Revert fixes to allocation of regex matching

The fix was not complete, and completing it was proving too complicated.

- Revert "* src/regex.c (re_search_2): Make new code safe for
          -Wjump-misses-init."
  This reverts commit c2a17924a57483d14692c8913edbe8ad24b5ffbb.
- Revert "Port to GCC 6.2.1 + --enable-gcc-warnings"
  This reverts commit f6134bbda259c115c06d4a9a3ab5c39340a15949.
- Revert "Fix handling of allocation in regex matching"
  This reverts commit ad66b3fadb7ae22a4cbb82bb1507c39ceadf3897.
- Revert "Fix handling of buffer relocation in regex.c functions"
  This reverts commit ee04aedc723b035eedaf975422d4eb242894121b.

4 files changed, 14 insertions, 107 deletions

diff --git a/src/dired.c b/src/dired.c
index 006f74c834d..dba575ce4c2 100644
--- a/src/dired.c
+++ b/src/dired.c
@@ -259,11 +259,9 @@ directory_files_internal (Lisp_Object directory, Lisp_Object full,
       QUIT;
 
       bool wanted = (NILP (match)
-                     || (re_match_object = name,
-                         re_search (bufp, SSDATA (name), len, 0, len, 0) >= 0));
+                     || re_search (bufp, SSDATA (name), len, 0, len, 0) >= 0);
 
       immediate_quit = 0;
-      re_match_object = Qnil;   /* Stop protecting name from GC.  */
 
       if (wanted)
         {
diff --git a/src/regex.c b/src/regex.c
index b12e95b38c0..56b18e6b5bb 100644
--- a/src/regex.c
+++ b/src/regex.c
@@ -1438,62 +1438,11 @@ typedef struct
 #define NEXT_FAILURE_HANDLE(h) fail_stack.stack[(h) - 3].integer
 #define TOP_FAILURE_HANDLE() fail_stack.frame
 
-#ifdef emacs
-# define STR_BASE_PTR(obj)                       \
-   (NILP (obj) ? current_buffer->text->beg       \
-    : STRINGP (obj) ? SDATA (obj)                \
-    : NULL)
-#else
-# define STR_BASE_PTR(obj) NULL
-#endif
 
 #define ENSURE_FAIL_STACK(space)                                        \
 while (REMAINING_AVAIL_SLOTS <= space) {                                \
-  re_char *orig_base = STR_BASE_PTR (re_match_object);                  \
-  bool might_relocate = orig_base != NULL;                              \
-  ptrdiff_t string1_off, end1_off, end_match_1_off;                     \
-  ptrdiff_t string2_off, end2_off, end_match_2_off;                     \
-  ptrdiff_t d_off, dend_off, dfail_off;                                 \
-  if (might_relocate)                                                   \
-    {                                                                   \
-      if (string1)                                                      \
-        {                                                               \
-          string1_off = string1 - orig_base;                            \
-          end1_off = end1 - orig_base;                                  \
-          end_match_1_off = end_match_1 - orig_base;                    \
-        }                                                               \
-      if (string2)                                                      \
-        {                                                               \
-          string2_off = string2 - orig_base;                            \
-          end2_off = end2 - orig_base;                                  \
-          end_match_2_off = end_match_2 - orig_base;                    \
-        }                                                               \
-      d_off = d - orig_base;                                            \
-      dend_off = dend - orig_base;                                      \
-      dfail_off = dfail - orig_base;                                    \
-    }                                                                   \
   if (!GROW_FAIL_STACK (fail_stack))                                    \
     return -2;                                                          \
-  /* In Emacs, GROW_FAIL_STACK might relocate string pointers.  */      \
-  if (might_relocate)                                                   \
-    {                                                                   \
-      re_char *new_base = STR_BASE_PTR (re_match_object);               \
-      if (string1)                                                      \
-        {                                                               \
-          string1 = new_base + string1_off;                             \
-          end1 = new_base + end1_off;                                   \
-          end_match_1 = new_base + end_match_1_off;                     \
-        }                                                               \
-      if (string2)                                                      \
-        {                                                               \
-          string2 = new_base + string2_off;                             \
-          end2 = new_base + end2_off;                                   \
-          end_match_2 = new_base + end_match_2_off;                     \
-        }                                                               \
-      d = new_base + d_off;                                             \
-      dend = new_base + dend_off;                                       \
-      dfail = new_base + dfail_off;                                     \
-    }                                                                   \
   DEBUG_PRINT ("\n  Doubled stack; size now: %zd\n", (fail_stack).size);\
   DEBUG_PRINT ("         slots available: %zd\n", REMAINING_AVAIL_SLOTS);\
 }
@@ -4380,10 +4329,6 @@ re_search_2 (struct re_pattern_buffer *bufp, const char *str1, size_t size1,
   /* Loop through the string, looking for a place to start matching.  */
   for (;;)
     {
-      ptrdiff_t offset1, offset2;
-      re_char *orig_base;
-      bool might_relocate;
-
       /* If the pattern is anchored,
          skip quickly past places we cannot match.
          We don't bother to treat startpos == 0 specially
@@ -4500,17 +4445,6 @@ re_search_2 (struct re_pattern_buffer *bufp, const char *str1, size_t size1,
           && !bufp->can_be_null)
         return -1;
 
-      /* re_match_2_internal may allocate, relocating the Lisp text
-         object that we're searching.  */
-      IF_LINT (offset2 = 0);  /* Work around GCC bug 78081.  */
-      orig_base = STR_BASE_PTR (re_match_object);
-      might_relocate = orig_base != NULL;
-      if (might_relocate)
-        {
-          if (string1) offset1 = string1 - orig_base;
-          if (string2) offset2 = string2 - orig_base;
-        }
-
       val = re_match_2_internal (bufp, string1, size1, string2, size2,
                                  startpos, regs, stop);
 
@@ -4520,13 +4454,6 @@ re_search_2 (struct re_pattern_buffer *bufp, const char *str1, size_t size1,
       if (val == -2)
         return -2;
 
-      if (might_relocate)
-        {
-          re_char *new_base = STR_BASE_PTR (re_match_object);
-          if (string1) string1 = offset1 + new_base;
-          if (string2) string2 = offset2 + new_base;
-        }
-
     advance:
       if (!range)
         break;
diff --git a/src/regex.h b/src/regex.h
index 61c771c045f..51f4424ce94 100644
--- a/src/regex.h
+++ b/src/regex.h
@@ -169,9 +169,7 @@ extern reg_syntax_t re_syntax_options;
 #ifdef emacs
 # include "lisp.h"
 /* In Emacs, this is the string or buffer in which we are matching.
-   It is used for looking up syntax properties, and also to recompute
-   pointers in case the object is relocated as a side effect of
-   calling malloc (if it calls r_alloc_sbrk in ralloc.c).
+   It is used for looking up syntax properties.
 
    If the value is a Lisp string object, we are matching text in that
    string; if it's nil, we are matching text in the current buffer; if
diff --git a/src/search.c b/src/search.c
index b50e7f032d5..fa5ac44de9d 100644
--- a/src/search.c
+++ b/src/search.c
@@ -287,10 +287,8 @@ looking_at_1 (Lisp_Object string, bool posix)
   immediate_quit = 1;
   QUIT;                 /* Do a pending quit right away, to avoid paradoxical behavior */
 
-  /* Get pointers and sizes of the two strings that make up the
-     visible portion of the buffer.  Note that we can use pointers
-     here, unlike in search_buffer, because we only call re_match_2
-     once, after which we never use the pointers again.  */
+  /* Get pointers and sizes of the two strings
+     that make up the visible portion of the buffer. */
 
   p1 = BEGV_ADDR;
   s1 = GPT_BYTE - BEGV_BYTE;
@@ -409,7 +407,6 @@ string_match_1 (Lisp_Object regexp, Lisp_Object string, Lisp_Object start,
                    (NILP (Vinhibit_changing_match_data)
                     ? &search_regs : NULL));
   immediate_quit = 0;
-  re_match_object = Qnil;       /* Stop protecting string from GC.  */
 
   /* Set last_thing_searched only when match data is changed.  */
   if (NILP (Vinhibit_changing_match_data))
@@ -480,7 +477,6 @@ fast_string_match_internal (Lisp_Object regexp, Lisp_Object string,
                    SBYTES (string), 0,
                    SBYTES (string), 0);
   immediate_quit = 0;
-  re_match_object = Qnil;       /* Stop protecting string from GC.  */
   return val;
 }
 
@@ -568,7 +564,6 @@ fast_looking_at (Lisp_Object regexp, ptrdiff_t pos, ptrdiff_t pos_byte,
   len = re_match_2 (buf, (char *) p1, s1, (char *) p2, s2,
                     pos_byte, NULL, limit_byte);
   immediate_quit = 0;
-  re_match_object = Qnil;       /* Stop protecting string from GC.  */
 
   return len;
 }
@@ -1183,8 +1178,8 @@ search_buffer (Lisp_Object string, ptrdiff_t pos, ptrdiff_t pos_byte,
 
   if (RE && !(trivial_regexp_p (string) && NILP (Vsearch_spaces_regexp)))
     {
-      unsigned char *base;
-      ptrdiff_t off1, off2, s1, s2;
+      unsigned char *p1, *p2;
+      ptrdiff_t s1, s2;
       struct re_pattern_buffer *bufp;
 
       bufp = compile_pattern (string,
@@ -1198,19 +1193,16 @@ search_buffer (Lisp_Object string, ptrdiff_t pos, ptrdiff_t pos_byte,
                                    can take too long. */
       QUIT;                     /* Do a pending quit right away,
                                    to avoid paradoxical behavior */
-      /* Get offsets and sizes of the two strings that make up the
-         visible portion of the buffer.  We compute offsets instead of
-         pointers because re_search_2 may call malloc and therefore
-         change the buffer text address.  */
+      /* Get pointers and sizes of the two strings
+         that make up the visible portion of the buffer. */
 
-      base = current_buffer->text->beg;
-      off1 = BEGV_ADDR - base;
+      p1 = BEGV_ADDR;
       s1 = GPT_BYTE - BEGV_BYTE;
-      off2 = GAP_END_ADDR - base;
+      p2 = GAP_END_ADDR;
       s2 = ZV_BYTE - GPT_BYTE;
       if (s1 < 0)
         {
-          off2 = off1;
+          p2 = p1;
           s2 = ZV_BYTE - BEGV_BYTE;
           s1 = 0;
         }
@@ -1225,16 +1217,12 @@ search_buffer (Lisp_Object string, ptrdiff_t pos, ptrdiff_t pos_byte,
         {
           ptrdiff_t val;
 
-          val = re_search_2 (bufp,
-                             (char*) (base + off1), s1,
-                             (char*) (base + off2), s2,
+          val = re_search_2 (bufp, (char *) p1, s1, (char *) p2, s2,
                              pos_byte - BEGV_BYTE, lim_byte - pos_byte,
                              (NILP (Vinhibit_changing_match_data)
                               ? &search_regs : &search_regs_1),
                              /* Don't allow match past current point */
                              pos_byte - BEGV_BYTE);
-          /* Update 'base' due to possible relocation inside re_search_2.  */
-          base = current_buffer->text->beg;
           if (val == -2)
             {
               matcher_overflow ();
@@ -1274,15 +1262,11 @@ search_buffer (Lisp_Object string, ptrdiff_t pos, ptrdiff_t pos_byte,
         {
           ptrdiff_t val;
 
-          val = re_search_2 (bufp,
-                             (char*) (base + off1), s1,
-                             (char*) (base + off2), s2,
-                             pos_byte - BEGV_BYTE, lim_byte - pos_byte,
+          val = re_search_2 (bufp, (char *) p1, s1, (char *) p2, s2,
+                             pos_byte - BEGV_BYTE, lim_byte - pos_byte,
                              (NILP (Vinhibit_changing_match_data)
                               ? &search_regs : &search_regs_1),
                              lim_byte - BEGV_BYTE);
-          /* Update 'base' due to possible relocation inside re_search_2.  */
-          base = current_buffer->text->beg;
           if (val == -2)
             {
               matcher_overflow ();