Provide pcre2_match_data_create_with_frames() to avoid start stack frames.

src/pcre2.h.generic

@@ -672,6 +672,8 @@ PCRE2_EXP_DECL int PCRE2_CALL_CONVENTION \
 #define PCRE2_MATCH_FUNCTIONS \
 PCRE2_EXP_DECL pcre2_match_data PCRE2_CALL_CONVENTION \
   *pcre2_match_data_create(uint32_t, pcre2_general_context *); \
+PCRE2_EXP_DECL pcre2_match_data PCRE2_CALL_CONVENTION \
+  *pcre2_match_data_create_with_frames(uint32_t, pcre2_general_context *); \
 PCRE2_EXP_DECL pcre2_match_data PCRE2_CALL_CONVENTION \
   *pcre2_match_data_create_from_pattern(const pcre2_code *, \
     pcre2_general_context *); \
@@ -868,6 +870,7 @@ pcre2_compile are called by application code. */
 #define pcre2_match_context_create            PCRE2_SUFFIX(pcre2_match_context_create_)
 #define pcre2_match_context_free              PCRE2_SUFFIX(pcre2_match_context_free_)
 #define pcre2_match_data_create               PCRE2_SUFFIX(pcre2_match_data_create_)
+#define pcre2_match_data_create_with_frames   PCRE2_SUFFIX(pcre2_match_data_create_with_frames_)
 #define pcre2_match_data_create_from_pattern  PCRE2_SUFFIX(pcre2_match_data_create_from_pattern_)
 #define pcre2_match_data_free                 PCRE2_SUFFIX(pcre2_match_data_free_)
 #define pcre2_pattern_convert                 PCRE2_SUFFIX(pcre2_pattern_convert_)

src/pcre2.h.in

@@ -672,6 +672,8 @@ PCRE2_EXP_DECL int PCRE2_CALL_CONVENTION \
 #define PCRE2_MATCH_FUNCTIONS \
 PCRE2_EXP_DECL pcre2_match_data PCRE2_CALL_CONVENTION \
   *pcre2_match_data_create(uint32_t, pcre2_general_context *); \
+PCRE2_EXP_DECL pcre2_match_data PCRE2_CALL_CONVENTION \
+  *pcre2_match_data_create_with_frames(uint32_t, pcre2_general_context *); \
 PCRE2_EXP_DECL pcre2_match_data PCRE2_CALL_CONVENTION \
   *pcre2_match_data_create_from_pattern(const pcre2_code *, \
     pcre2_general_context *); \
@@ -868,6 +870,7 @@ pcre2_compile are called by application code. */
 #define pcre2_match_context_create            PCRE2_SUFFIX(pcre2_match_context_create_)
 #define pcre2_match_context_free              PCRE2_SUFFIX(pcre2_match_context_free_)
 #define pcre2_match_data_create               PCRE2_SUFFIX(pcre2_match_data_create_)
+#define pcre2_match_data_create_with_frames   PCRE2_SUFFIX(pcre2_match_data_create_with_frames_)
 #define pcre2_match_data_create_from_pattern  PCRE2_SUFFIX(pcre2_match_data_create_from_pattern_)
 #define pcre2_match_data_free                 PCRE2_SUFFIX(pcre2_match_data_free_)
 #define pcre2_pattern_convert                 PCRE2_SUFFIX(pcre2_pattern_convert_)

src/pcre2_intmodedep.h

@@ -615,6 +615,8 @@ here.) */
 #undef  LOOKBEHIND_MAX
 #define LOOKBEHIND_MAX UINT16_MAX
 
+struct heapframe; /* see below */
+
 typedef struct pcre2_real_code {
   pcre2_memctl memctl;            /* Memory control fields */
   const uint8_t *tables;          /* The character tables */
@@ -661,6 +663,7 @@ typedef struct pcre2_real_match_data {
   uint8_t          flags;         /* Various flags */
   uint16_t         oveccount;     /* Number of pairs */
   int              rc;            /* The return code from the match */
+  struct heapframe *start_frames; /* Initial heap frames (NULL for stack) */
   PCRE2_SIZE       ovector[131072]; /* Must be last in the structure */
 } pcre2_real_match_data;
 

src/pcre2_match.c

@@ -6268,35 +6268,10 @@ switch (Freturn_id)
 #undef LBL
 }
 
-
-/*************************************************
-*           Match a Regular Expression           *
-*************************************************/
-
-/* This function applies a compiled pattern to a subject string and picks out
-portions of the string if it matches. Two elements in the vector are set for
-each substring: the offsets to the start and end of the substring.
-
-Arguments:
-  code            points to the compiled expression
-  subject         points to the subject string
-  length          length of subject string (may contain binary zeros)
-  start_offset    where to start in the subject string
-  options         option bits
-  match_data      points to a match_data block
-  mcontext        points a PCRE2 context
-
-Returns:          > 0 => success; value is the number of ovector pairs filled
-                  = 0 => success, but ovector is not big enough
-                  = -1 => failed to match (PCRE2_ERROR_NOMATCH)
-                  = -2 => partial match (PCRE2_ERROR_PARTIAL)
-                  < -2 => some kind of unexpected problem
-*/
-
-PCRE2_EXP_DEFN int PCRE2_CALL_CONVENTION
-pcre2_match(const pcre2_code *code, PCRE2_SPTR subject, PCRE2_SIZE length,
+static int
+match_start(const pcre2_code *code, PCRE2_SPTR subject, PCRE2_SIZE length,
   PCRE2_SIZE start_offset, uint32_t options, pcre2_match_data *match_data,
-  pcre2_match_context *mcontext)
+  pcre2_match_context *mcontext, heapframe *start_frames)
 {
 int rc;
 int was_zero_terminated = 0;
@@ -6354,24 +6329,7 @@ pcre2_callout_block cb;
 match_block actual_match_block;
 match_block *mb = &actual_match_block;
 
-/* Allocate an initial vector of backtracking frames on the stack. If this
-proves to be too small, it is replaced by a larger one on the heap. To get a
-vector of the size required that is aligned for pointers, allocate it as a
-vector of pointers. */
-
-PCRE2_SPTR stack_frames_vector[START_FRAMES_SIZE/sizeof(PCRE2_SPTR)]
-    PCRE2_KEEP_UNINITIALIZED;
-mb->stack_frames = (heapframe *)stack_frames_vector;
-
-/* Recognize NULL, length 0 as an empty string. */
-
-if (subject == NULL && length == 0) subject = (PCRE2_SPTR)"";
-
-/* Plausibility checks */
-
-if ((options & ~PUBLIC_MATCH_OPTIONS) != 0) return PCRE2_ERROR_BADOPTION;
-if (code == NULL || subject == NULL || match_data == NULL)
-  return PCRE2_ERROR_NULL;
+mb->stack_frames = start_frames;
 
 start_match = subject + start_offset;
 req_cu_ptr = start_match - 1;
@@ -7533,6 +7491,95 @@ else match_data->rc = PCRE2_ERROR_NOMATCH;
 return match_data->rc;
 }
 
+#if defined(__GNUC__) /* Works for clang/ICC too */
+#define MATCH_START_ON_STACK_NOT_INLINABLE 1
+#define MATCH_START_ON_STACK_NOINLINE __attribute__ ((noinline))
+#elif defined(_MSC_VER)
+#define MATCH_START_ON_STACK_NOT_INLINABLE 1
+#define MATCH_START_ON_STACK_NOINLINE __declspec(noinline)
+#else
+#define MATCH_START_ON_STACK_NOT_INLINABLE 0
+#define MATCH_START_ON_STACK_NOINLINE
+#endif
+
+static MATCH_START_ON_STACK_NOINLINE int
+match_start_on_stack(const pcre2_code *code, PCRE2_SPTR subject,
+ PCRE2_SIZE length, PCRE2_SIZE start_offset, uint32_t options,
+ pcre2_match_data *match_data, pcre2_match_context *mcontext)
+{
+/* Allocate an initial vector of backtracking frames on the stack. If this
+proves to be too small, it is replaced by a larger one on the heap. To get a
+vector of the size required that is aligned for pointers, allocate it as a
+vector of pointers. */
+
+PCRE2_SPTR stack_frames_vector[START_FRAMES_SIZE/sizeof(PCRE2_SPTR)]
+    PCRE2_KEEP_UNINITIALIZED;
+
+return match_start(code, subject, length, start_offset, options, match_data,
+                   mcontext, (heapframe *)stack_frames_vector);
+}
+
+/*************************************************
+*           Match a Regular Expression           *
+*************************************************/
+
+/* This function applies a compiled pattern to a subject string and picks out
+portions of the string if it matches. Two elements in the vector are set for
+each substring: the offsets to the start and end of the substring.
+
+Arguments:
+  code            points to the compiled expression
+  subject         points to the subject string
+  length          length of subject string (may contain binary zeros)
+  start_offset    where to start in the subject string
+  options         option bits
+  match_data      points to a match_data block
+  mcontext        points a PCRE2 context
+
+Returns:          > 0 => success; value is the number of ovector pairs filled
+                  = 0 => success, but ovector is not big enough
+                  = -1 => failed to match (PCRE2_ERROR_NOMATCH)
+                  = -2 => partial match (PCRE2_ERROR_PARTIAL)
+                  < -2 => some kind of unexpected problem
+*/
+
+PCRE2_EXP_DEFN int PCRE2_CALL_CONVENTION
+pcre2_match(const pcre2_code *code, PCRE2_SPTR subject, PCRE2_SIZE length,
+  PCRE2_SIZE start_offset, uint32_t options, pcre2_match_data *match_data,
+  pcre2_match_context *mcontext)
+{
+/* Recognize NULL, length 0 as an empty string. */
+
+if (subject == NULL && length == 0) subject = (PCRE2_SPTR)"";
+
+/* Plausibility checks */
+
+if ((options & ~PUBLIC_MATCH_OPTIONS) != 0) return PCRE2_ERROR_BADOPTION;
+if (code == NULL || subject == NULL || match_data == NULL)
+  return PCRE2_ERROR_NULL;
+
+/* Use stack frames only if match_data does not provide ones, playing some
+ * noinline/indirection games to avoid allocating the frames on stack here
+ * when pcre2_match_data_create_with_frames() was used. */
+if (match_data->start_frames == NULL) {
+#if MATCH_START_ON_STACK_NOT_INLINABLE /* garanteed by the compiler */
+  return match_start_on_stack(code, subject, length, start_offset,
+                              options, match_data, mcontext);
+#else /* indirection that prevents inlining */
+  int (*volatile fn)(const pcre2_code*, PCRE2_SPTR, PCRE2_SIZE,
+                     PCRE2_SIZE, uint32_t, pcre2_match_data*,
+                     pcre2_match_context*) = &match_start_on_stack;
+  return (*fn)(code, subject, length, start_offset, options, match_data,
+               mcontext);
+#endif
+}
+
+/* Use initial heap frames from match_data. */
+return match_start(code, subject, length, start_offset,
+                   options, match_data, mcontext,
+                   match_data->start_frames);
+}
+
 /* These #undefs are here to enable unity builds with CMake. */
 
 #undef NLBLOCK /* Block containing newline information */

src/pcre2_match_data.c

@@ -45,6 +45,36 @@ POSSIBILITY OF SUCH DAMAGE.
 
 #include "pcre2_internal.h"
 
+static inline PCRE2_SIZE
+start_frames_offset(uint32_t oveccount)
+{
+  return ((2*oveccount*sizeof(PCRE2_SIZE) + HEAPFRAME_ALIGNMENT - 1) &
+          ~(HEAPFRAME_ALIGNMENT - 1));
+}
+
+static inline pcre2_match_data *
+match_data_create(uint32_t oveccount, int with_frames,
+  pcre2_general_context *gcontext)
+{
+pcre2_match_data *yield;
+PCRE2_SIZE ovecsize;
+if (oveccount < 1) oveccount = 1;
+if (with_frames)
+  ovecsize = start_frames_offset(oveccount) + START_FRAMES_SIZE;
+else
+  ovecsize = 2*oveccount*sizeof(PCRE2_SIZE);
+yield = PRIV(memctl_malloc)(
+  offsetof(pcre2_match_data, ovector) + ovecsize, (pcre2_memctl *)gcontext);
+if (yield == NULL) return NULL;
+yield->oveccount = oveccount;
+if (with_frames)
+  yield->start_frames = (heapframe *)
+    ((char *)yield->ovector + ovecsize - START_FRAMES_SIZE);
+else
+  yield->start_frames = NULL; /* use stack frames from pcre2_match() */
+yield->flags = 0;
+return yield;
+}
 
 
 /*************************************************
@@ -56,15 +86,22 @@ POSSIBILITY OF SUCH DAMAGE.
 PCRE2_EXP_DEFN pcre2_match_data * PCRE2_CALL_CONVENTION
 pcre2_match_data_create(uint32_t oveccount, pcre2_general_context *gcontext)
 {
-pcre2_match_data *yield;
-if (oveccount < 1) oveccount = 1;
-yield = PRIV(memctl_malloc)(
-  offsetof(pcre2_match_data, ovector) + 2*oveccount*sizeof(PCRE2_SIZE),
-  (pcre2_memctl *)gcontext);
-if (yield == NULL) return NULL;
-yield->oveccount = oveccount;
-yield->flags = 0;
-return yield;
+  return match_data_create(oveccount, 0, gcontext);
+}
+
+
+
+/*************************************************
+*  Create a match data block given ovector size  *
+*************************************************/
+
+/* A minimum of 1 is imposed on the number of ovector pairs. */
+
+PCRE2_EXP_DEFN pcre2_match_data * PCRE2_CALL_CONVENTION
+pcre2_match_data_create_with_frames(uint32_t oveccount,
+  pcre2_general_context *gcontext)
+{
+  return match_data_create(oveccount, 1, gcontext);
 }
 
 
@@ -79,9 +116,9 @@ PCRE2_EXP_DEFN pcre2_match_data * PCRE2_CALL_CONVENTION
 pcre2_match_data_create_from_pattern(const pcre2_code *code,
   pcre2_general_context *gcontext)
 {
+uint32_t oveccount = ((pcre2_real_code *)code)->top_bracket + 1;
 if (gcontext == NULL) gcontext = (pcre2_general_context *)code;
-return pcre2_match_data_create(((pcre2_real_code *)code)->top_bracket + 1,
-  gcontext);
+return match_data_create(oveccount, 0, gcontext);
 }
 
 
@@ -160,7 +197,9 @@ PCRE2_EXP_DEFN PCRE2_SIZE PCRE2_CALL_CONVENTION
 pcre2_get_match_data_size(pcre2_match_data *match_data)
 {
 return offsetof(pcre2_match_data, ovector) +
-  2 * (match_data->oveccount) * sizeof(PCRE2_SIZE);
+  (match_data->start_frames
+   ? start_frames_offset(match_data->oveccount) + START_FRAMES_SIZE
+   : 2 * match_data->oveccount * sizeof(PCRE2_SIZE));
 }
 
 /* End of pcre2_match_data.c */

src/pcre2test.c

@@ -1248,6 +1248,14 @@ are supported. */
   else \
     G(a,32) = pcre2_match_data_create_32(b,c)
 
+#define PCRE2_MATCH_DATA_CREATE_WITH_FRAMES(a,b,c) \
+  if (test_mode == PCRE8_MODE) \
+    G(a,8) = pcre2_match_data_create_with_frames_8(b,c); \
+  else if (test_mode == PCRE16_MODE) \
+    G(a,16) = pcre2_match_data_create_with_frames_16(b,c); \
+  else \
+    G(a,32) = pcre2_match_data_create_with_frames_32(b,c)
+
 #define PCRE2_MATCH_DATA_CREATE_FROM_PATTERN(a,b,c) \
   if (test_mode == PCRE8_MODE) \
     G(a,8) = pcre2_match_data_create_from_pattern_8(G(b,8),c); \
@@ -1766,6 +1774,12 @@ the three different cases. */
   else \
     G(a,BITTWO) = G(pcre2_match_data_create_,BITTWO)(b,c)
 
+#define PCRE2_MATCH_DATA_CREATE_WITH_FRAMES(a,b,c) \
+  if (test_mode == G(G(PCRE,BITONE),_MODE)) \
+    G(a,BITONE) = G(pcre2_match_data_create_with_frames_,BITONE)(b,c); \
+  else \
+    G(a,BITTWO) = G(pcre2_match_data_create_with_frames_,BITTWO)(b,c)
+
 #define PCRE2_MATCH_DATA_CREATE_FROM_PATTERN(a,b,c) \
   if (test_mode == G(G(PCRE,BITONE),_MODE)) \
     G(a,BITONE) = G(pcre2_match_data_create_from_pattern_,BITONE)(G(b,BITONE),c); \
@@ -2071,6 +2085,8 @@ the three different cases. */
 #define PCRE2_MATCH(a,b,c,d,e,f,g,h) \
   a = pcre2_match_8(G(b,8),(PCRE2_SPTR8)c,d,e,f,G(g,8),h)
 #define PCRE2_MATCH_DATA_CREATE(a,b,c) G(a,8) = pcre2_match_data_create_8(b,c)
+#define PCRE2_MATCH_DATA_CREATE_WITH_FRAMES(a,b,c) \
+  G(a,8) = pcre2_match_data_create_with_frames_8(b,c)
 #define PCRE2_MATCH_DATA_CREATE_FROM_PATTERN(a,b,c) \
   G(a,8) = pcre2_match_data_create_from_pattern_8(G(b,8),c)
 #define PCRE2_MATCH_DATA_FREE(a) pcre2_match_data_free_8(G(a,8))
@@ -2178,6 +2194,8 @@ the three different cases. */
 #define PCRE2_MATCH(a,b,c,d,e,f,g,h) \
   a = pcre2_match_16(G(b,16),(PCRE2_SPTR16)c,d,e,f,G(g,16),h)
 #define PCRE2_MATCH_DATA_CREATE(a,b,c) G(a,16) = pcre2_match_data_create_16(b,c)
+#define PCRE2_MATCH_DATA_CREATE_WITH_FRAMES(a,b,c) \
+  G(a,16) = pcre2_match_data_create_with_frames_16(b,c)
 #define PCRE2_MATCH_DATA_CREATE_FROM_PATTERN(a,b,c) \
   G(a,16) = pcre2_match_data_create_from_pattern_16(G(b,16),c)
 #define PCRE2_MATCH_DATA_FREE(a) pcre2_match_data_free_16(G(a,16))
@@ -2285,6 +2303,8 @@ the three different cases. */
 #define PCRE2_MATCH(a,b,c,d,e,f,g,h) \
   a = pcre2_match_32(G(b,32),(PCRE2_SPTR32)c,d,e,f,G(g,32),h)
 #define PCRE2_MATCH_DATA_CREATE(a,b,c) G(a,32) = pcre2_match_data_create_32(b,c)
+#define PCRE2_MATCH_DATA_CREATE_WITH_FRAMES(a,b,c) \
+  G(a,32) = pcre2_match_data_create_with_frames_32(b,c)
 #define PCRE2_MATCH_DATA_CREATE_FROM_PATTERN(a,b,c) \
   G(a,32) = pcre2_match_data_create_from_pattern_32(G(b,32),c)
 #define PCRE2_MATCH_DATA_FREE(a) pcre2_match_data_free_32(G(a,32))
@@ -7287,7 +7307,7 @@ else
   {
   max_oveccount = dat_datctl.oveccount;
   PCRE2_MATCH_DATA_FREE(match_data);
-  PCRE2_MATCH_DATA_CREATE(match_data, max_oveccount, NULL);
+  PCRE2_MATCH_DATA_CREATE_WITH_FRAMES(match_data, max_oveccount, NULL);
   }
 
 if (CASTVAR(void *, match_data) == NULL)
@@ -9170,7 +9190,7 @@ max_oveccount = DEFAULT_OVECCOUNT;
   G(dat_context,BITS) = G(pcre2_match_context_copy_,BITS)(G(default_dat_context,BITS)); \
   G(default_con_context,BITS) = G(pcre2_convert_context_create_,BITS)(G(general_context,BITS)); \
   G(con_context,BITS) = G(pcre2_convert_context_copy_,BITS)(G(default_con_context,BITS)); \
-  G(match_data,BITS) = G(pcre2_match_data_create_,BITS)(max_oveccount, G(general_context,BITS))
+  G(match_data,BITS) = G(pcre2_match_data_create_with_frames_,BITS)(max_oveccount, G(general_context,BITS))
 
 #define CONTEXTTESTS \
   (void)G(pcre2_set_compile_extra_options_,BITS)(G(pat_context,BITS), 0); \