PR fortran/95689 - ICE in check_sym_interfaces, at fortran/interface.c:2015

With submodules, name mangling of interfaces may result in long internal
symbols overflowing an internal buffer.  We now check that we do not
exceed the enlarged buffer size.

gcc/fortran/
	PR fortran/95689
	* interface.c (check_sym_interfaces): Enlarge temporary buffer,
	and add check on length on mangled name to prevent overflow.

(cherry picked from commit 62c0c0ea7bfb6f8f6b8d767b05120cafb6823da6)

gcc/fortran/interface.c

@@ -1981,7 +1981,8 @@ check_interface1 (gfc_interface *p, gfc_interface *q0,
 static void
 check_sym_interfaces (gfc_symbol *sym)
 {
-  char interface_name[GFC_MAX_SYMBOL_LEN + sizeof("generic interface ''")];
+  /* Provide sufficient space to hold "generic interface 'symbol.symbol'".  */
+  char interface_name[2*GFC_MAX_SYMBOL_LEN+2 + sizeof("generic interface ''")];
   gfc_interface *p;
 
   if (sym->ns != gfc_current_ns)
@@ -1989,6 +1990,8 @@ check_sym_interfaces (gfc_symbol *sym)
 
   if (sym->generic != NULL)
     {
+      size_t len = strlen (sym->name) + sizeof("generic interface ''");
+      gcc_assert (len < sizeof (interface_name));
       sprintf (interface_name, "generic interface '%s'", sym->name);
       if (check_interface0 (sym->generic, interface_name))
 	return;

gcc/testsuite/gfortran.dg/pr95689.f90

+! { dg-do compile }
+! { dg-options "-fsecond-underscore" }
+! PR fortran/95689 - ICE in check_sym_interfaces, at fortran/interface.c:2015
+
+module m2345678901234567890123456789012345678901234567890123456789_123
+  type t2345678901234567890123456789012345678901234567890123456789_123
+   end type
+   interface
+      module subroutine s2345678901234567890123456789012345678901234567890123456789_123 &
+                       (x2345678901234567890123456789012345678901234567890123456789_123)
+      end
+   end interface
+end
+submodule(m2345678901234567890123456789012345678901234567890123456789_123) &
+          t2345678901234567890123456789012345678901234567890123456789_123
+end