grep: fix -zxP bug

* NEWS: Document this.
* src/pcresearch.c (Pcompile): Search a line at a time if -x is
used, since -x uses ^ and $.
* tests/pcre: Test this.

3 files changed, 24 insertions, 17 deletions

diff --git a/NEWS b/NEWS
index 978ec555..4972c018 100644
--- a/NEWS
+++ b/NEWS
@@ -10,9 +10,9 @@ GNU grep NEWS                                    -*- outline -*-
   >/dev/null" where PROGRAM dies when writing into a broken pipe.
   [bug introduced in grep-2.26]
 
-  grep -Pz no longer rejects patterns containing ^ and $, and is
-  more cautious about special patterns like (?-m) and (*FAIL).
-  [bug introduced in grep-2.23]
+  grep -Pz no longer rejects patterns containing ^ and $, is more
+  cautious about special patterns like (?-m) and (*FAIL), and works
+  when combined with -x.  [bug introduced in grep-2.23]
 
   grep -m0 -L PAT FILE now outputs "FILE".  [bug introduced in grep-2.5]
 
diff --git a/src/pcresearch.c b/src/pcresearch.c
index 439945aa..01616c2c 100644
--- a/src/pcresearch.c
+++ b/src/pcresearch.c
@@ -128,22 +128,28 @@ Pcompile (char const *pattern, size_t size)
 
   if (! eolbyte)
     {
-      bool escaped = false;
-      bool after_unescaped_left_bracket = false;
-      for (p = pattern; *p; p++)
-        if (escaped)
-          escaped = after_unescaped_left_bracket = false;
-        else
-          {
-            if (*p == '$' || (*p == '^' && !after_unescaped_left_bracket)
-                || (*p == '(' && (p[1] == '?' || p[1] == '*')))
+      bool line_at_a_time = match_lines;
+      if (! line_at_a_time)
+        {
+          bool escaped = false;
+          bool after_unescaped_left_bracket = false;
+          for (p = pattern; *p; p++)
+            if (escaped)
+              escaped = after_unescaped_left_bracket = false;
+            else
               {
-                flags = (flags & ~ PCRE_MULTILINE) | PCRE_DOLLAR_ENDONLY;
-                break;
+                if (*p == '$' || (*p == '^' && !after_unescaped_left_bracket)
+                    || (*p == '(' && (p[1] == '?' || p[1] == '*')))
+                  {
+                    line_at_a_time = true;
+                    break;
+                  }
+                escaped = *p == '\\';
+                after_unescaped_left_bracket = *p == '[';
               }
-            escaped = *p == '\\';
-            after_unescaped_left_bracket = *p == '[';
-          }
+        }
+      if (line_at_a_time)
+        flags = (flags & ~ PCRE_MULTILINE) | PCRE_DOLLAR_ENDONLY;
     }
 
   *n = '\0';
diff --git a/tests/pcre b/tests/pcre
index 653ef221..a290099a 100755
--- a/tests/pcre
+++ b/tests/pcre
@@ -17,5 +17,6 @@ echo | grep -zP '\s$' || fail=1
 echo '.ab' | returns_ 1 grep -Pwx ab || fail=1
 echo x | grep -Pz '[^a]' || fail=1
 printf 'x\n\0' | returns_ 1 grep -zP 'x$' || fail=1
+printf 'a\nb\0' | grep -zxP a && fail=1
 
 Exit $fail