A better fix for oss-fuzz 1465.

src/pcre2_intmodedep.h

@@ -793,7 +793,11 @@ typedef struct heapframe {
 #endif
 
   /* The rest have to be copied from the previous frame whenever a new frame
-  becomes current. */
+  becomes current. The final field is specified as a large vector so that 
+  runtime array bound checks don't catch references to it. However, for any 
+  specific call to pcre2_match() the memory allocated for each frame structure 
+  allows for exactly the right size ovector for the number of capturing 
+  parentheses. */
 
   PCRE2_SPTR eptr;           /* MUST BE FIRST */
   PCRE2_SPTR start_match;    /* Can be adjusted by \K */
@@ -802,7 +806,7 @@ typedef struct heapframe {
   uint32_t capture_last;     /* Most recent capture */
   PCRE2_SIZE last_group_offset;  /* Saved offset to most recent group frame */
   PCRE2_SIZE offset_top;     /* Offset after highest capture */
-  PCRE2_SIZE ovector[2];     /* Must be last in the structure */
+  PCRE2_SIZE ovector[10000]; /* Must be last in the structure */
 } heapframe;
 
 typedef char check_heapframe_size[

src/pcre2_match.c

@@ -189,7 +189,7 @@ end of the backtrack frame, but when there are capturing parentheses the space
 allocated is bigger so we want to be able to address more elements. Without the 
 case, -fsanitize=undefined grumbles at this. */
 
-#define Fovector           ((PCRE2_SIZE *)(F->ovector))
+#define Fovector           F->ovector
 
 
 #ifdef DEBUG_FRAMES_DISPLAY
@@ -6281,7 +6281,8 @@ The last of these is changed within the match() function if the frame vector
 has to be expanded. We therefore put it into the match block so that it is
 correct when calling match() more than once for non-anchored patterns. */
 
-frame_size = sizeof(heapframe) + ((re->top_bracket - 1) * 2 * sizeof(PCRE2_SIZE));
+frame_size = offsetof(heapframe, ovector) + 
+  re->top_bracket * 2 * sizeof(PCRE2_SIZE);
 
 /* Limits set in the pattern override the match context only if they are
 smaller. */

src/pcre2_pattern_info.c

@@ -160,8 +160,8 @@ switch(what)
   break;
 
   case PCRE2_INFO_FRAMESIZE:
-  *((size_t *)where) = sizeof(heapframe) +
-    ((re->top_bracket - 1) * 2 * sizeof(PCRE2_SIZE));
+  *((size_t *)where) = offsetof(heapframe, ovector) +
+    re->top_bracket * 2 * sizeof(PCRE2_SIZE);
   break;
 
   case PCRE2_INFO_HASBACKSLASHC: