Drop support for using alloca().

While `alloca()` provides a minor performance boost on Linux and FreeBSD, it provides no advantage on platforms with more modern allocators, such as macOS. In addition, since it is not universally portable, we are forced to maintain both code paths, so we don't even get the advantage of simplicity (from not having to free memory allocated locally).
dag-erling · Sep 11, 2024 · ad55b97 · ad55b97
1 parent 0d33c65
commit ad55b97
Show file tree

Hide file tree

Showing 7 changed files with 0 additions and 135 deletions.
diff --git a/configure.ac b/configure.ac
@@ -104,23 +104,6 @@ AC_USE_SYSTEM_EXTENSIONS
 dnl Make sure locally configured headers are used (this adds the #define to config.h).
 AC_DEFINE(USE_LOCAL_TRE_H, 1, [ Define to ensure locally configured headers are used ])
 
-AC_ARG_WITH(alloca,
-  AS_HELP_STRING(
-    [--without-alloca],
-    [don't use alloca  @<:@default=use@:>@]),
-  [ tre_use_alloca="$withval" ],
-  [ tre_use_alloca="yes" ])
-if test "$tre_use_alloca" = "yes"; then
-  ALLOCA=""
-  AC_FUNC_ALLOCA
-  if test -z "$ALLOCA"; then
-    # alloca() works.
-    AC_DEFINE(TRE_USE_ALLOCA, 1,
-      [ Define if you want TRE to use alloca() instead of malloc() when
-        allocating memory needed for regexec operations. ])
-  fi
-fi
-
 AC_ARG_ENABLE(system-abi,
   AS_HELP_STRING(
     [--enable-system-abi],
@@ -560,7 +543,6 @@ TRE is now configured as follows:
   LD       = $LD
   LDFLAGS  = $LDFLAGS
   LIBS     = $LIBS
-  Use alloca():                       $tre_use_alloca
 
 * TRE options
 

diff --git a/lib/regexec.c b/lib/regexec.c
@@ -10,23 +10,6 @@
 #include <config.h>
 #endif /* HAVE_CONFIG_H */
 
-#ifdef TRE_USE_ALLOCA
-/* AIX requires this to be the first thing in the file.	 */
-#ifndef __GNUC__
-# if HAVE_ALLOCA_H
-#  include <alloca.h>
-# else
-#  ifdef _AIX
- #pragma alloca
-#  else
-#   ifndef alloca /* predefined by HP cc +Olibcalls */
-char *alloca ();
-#   endif
-#  endif
-# endif
-#endif
-#endif /* TRE_USE_ALLOCA */
-
 #include <assert.h>
 #include <stdlib.h>
 #include <string.h>
@@ -142,11 +125,7 @@ tre_match(const tre_tnfa_t *tnfa, const void *string, size_t len,
   int *tags = NULL, eo;
   if (tnfa->num_tags > 0 && nmatch > 0)
     {
-#ifdef TRE_USE_ALLOCA
-      tags = alloca(sizeof(*tags) * tnfa->num_tags);
-#else /* !TRE_USE_ALLOCA */
       tags = malloc(sizeof(*tags) * tnfa->num_tags);
-#endif /* !TRE_USE_ALLOCA */
       if (tags == NULL)
 	return REG_ESPACE;
     }
@@ -162,10 +141,8 @@ tre_match(const tre_tnfa_t *tnfa, const void *string, size_t len,
 	    {
 	      /* The backtracking matcher requires rewind and compare
 		 capabilities from the input stream. */
-#ifndef TRE_USE_ALLOCA
 	      if (tags)
 		free(tags);
-#endif /* !TRE_USE_ALLOCA */
 	      return REG_BADPAT;
 	    }
 	}
@@ -195,10 +172,8 @@ tre_match(const tre_tnfa_t *tnfa, const void *string, size_t len,
   if (status == REG_OK)
     /* A match was found, so fill the submatch registers. */
     tre_fill_pmatch(nmatch, pmatch, tnfa->cflags, tnfa, tags, eo);
-#ifndef TRE_USE_ALLOCA
   if (tags)
     free(tags);
-#endif /* !TRE_USE_ALLOCA */
   return status;
 }
 
@@ -301,22 +276,16 @@ tre_match_approx(const tre_tnfa_t *tnfa, const void *string, size_t len,
 
   if (tnfa->num_tags > 0 && match->nmatch > 0)
     {
-#if TRE_USE_ALLOCA
-      tags = alloca(sizeof(*tags) * tnfa->num_tags);
-#else /* !TRE_USE_ALLOCA */
       tags = malloc(sizeof(*tags) * tnfa->num_tags);
-#endif /* !TRE_USE_ALLOCA */
       if (tags == NULL)
 	return REG_ESPACE;
     }
   status = tre_tnfa_run_approx(tnfa, string, (int)len, type, tags,
 			       match, params, eflags, &eo);
   if (status == REG_OK)
     tre_fill_pmatch(match->nmatch, match->pmatch, tnfa->cflags, tnfa, tags, eo);
-#ifndef TRE_USE_ALLOCA
   if (tags)
     free(tags);
-#endif /* !TRE_USE_ALLOCA */
   return status;
 }
 

diff --git a/lib/tre-match-approx.c b/lib/tre-match-approx.c
@@ -11,21 +11,6 @@
 #endif /* HAVE_CONFIG_H */
 
 /* AIX requires this to be the first thing in the file.	 */
-#ifdef TRE_USE_ALLOCA
-#ifndef __GNUC__
-# if HAVE_ALLOCA_H
-#  include <alloca.h>
-# else
-#  ifdef _AIX
- #pragma alloca
-#  else
-#   ifndef alloca /* predefined by HP cc +Olibcalls */
-char *alloca ();
-#   endif
-#  endif
-# endif
-#endif
-#endif /* TRE_USE_ALLOCA */
 
 #include <assert.h>
 #include <stdlib.h>
@@ -272,11 +257,7 @@ tre_tnfa_run_approx(const tre_tnfa_t *tnfa, const void *string, int len,
     total_bytes += (sizeof(long) - 1) * 3;
 
     /* Allocate the memory. */
-#ifdef TRE_USE_ALLOCA
-    buf = alloca(total_bytes);
-#else /* !TRE_USE_ALLOCA */
     buf = malloc((unsigned)total_bytes);
-#endif /* !TRE_USE_ALLOCA */
     if (!buf)
       return REG_ESPACE;
     memset(buf, 0, (size_t)total_bytes);
@@ -792,10 +773,8 @@ tre_tnfa_run_approx(const tre_tnfa_t *tnfa, const void *string, int len,
   DPRINT(("match end offset = %d, match cost = %d\n", match_eo,
 	  match_costs[TRE_M_COST]));
 
-#ifndef TRE_USE_ALLOCA
   if (buf)
     free(buf);
-#endif /* !TRE_USE_ALLOCA */
 
   match->cost = match_costs[TRE_M_COST];
   match->num_ins = match_costs[TRE_M_NUM_INS];

diff --git a/lib/tre-match-backtrack.c b/lib/tre-match-backtrack.c
@@ -34,23 +34,6 @@
 #include <config.h>
 #endif /* HAVE_CONFIG_H */
 
-#ifdef TRE_USE_ALLOCA
-/* AIX requires this to be the first thing in the file.	 */
-#ifndef __GNUC__
-# if HAVE_ALLOCA_H
-#  include <alloca.h>
-# else
-#  ifdef _AIX
- #pragma alloca
-#  else
-#   ifndef alloca /* predefined by HP cc +Olibcalls */
-char *alloca ();
-#   endif
-#  endif
-# endif
-#endif
-#endif /* TRE_USE_ALLOCA */
-
 #include <assert.h>
 #include <stdlib.h>
 #include <string.h>
@@ -109,17 +92,10 @@ typedef struct tre_backtrack_struct {
 #endif /* !TRE_MBSTATE */
 
 
-#ifdef TRE_USE_ALLOCA
-#define tre_bt_mem_new		  tre_mem_newa
-#define tre_bt_mem_alloc	  tre_mem_alloca
-#define tre_bt_mem_destroy(obj)	  do { } while (0)
-#define xafree(obj)		  do { } while (0) /* do nothing, obj was obtained with alloca() */
-#else /* !TRE_USE_ALLOCA */
 #define tre_bt_mem_new		  tre_mem_new
 #define tre_bt_mem_alloc	  tre_mem_alloc
 #define tre_bt_mem_destroy	  tre_mem_destroy
 #define xafree(obj)		  free(obj)
-#endif /* !TRE_USE_ALLOCA */
 
 
 #define BT_STACK_PUSH(_pos, _str_byte, _str_wide, _state, _state_id, _next_c, _tags, _mbstate) \
@@ -265,11 +241,6 @@ tre_tnfa_run_backtrack(const tre_tnfa_t *tnfa, const void *string,
   DPRINT(("tnfa_execute_backtrack, input type %d\n", type));
   DPRINT(("len = %d\n", len));
 
-#ifdef TRE_USE_ALLOCA
-  tags = alloca(sizeof(*tags) * tnfa->num_tags);
-  pmatch = alloca(sizeof(*pmatch) * tnfa->num_submatches);
-  states_seen = alloca(sizeof(*states_seen) * tnfa->num_states);
-#else /* !TRE_USE_ALLOCA */
   if (tnfa->num_tags)
     {
       tags = malloc(sizeof(*tags) * tnfa->num_tags);
@@ -297,7 +268,6 @@ tre_tnfa_run_backtrack(const tre_tnfa_t *tnfa, const void *string,
 	  goto error_exit;
 	}
     }
-#endif /* !TRE_USE_ALLOCA */
 
  retry:
   {
@@ -653,14 +623,12 @@ tre_tnfa_run_backtrack(const tre_tnfa_t *tnfa, const void *string,
 
  error_exit:
   tre_bt_mem_destroy(mem);
-#ifndef TRE_USE_ALLOCA
   if (tags)
     xafree(tags);
   if (pmatch)
     xafree(pmatch);
   if (states_seen)
     xafree(states_seen);
-#endif /* !TRE_USE_ALLOCA */
 
   return ret;
 }
diff --git a/lib/tre-match-parallel.c b/lib/tre-match-parallel.c
@@ -27,23 +27,6 @@
 #include <config.h>
 #endif /* HAVE_CONFIG_H */
 
-#ifdef TRE_USE_ALLOCA
-/* AIX requires this to be the first thing in the file.	 */
-#ifndef __GNUC__
-# if HAVE_ALLOCA_H
-#  include <alloca.h>
-# else
-#  ifdef _AIX
- #pragma alloca
-#  else
-#   ifndef alloca /* predefined by HP cc +Olibcalls */
-char *alloca ();
-#   endif
-#  endif
-# endif
-#endif
-#endif /* TRE_USE_ALLOCA */
-
 #include <assert.h>
 #include <stdlib.h>
 #include <string.h>
@@ -161,11 +144,7 @@ tre_tnfa_run_parallel(const tre_tnfa_t *tnfa, const void *string, int len,
       + (rbytes + xbytes * tnfa->num_states) * 2 + tbytes + pbytes;
 
     /* Allocate the memory. */
-#ifdef TRE_USE_ALLOCA
-    buf = alloca(total_bytes);
-#else /* !TRE_USE_ALLOCA */
     buf = malloc(total_bytes);
-#endif /* !TRE_USE_ALLOCA */
     if (buf == NULL)
       return REG_ESPACE;
     memset(buf, 0, total_bytes);
@@ -207,10 +186,8 @@ tre_tnfa_run_parallel(const tre_tnfa_t *tnfa, const void *string, int len,
 	str_byte = strchr(orig_str, first);
       if (str_byte == NULL)
 	{
-#ifndef TRE_USE_ALLOCA
 	  if (buf)
 	    free(buf);
-#endif /* !TRE_USE_ALLOCA */
 	  return REG_NOMATCH;
 	}
       DPRINT(("skipped %lu chars\n", (unsigned long)(str_byte - orig_str)));
@@ -485,10 +462,8 @@ tre_tnfa_run_parallel(const tre_tnfa_t *tnfa, const void *string, int len,
 
   DPRINT(("match end offset = %d\n", match_eo));
 
-#ifndef TRE_USE_ALLOCA
   if (buf)
     free(buf);
-#endif /* !TRE_USE_ALLOCA */
 
   *match_end_ofs = match_eo;
   return match_eo >= 0 ? REG_OK : REG_NOMATCH;

diff --git a/win32/tre-config.h b/win32/tre-config.h
@@ -29,10 +29,6 @@
 /* Define to the absolute path to the system regex.h */
 /* #undef TRE_SYSTEM_REGEX_H_PATH */
 
-/* Define if you want TRE to use alloca() instead of malloc() when allocating
-   memory needed for regexec operations. */
-#define TRE_USE_ALLOCA 1
-
 /* Define to include the system regex.h from TRE regex.h */
 /* #undef TRE_USE_SYSTEM_REGEX_H */
 

diff --git a/win32/tre-config.h.in b/win32/tre-config.h.in
@@ -29,10 +29,6 @@
 /* Define to the absolute path to the system regex.h */
 /* #undef TRE_SYSTEM_REGEX_H_PATH */
 
-/* Define if you want TRE to use alloca() instead of malloc() when allocating
-   memory needed for regexec operations. */
-#define TRE_USE_ALLOCA 1
-
 /* Define to include the system regex.h from TRE regex.h */
 /* #undef TRE_USE_SYSTEM_REGEX_H */