diff --git a/libiberty/ChangeLog b/libiberty/ChangeLog
index 95cb1525f2..085b7b3fbf 100644
--- a/libiberty/ChangeLog
+++ b/libiberty/ChangeLog
@@ -1,3 +1,8 @@
+2019-11-16  Tim Ruehsen  <tim.ruehsen@gmx.de>
+
+	* cplus-dem.c (ada_demangle): Correctly calculate the demangled
+	size by using two passes. Fixes #92453.
+
 2019-08-08  Martin Liska  <mliska@suse.cz>

 	PR bootstrap/91352
diff --git a/libiberty/cplus-dem.c b/libiberty/cplus-dem.c
index a39e2bf2ed..be76e691b0 100644
--- a/libiberty/cplus-dem.c
+++ b/libiberty/cplus-dem.c
@@ -230,7 +230,7 @@ rust_demangle (const char *mangled, int options)
 char *
 ada_demangle (const char *mangled, int option ATTRIBUTE_UNUSED)
 {
-  int len0;
+  int len0 = 0, run;
   const char* p;
   char *d;
   char *demangled = NULL;
@@ -243,236 +243,270 @@ ada_demangle (const char *mangled, int option ATTRIBUTE_UNUSED)
   if (!ISLOWER (mangled[0]))
     goto unknown;

-  /* Most of the demangling will trivially remove chars.  Operator names
-     may add one char but because they are always preceeded by '__' which is
-     replaced by '.', they eventually never expand the size.
-     A few special names such as '___elabs' add a few chars (at most 7), but
-     they occur only once.  */
-  len0 = strlen (mangled) + 7 + 1;
-  demangled = XNEWVEC (char, len0);
-
-  d = demangled;
-  p = mangled;
-  while (1)
+  for (run = 0; run <= 1; run++)
     {
-      /* An entity names is expected.  */
-      if (ISLOWER (*p))
+      if (run == 1)
         {
-          /* An identifier, which is always lower case.  */
-          do
-            *d++ = *p++;
-          while (ISLOWER(*p) || ISDIGIT (*p)
-                 || (p[0] == '_' && (ISLOWER (p[1]) || ISDIGIT (p[1]))));
+          demangled = XNEWVEC (char, len0 + 1);
         }
-      else if (p[0] == 'O')
+
+      p = mangled;
+      d = demangled;
+
+      while (1)
         {
-          /* An operator name.  */
-          static const char * const operators[][2] =
-            {{"Oabs", "abs"},  {"Oand", "and"},    {"Omod", "mod"},
-             {"Onot", "not"},  {"Oor", "or"},      {"Orem", "rem"},
-             {"Oxor", "xor"},  {"Oeq", "="},       {"One", "/="},
-             {"Olt", "<"},     {"Ole", "<="},      {"Ogt", ">"},
-             {"Oge", ">="},    {"Oadd", "+"},      {"Osubtract", "-"},
-             {"Oconcat", "&"}, {"Omultiply", "*"}, {"Odivide", "/"},
-             {"Oexpon", "**"}, {NULL, NULL}};
-          int k;
-
-          for (k = 0; operators[k][0] != NULL; k++)
+          /* An entity names is expected.  */
+          if (ISLOWER (*p))
             {
-              size_t slen = strlen (operators[k][0]);
-              if (strncmp (p, operators[k][0], slen) == 0)
+              /* An identifier, which is always lower case.  */
+              do
+                run ? (*d++ = *p++) : (p++, len0++);
+              while (ISLOWER (*p) || ISDIGIT (*p)
+                     || (p[0] == '_' && (ISLOWER (p[1]) || ISDIGIT (p[1]))));
+            }
+          else if (p[0] == 'O')
+            {
+              /* An operator name.  */
+              static const char * const operators[][2] ={
+                {"Oabs", "abs"},
+                {"Oand", "and"},
+                {"Omod", "mod"},
+                {"Onot", "not"},
+                {"Oor", "or"},
+                {"Orem", "rem"},
+                {"Oxor", "xor"},
+                {"Oeq", "="},
+                {"One", "/="},
+                {"Olt", "<"},
+                {"Ole", "<="},
+                {"Ogt", ">"},
+                {"Oge", ">="},
+                {"Oadd", "+"},
+                {"Osubtract", "-"},
+                {"Oconcat", "&"},
+                {"Omultiply", "*"},
+                {"Odivide", "/"},
+                {"Oexpon", "**"},
+                {NULL, NULL}};
+              int k;
+
+              for (k = 0; operators[k][0] != NULL; k++)
                 {
-                  p += slen;
-                  slen = strlen (operators[k][1]);
-                  *d++ = '"';
-                  memcpy (d, operators[k][1], slen);
-                  d += slen;
-                  *d++ = '"';
-                  break;
+                  size_t slen = strlen (operators[k][0]);
+                  if (strncmp (p, operators[k][0], slen) == 0)
+                    {
+                      p += slen;
+                      slen = strlen (operators[k][1]);
+                      if (run)
+                        {
+                          *d++ = '"';
+                          memcpy (d, operators[k][1], slen);
+                          d += slen;
+                          *d++ = '"';
+                        }
+                      else
+                        len0 += slen + 2;
+                      break;
+                    }
                 }
+              /* Operator not found.  */
+              if (operators[k][0] == NULL)
+                goto unknown;
             }
-          /* Operator not found.  */
-          if (operators[k][0] == NULL)
-            goto unknown;
-        }
-      else
-        {
-          /* Not a GNAT encoding.  */
-          goto unknown;
-        }
-
-      /* The name can be directly followed by some uppercase letters.  */
-      if (p[0] == 'T' && p[1] == 'K')
-        {
-          /* Task stuff.  */
-          if (p[2] == 'B' && p[3] == 0)
+          else
             {
-              /* Subprogram for task body.  */
-              break;
+              /* Not a GNAT encoding.  */
+              goto unknown;
             }
-          else if (p[2] == '_' && p[3] == '_')
+
+          /* The name can be directly followed by some uppercase letters.  */
+          if (p[0] == 'T' && p[1] == 'K')
             {
-              /* Inner declarations in a task.  */
-              p += 4;
-              *d++ = '.';
-              continue;
+              /* Task stuff.  */
+              if (p[2] == 'B' && p[3] == 0)
+                {
+                  /* Subprogram for task body.  */
+                  break;
+                }
+              else if (p[2] == '_' && p[3] == '_')
+                {
+                  /* Inner declarations in a task.  */
+                  p += 4;
+                  run ? *d++ = '.' : len0++;
+                  continue;
+                }
+              else
+                goto unknown;
             }
-          else
-            goto unknown;
-        }
-      if (p[0] == 'E' && p[1] == 0)
-        {
-          /* Exception name.  */
-          goto unknown;
-        }
-      if ((p[0] == 'P' || p[0] == 'N') && p[1] == 0)
-        {
-          /* Protected type subprogram.  */
-          break;
-        }
-      if ((*p == 'N' || *p == 'S') && p[1] == 0)
-        {
-          /* Enumerated type name table.  */
-          goto unknown;
-        }
-      if (p[0] == 'X')
-        {
-          /* Body nested.  */
-          p++;
-          while (p[0] == 'n' || p[0] == 'b')
-            p++;
-        }
-      if (p[0] == 'S' && p[1] != 0 && (p[2] == '_' || p[2] == 0))
-        {
-          /* Stream operations.  */
-          const char *name;
-          switch (p[1])
+          if (p[0] == 'E' && p[1] == 0)
             {
-            case 'R':
-              name = "'Read";
-              break;
-            case 'W':
-              name = "'Write";
-              break;
-            case 'I':
-              name = "'Input";
-              break;
-            case 'O':
-              name = "'Output";
-              break;
-            default:
+              /* Exception name.  */
               goto unknown;
             }
-          p += 2;
-          strcpy (d, name);
-          d += strlen (name);
-        }
-      else if (p[0] == 'D')
-        {
-          /* Controlled type operation.  */
-          const char *name;
-          switch (p[1])
+          if ((p[0] == 'P' || p[0] == 'N') && p[1] == 0)
             {
-            case 'F':
-              name = ".Finalize";
-              break;
-            case 'A':
-              name = ".Adjust";
+              /* Protected type subprogram.  */
               break;
-            default:
+            }
+          if ((*p == 'N' || *p == 'S') && p[1] == 0)
+            {
+              /* Enumerated type name table.  */
               goto unknown;
             }
-          strcpy (d, name);
-          d += strlen (name);
-          break;
-        }
-
-      if (p[0] == '_')
-        {
-          /* Separator.  */
-          if (p[1] == '_')
+          if (p[0] == 'X')
+            {
+              /* Body nested.  */
+              p++;
+              while (p[0] == 'n' || p[0] == 'b')
+                p++;
+            }
+          if (p[0] == 'S' && p[1] != 0 && (p[2] == '_' || p[2] == 0))
             {
-              /* Standard separator.  Handled first.  */
+              /* Stream operations.  */
+              const char *name;
+              switch (p[1])
+                {
+                case 'R':
+                  name = "'Read";
+                  break;
+                case 'W':
+                  name = "'Write";
+                  break;
+                case 'I':
+                  name = "'Input";
+                  break;
+                case 'O':
+                  name = "'Output";
+                  break;
+                default:
+                  goto unknown;
+                }
               p += 2;
+              if (run)
+                {
+                  strcpy (d, name);
+                  d += strlen (name);
+                }
+              else
+                len0 += strlen (name);
+            }
+          else if (p[0] == 'D')
+            {
+              /* Controlled type operation.  */
+              const char *name;
+              switch (p[1])
+                {
+                case 'F':
+                  name = ".Finalize";
+                  break;
+                case 'A':
+                  name = ".Adjust";
+                  break;
+                default:
+                  goto unknown;
+                }
+              if (run)
+                {
+                  strcpy (d, name);
+                  d += strlen (name);
+                }
+              else
+                len0 += strlen (name);
+              break;
+            }

-              if (ISDIGIT (*p))
+          if (p[0] == '_')
+            {
+              /* Separator.  */
+              if (p[1] == '_')
                 {
-                  /* Overloading number.  */
-                  do
-                    p++;
-                  while (ISDIGIT (*p) || (p[0] == '_' && ISDIGIT (p[1])));
-                  if (*p == 'X')
+                  /* Standard separator.  Handled first.  */
+                  p += 2;
+
+                  if (ISDIGIT (*p))
                     {
-                      p++;
-                      while (p[0] == 'n' || p[0] == 'b')
+                      /* Overloading number.  */
+                      do
                         p++;
+                      while (ISDIGIT (*p) || (p[0] == '_' && ISDIGIT (p[1])));
+                      if (*p == 'X')
+                        {
+                          p++;
+                          while (p[0] == 'n' || p[0] == 'b')
+                            p++;
+                        }
                     }
-                }
-              else if (p[0] == '_' && p[1] != '_')
-                {
-                  /* Special names.  */
-                  static const char * const special[][2] = {
-                    { "_elabb", "'Elab_Body" },
-                    { "_elabs", "'Elab_Spec" },
-                    { "_size", "'Size" },
-                    { "_alignment", "'Alignment" },
-                    { "_assign", ".\":=\"" },
-                    { NULL, NULL }
-                  };
-                  int k;
-
-                  for (k = 0; special[k][0] != NULL; k++)
+                  else if (p[0] == '_' && p[1] != '_')
                     {
-                      size_t slen = strlen (special[k][0]);
-                      if (strncmp (p, special[k][0], slen) == 0)
+                      /* Special names.  */
+                      static const char * const special[][2] = {
+                        { "_elabb", "'Elab_Body"},
+                        { "_elabs", "'Elab_Spec"},
+                        { "_size", "'Size"},
+                        { "_alignment", "'Alignment"},
+                        { "_assign", ".\":=\""},
+                        { NULL, NULL}
+                      };
+                      int k;
+
+                      for (k = 0; special[k][0] != NULL; k++)
                         {
-                          p += slen;
-                          slen = strlen (special[k][1]);
-                          memcpy (d, special[k][1], slen);
-                          d += slen;
-                          break;
+                          size_t slen = strlen (special[k][0]);
+                          if (strncmp (p, special[k][0], slen) == 0)
+                            {
+                              p += slen;
+                              slen = strlen (special[k][1]);
+                              if (run)
+                                {
+                                  memcpy (d, special[k][1], slen);
+                                  d += slen;
+                                }
+                              else
+                                len0 += slen;
+                              break;
+                            }
                         }
+                      if (special[k][0] != NULL)
+                        break;
+                      else
+                        goto unknown;
+                    }
+                  else
+                    {
+                      run ? *d++ = '.' : len0++;
+                      continue;
                     }
-                  if (special[k][0] != NULL)
+                }
+              else if (p[1] == 'B' || p[1] == 'E')
+                {
+                  /* Entry Body or barrier Evaluation.  */
+                  p += 2;
+                  while (ISDIGIT (*p))
+                    p++;
+                  if (p[0] == 's' && p[1] == 0)
                     break;
                   else
                     goto unknown;
                 }
               else
-                {
-                  *d++ = '.';
-                  continue;
-                }
+                goto unknown;
             }
-          else if (p[1] == 'B' || p[1] == 'E')
+
+          if (p[0] == '.' && ISDIGIT (p[1]))
             {
-              /* Entry Body or barrier Evaluation.  */
+              /* Nested subprogram.  */
               p += 2;
               while (ISDIGIT (*p))
                 p++;
-              if (p[0] == 's' && p[1] == 0)
-                break;
-              else
-                goto unknown;
+            }
+          if (*p == 0)
+            {
+              /* End of mangled name.  */
+              break;
             }
           else
             goto unknown;
         }
-
-      if (p[0] == '.' && ISDIGIT (p[1]))
-        {
-          /* Nested subprogram.  */
-          p += 2;
-          while (ISDIGIT (*p))
-            p++;
-        }
-      if (*p == 0)
-        {
-          /* End of mangled name.  */
-          break;
-        }
-      else
-        goto unknown;
     }
   *d = 0;
   return demangled;
