diff --git a/src/pcre2_compile.c b/src/pcre2_compile.c
index c414b62..f343047 100644
--- a/src/pcre2_compile.c
+++ b/src/pcre2_compile.c
@@ -5494,6 +5494,7 @@ for (;; pptr++)
   BOOL possessive_quantifier;
   BOOL note_group_empty;
   int class_has_8bitchar;
+  int i;
   uint32_t mclength;
   uint32_t skipunits;
   uint32_t subreqcu, subfirstcu;
@@ -5868,9 +5869,9 @@ for (;; pptr++)
         if (taboffset >= 0)
           {
           if (tabopt >= 0)
-            for (int i = 0; i < 32; i++) pbits[i] |= cbits[(int)i + taboffset];
+            for (i = 0; i < 32; i++) pbits[i] |= cbits[(int)i + taboffset];
           else
-            for (int i = 0; i < 32; i++) pbits[i] &= ~cbits[(int)i + taboffset];
+            for (i = 0; i < 32; i++) pbits[i] &= ~cbits[(int)i + taboffset];
           }
 
         /* Now see if we need to remove any special characters. An option
@@ -5884,9 +5885,9 @@ for (;; pptr++)
         being built and we are done. */
 
         if (local_negate)
-          for (int i = 0; i < 32; i++) classbits[i] |= (uint8_t)(~pbits[i]);
+          for (i = 0; i < 32; i++) classbits[i] |= (uint8_t)(~pbits[i]);
         else
-          for (int i = 0; i < 32; i++) classbits[i] |= pbits[i];
+          for (i = 0; i < 32; i++) classbits[i] |= pbits[i];
 
         /* Every class contains at least one < 256 character. */
 
@@ -5925,22 +5926,22 @@ for (;; pptr++)
         switch(escape)
           {
           case ESC_d:
-          for (int i = 0; i < 32; i++) classbits[i] |= cbits[i+cbit_digit];
+          for (i = 0; i < 32; i++) classbits[i] |= cbits[i+cbit_digit];
           break;
 
           case ESC_D:
           should_flip_negation = TRUE;
-          for (int i = 0; i < 32; i++)
+          for (i = 0; i < 32; i++)
             classbits[i] |= (uint8_t)(~cbits[i+cbit_digit]);
           break;
 
           case ESC_w:
-          for (int i = 0; i < 32; i++) classbits[i] |= cbits[i+cbit_word];
+          for (i = 0; i < 32; i++) classbits[i] |= cbits[i+cbit_word];
           break;
 
           case ESC_W:
           should_flip_negation = TRUE;
-          for (int i = 0; i < 32; i++)
+          for (i = 0; i < 32; i++)
             classbits[i] |= (uint8_t)(~cbits[i+cbit_word]);
           break;
 
@@ -5952,12 +5953,12 @@ for (;; pptr++)
           longer treat \s and \S specially. */
 
           case ESC_s:
-          for (int i = 0; i < 32; i++) classbits[i] |= cbits[i+cbit_space];
+          for (i = 0; i < 32; i++) classbits[i] |= cbits[i+cbit_space];
           break;
 
           case ESC_S:
           should_flip_negation = TRUE;
-          for (int i = 0; i < 32; i++)
+          for (i = 0; i < 32; i++)
             classbits[i] |= (uint8_t)(~cbits[i+cbit_space]);
           break;
 
@@ -6199,7 +6200,7 @@ for (;; pptr++)
         if (negate_class && !xclass_has_prop)
           {
           /* Using 255 ^ instead of ~ avoids clang sanitize warning. */
-          for (int i = 0; i < 32; i++) classbits[i] = 255 ^ classbits[i];
+          for (i = 0; i < 32; i++) classbits[i] = 255 ^ classbits[i];
           }
         memcpy(code, classbits, 32);
         code = class_uchardata + (32 / sizeof(PCRE2_UCHAR));
@@ -6225,7 +6226,7 @@ for (;; pptr++)
       if (negate_class)
         {
        /* Using 255 ^ instead of ~ avoids clang sanitize warning. */
-       for (int i = 0; i < 32; i++) classbits[i] = 255 ^ classbits[i];
+       for (i = 0; i < 32; i++) classbits[i] = 255 ^ classbits[i];
        }
       memcpy(code, classbits, 32);
       }
@@ -6299,7 +6300,7 @@ for (;; pptr++)
     verbarglen = *(++pptr);
     verbculen = 0;
     tempcode = code++;
-    for (int i = 0; i < (int)verbarglen; i++)
+    for (i = 0; i < (int)verbarglen; i++)
       {
       meta = *(++pptr);
 #ifdef SUPPORT_UNICODE
@@ -6772,6 +6773,7 @@ for (;; pptr++)
       BOOL is_dupname = FALSE;
       named_group *ng = cb->named_groups;
       uint32_t length = *(++pptr);
+      unsigned int i;
 
       GETPLUSOFFSET(offset, pptr);
       name = cb->start_pattern + offset;
@@ -6782,7 +6784,7 @@ for (;; pptr++)
       this name is duplicated. */
 
       groupnumber = 0;
-      for (unsigned int i = 0; i < cb->names_found; i++, ng++)
+      for (i = 0; i < cb->names_found; i++, ng++)
         {
         if (length == ng->length &&
             PRIV(strncmp)(name, ng->name, length) == 0)
@@ -7141,7 +7143,7 @@ for (;; pptr++)
           *lengthptr += delta;
           }
 
-        else for (int i = 0; i < replicate; i++)
+        else for (i = 0; i < replicate; i++)
           {
           memcpy(code, previous, CU2BYTES(1 + LINK_SIZE));
           previous = code;
@@ -7317,12 +7319,13 @@ for (;; pptr++)
 
             else
               {
+              uint32_t i;
               if (groupsetfirstcu && reqcuflags >= REQ_NONE)
                 {
                 reqcu = firstcu;
                 reqcuflags = firstcuflags;
                 }
-              for (uint32_t i = 1; i < repeat_min; i++)
+              for (i = 1; i < repeat_min; i++)
                 {
                 memcpy(code, previous, CU2BYTES(len));
                 code += len;
@@ -7342,6 +7345,7 @@ for (;; pptr++)
 
         if (repeat_max != REPEAT_UNLIMITED)
           {
+          uint32_t i;
           /* In the pre-compile phase, we don't actually do the replication. We
           just adjust the length as if we had. For each repetition we must add
           1 to the length for BRAZERO and for all but the last repetition we
@@ -7366,7 +7370,7 @@ for (;; pptr++)
 
           /* This is compiling for real */
 
-          else for (uint32_t i = repeat_max; i >= 1; i--)
+          else for (i = repeat_max; i >= 1; i--)
             {
             *code++ = OP_BRAZERO + repeat_type;
 
diff --git a/src/pcre2_printint.c b/src/pcre2_printint.c
index 3b6a07d..46b9038 100644
--- a/src/pcre2_printint.c
+++ b/src/pcre2_printint.c
@@ -244,8 +244,9 @@ int count = 0;
 const char *yield = "??";
 size_t len = 0;
 unsigned int ptypex = (ptype == PT_SC)? PT_SCX : ptype;
+int i;
 
-for (int i = PRIV(utt_size) - 1; i >= 0; i--)
+for (i = PRIV(utt_size) - 1; i >= 0; i--)
   {
   const ucp_type_table *u = PRIV(utt) + i;
 
diff --git a/src/pcre2_script_run.c b/src/pcre2_script_run.c
index 4926fa6..6d7e830 100644
--- a/src/pcre2_script_run.c
+++ b/src/pcre2_script_run.c
@@ -90,6 +90,7 @@ uint32_t require_map[FULL_MAPSIZE];
 uint32_t map[FULL_MAPSIZE];
 uint32_t require_digitset = 0;
 uint32_t c;
+int i;
 
 #if PCRE2_CODE_UNIT_WIDTH == 32
 (void)utf;    /* Avoid compiler warning */
@@ -106,7 +107,7 @@ every script, as opposed to the maps in ucd_script_sets, which only have bits
 for scripts less than ucp_Unknown - those that appear in script extension
 lists. */
 
-for (int i = 0; i < FULL_MAPSIZE; i++) require_map[i] = 0;
+for (i = 0; i < FULL_MAPSIZE; i++) require_map[i] = 0;
 
 /* Scan strings of two or more characters, checking the Unicode characteristics
 of each code point. There is special code for scripts that can be combined with
@@ -245,7 +246,7 @@ for (;;)
       case SCRIPT_MAP:
       OK = FALSE;
 
-      for (int i = 0; i < FULL_MAPSIZE; i++)
+      for (i = 0; i < FULL_MAPSIZE; i++)
         {
         if ((require_map[i] & map[i]) != 0)
           {
@@ -282,7 +283,7 @@ for (;;)
         allowed scripts for this character. */
 
         default:
-        for (int i = 0; i < FULL_MAPSIZE; i++) require_map[i] &= map[i];
+        for (i = 0; i < FULL_MAPSIZE; i++) require_map[i] &= map[i];
         break;
         }
 
diff --git a/src/pcre2test.c b/src/pcre2test.c
index 7349473..0904fd7 100644
--- a/src/pcre2test.c
+++ b/src/pcre2test.c
@@ -8462,13 +8462,14 @@ int count;
 int maxi = 0;
 const char *maxs = "";
 size_t max = 0;
+int i;
 
 for (count = 0; ff[count] >= 0; count++) {}
 
 /* Find the name to put first. For scripts, any 3-character name is chosen.
 For non-scripts, or if there is no 3-character name, take the longest. */
 
-for (int i = 0; ff[i] >= 0; i++)
+for (i = 0; ff[i] >= 0; i++)
   {
   const char *s = PRIV(utt_names) + ff[i];
   size_t len = strlen(s);
@@ -8493,7 +8494,7 @@ buff += max;
 if (count > 1)
   {
   const char *sep = " (";
-  for (int i = 0; i < count; i++)
+  for (i = 0; i < count; i++)
     {
     if (i == maxi) continue;
     buff += sprintf(buff, "%s%s", sep, PRIV(utt_names) + ff[i]);
@@ -8528,6 +8529,8 @@ int16_t found[256][MAX_SYNONYMS + 1];
 int fc = 0;
 int colwidth = 40;
 int n;
+size_t i, j;
+int k;
 
 if (wantscripts)
   {
@@ -8540,7 +8543,7 @@ else
   typename = "PROPERTIES";
   }
 
-for (size_t i = 0; i < PRIV(utt_size); i++)
+for (i = 0; i < PRIV(utt_size); i++)
   {
   int k;
   int m = 0;
@@ -8569,7 +8572,7 @@ for (size_t i = 0; i < PRIV(utt_size); i++)
   fv = found[fc++];
   fv[m++] = t->name_offset;
 
-  for (size_t j = i + 1; j < PRIV(utt_size); j++)
+  for (j = i + 1; j < PRIV(utt_size); j++)
     {
     const ucp_type_table *tt = PRIV(utt) + j;
     if (tt->type != t->type || tt->value != value) continue;
@@ -8591,7 +8594,7 @@ if (!wantscripts) printf(
 "and the following binary (yes/no) properties:\n\n");
 
 
-for (int k = 0; k < (n+1)/2; k++)
+for (k = 0; k < (n+1)/2; k++)
   {
   int x;
   char buff1[128];
@@ -8621,8 +8624,9 @@ display_one_modifier(modstruct *m, BOOL for_pattern)
 {
 uint32_t c = (!for_pattern && (m->which == MOD_PND || m->which == MOD_PNDP))?
   '*' : ' ';
+size_t i;
 printf("%c%s", c, m->name);
-for (size_t i = 0; i < C1MODLISTCOUNT; i++)
+for (i = 0; i < C1MODLISTCOUNT; i++)
   {
   if (strcmp(m->name, c1modlist[i].fullname) == 0)
     printf(" (%c)", c1modlist[i].onechar);
@@ -8687,8 +8691,9 @@ for (i = 0; i < MODLISTCOUNT; i++)
 
   if (for_pattern == is_pattern)
     {
+    size_t k;
     extra[n] = 0;
-    for (size_t k = 0; k < C1MODLISTCOUNT; k++)
+    for (k = 0; k < C1MODLISTCOUNT; k++)
       {
       if (strcmp(m->name, c1modlist[k].fullname) == 0)
         {