Use allocator from code for pcre2_match_data_create_from_pattern if NULL

passed.

doc/html/pcre2_match_data_create_from_pattern.html

@@ -35,8 +35,9 @@ the matched string and any captured substrings.
 </P>
 <P>
 The second argument points to a general context, for custom memory management,
-or is NULL for system memory management. The result of the function is NULL if
-the memory for the block could not be obtained.
+or is NULL to use the same memory allocator as was used for the compiled
+pattern. The result of the function is NULL if the memory for the block could
+not be obtained.
 </P>
 <P>
 There is a complete description of the PCRE2 native API in the

doc/html/pcre2api.html

@@ -1709,14 +1709,18 @@ substrings. A minimum of at least 1 pair is imposed by
 matched string.
 </P>
 <P>
-For <b>pcre2_match_data_create_from_pattern()</b>, the first argument is a
-pointer to a compiled pattern. In this case the ovector is created to be
-exactly the right size to hold all the substrings a pattern might capture.
+The second argument of <b>pcre2_match_data_create()</b> is a pointer to a
+general context, which can specify custom memory management for obtaining the
+memory for the match data block. If you are not using custom memory management,
+pass NULL, which causes <b>malloc()</b> to be used.
 </P>
 <P>
-The second argument of both these functions is a pointer to a general context,
-which can specify custom memory management for obtaining the memory for the
-match data block. If you are not using custom memory management, pass NULL.
+For <b>pcre2_match_data_create_from_pattern()</b>, the first argument is a
+pointer to a compiled pattern. The ovector is created to be exactly the right
+size to hold all the substrings a pattern might capture. The second argument is
+again a pointer to a general context, but in this case if NULL is passed, the
+memory is obtained using the same allocator that was used for the compiled
+pattern (custom or default).
 </P>
 <P>
 A match data block can be used many times, with the same or different compiled

doc/pcre2.txt

@@ -1728,15 +1728,17 @@ THE MATCH DATA BLOCK
        pcre2_match_data_create(), so it is always possible to return the over-
        all matched string.
 
-       For  pcre2_match_data_create_from_pattern(),  the  first  argument is a
-       pointer to a compiled pattern. In this case the ovector is  created  to
-       be  exactly  the  right size to hold all the substrings a pattern might
-       capture.
+       The second argument of pcre2_match_data_create() is a pointer to a gen-
+       eral context, which can specify custom memory management for  obtaining
+       the memory for the match data block. If you are not using custom memory
+       management, pass NULL, which causes malloc() to be used.
 
-       The second argument of both these functions is a pointer to  a  general
-       context,  which  can specify custom memory management for obtaining the
-       memory for the match data block. If you are  not  using  custom  memory
-       management, pass NULL.
+       For pcre2_match_data_create_from_pattern(), the  first  argument  is  a
+       pointer to a compiled pattern. The ovector is created to be exactly the
+       right size to hold all the substrings a pattern might capture. The sec-
+       ond  argument is again a pointer to a general context, but in this case
+       if NULL is passed, the memory is obtained using the same allocator that
+       was used for the compiled pattern (custom or default).
 
        A  match  data block can be used many times, with the same or different
        compiled patterns. When it is no longer needed, it should be  freed  by

doc/pcre2_match_data_create_from_pattern.3

@@ -22,8 +22,9 @@ pairs of offsets that are required in the match data block. These form the
 the matched string and any captured substrings.
 .P
 The second argument points to a general context, for custom memory management,
-or is NULL for system memory management. The result of the function is NULL if
-the memory for the block could not be obtained.
+or is NULL to use the same memory allocator as was used for the compiled
+pattern. The result of the function is NULL if the memory for the block could
+not be obtained.
 .P
 There is a complete description of the PCRE2 native API in the
 .\" HREF

doc/pcre2api.3

@@ -1700,13 +1700,17 @@ substrings. A minimum of at least 1 pair is imposed by
 \fBpcre2_match_data_create()\fP, so it is always possible to return the overall
 matched string.
 .P
-For \fBpcre2_match_data_create_from_pattern()\fP, the first argument is a
-pointer to a compiled pattern. In this case the ovector is created to be
-exactly the right size to hold all the substrings a pattern might capture.
+The second argument of \fBpcre2_match_data_create()\fP is a pointer to a
+general context, which can specify custom memory management for obtaining the
+memory for the match data block. If you are not using custom memory management,
+pass NULL, which causes \fBmalloc()\fP to be used.
 .P
-The second argument of both these functions is a pointer to a general context,
-which can specify custom memory management for obtaining the memory for the
-match data block. If you are not using custom memory management, pass NULL.
+For \fBpcre2_match_data_create_from_pattern()\fP, the first argument is a
+pointer to a compiled pattern. The ovector is created to be exactly the right
+size to hold all the substrings a pattern might capture. The second argument is
+again a pointer to a general context, but in this case if NULL is passed, the
+memory is obtained using the same allocator that was used for the compiled
+pattern (custom or default).
 .P
 A match data block can be used many times, with the same or different compiled
 patterns. When it is no longer needed, it should be freed by calling

src/pcre2_match_data.c

@@ -72,10 +72,13 @@ return yield;
 *  Create a match data block using pattern data  *
 *************************************************/
 
+/* If no context is supplied, use the memory allocator from the code. */
+
 PCRE2_EXP_DEFN pcre2_match_data * PCRE2_CALL_CONVENTION
 pcre2_match_data_create_from_pattern(const pcre2_code *code,
   pcre2_general_context *gcontext)
 {
+if (gcontext == NULL) gcontext = (pcre2_general_context *)code;
 return pcre2_match_data_create(((pcre2_real_code *)code)->top_bracket + 1,
   gcontext);
 }