NULL                        @expansion{} @r{empty}
 !QUOTE(!NULL)                @expansion{} ''
@@ -596,6 +598,8 @@ to the string's contents, with the quotes removed and any doubled
 quote marks reduced to singletons.  If the argument was not a quoted
 string, @code{!UNQUOTE} expands to the argument unchanged.
 
+@c Keep these examples in sync with the test for !QUOTE and !UNQUOTE in
+@c tests/language/control/define.at:
 @example
 !QUOTE(123.0)                @expansion{} '123.0'
 !QUOTE( 123 )                @expansion{} '123'
diff --git a/src/language/lexer/macro.c b/src/language/lexer/macro.c
index 742b8771ac..814740bfac 100644
--- a/src/language/lexer/macro.c
+++ b/src/language/lexer/macro.c
@@ -1038,7 +1038,8 @@ unquote_string (const char *s, enum segmenter_mode segmenter_mode,
       return false;
     }
 
-  ds_put_substring (content, token1.string);
+  if (content)
+    ds_put_substring (content, token1.string);
   token_uninit (&token1);
   return true;
 }
diff --git a/tests/language/control/define.at b/tests/language/control/define.at
index 9a7594b81b..204ed2efd3 100644
--- a/tests/language/control/define.at
+++ b/tests/language/control/define.at
@@ -880,6 +880,72 @@ AT_CHECK([pspp --testing-mode define.sps], [0], [dnl
 ])
 AT_CLEANUP
 
+dnl Keep this test in sync with the examples for !NULL in the manual.
+AT_SETUP([macro expansion - !NULL])
+AT_KEYWORDS([NULL])
+AT_DATA([define.sps], [dnl
+DEFINE !n()
+!NULL.
+!QUOTE(!NULL).
+!ENDDEFINE.
+DEBUG EXPAND.
+!n.
+])
+AT_CAPTURE_FILE([define.sps])
+AT_CHECK([pspp --testing-mode define.sps], [0], [dnl
+.
+''.
+])
+AT_CLEANUP
+
+dnl Keep this test in sync with the examples for !QUOTE and !UNQUOTE in the manual.
+AT_SETUP([macro expansion - !QUOTE and !UNQUOTE])
+AT_KEYWORDS([QUOTE UNQUOTE])
+AT_DATA([define.sps], [dnl
+DEFINE !q(!POS !CMDEND)
+!QUOTE(123.0).
+!QUOTE( 123 ).
+!QUOTE('a b c').
+!QUOTE("a b c").
+!QUOTE(!1).
+
+!UNQUOTE(123.0).
+!UNQUOTE( 123 ).
+!UNQUOTE('a b c').
+!UNQUOTE("a b c").
+!UNQUOTE(!1).
+
+!QUOTE(!UNQUOTE(123.0)).
+!QUOTE(!UNQUOTE( 123 )).
+!QUOTE(!UNQUOTE('a b c')).
+!QUOTE(!UNQUOTE("a b c")).
+!QUOTE(!UNQUOTE(!1)).
+!ENDDEFINE.
+DEBUG EXPAND.
+!q a 'b' c.
+])
+AT_CAPTURE_FILE([define.sps])
+AT_CHECK([pspp --testing-mode define.sps], [0], [dnl
+'123.0'.
+'123'.
+'a b c'.
+"a b c".
+'a ''b'' c'.
+
+123.0.
+123.
+a b c.
+a b c.
+a 'b' c.
+
+'123.0'.
+'123'.
+'a b c'.
+'a b c'.
+'a ''b'' c'.
+])
+AT_CLEANUP
+
 dnl Keep this test in sync with the examples for !SUBSTR in the manual.
 AT_SETUP([macro expansion - !SUBSTR])
 AT_KEYWORDS([SUBSTR])
-- 
2.30.2