--- gcc/gcc/doc/invoke.texi
+++ gcc/gcc/doc/invoke.texi
@@ -12842,6 +12842,10 @@ allocations.  @option{-fstack-clash-protection} may also provide limited
 protection for static stack allocations if the target supports
 @option{-fstack-check=specific}.
 
+NOTE: In ALT gcc 10.2.1-alt1 and later versions this option is enabled by
+default for C, C++, ObjC, ObjC++ if @option{-fno-stack-clash-protection}
+is not specified.
+
 @item -fstack-limit-register=@var{reg}
 @itemx -fstack-limit-symbol=@var{sym}
 @itemx -fno-stack-limit
--- gcc/gcc/gcc.c
+++ gcc/gcc/gcc.c
@@ -1146,6 +1146,7 @@ static const char *cpp_debug_options = "%{d*}";
 static const char *cc1_options =
 "%{pg:%{fomit-frame-pointer:%e-pg and -fomit-frame-pointer are incompatible}}\
  %{!fno-stack-protector:%{!fstack-protector:%{!fstack-protector-strong:%{!fstack-protector-all:%{!fstack-protector-explicit:%{!ffreestanding:%{!nostdlib:-fstack-protector-strong}}}}}}}\
+ %{!fno-stack-clash-protection:%{!fstack-clash-protection:-fstack-clash-protection}}\
  %{!iplugindir*:%{fplugin*:%:find-plugindir()}}\
  %1 %{!Q:-quiet} %{!dumpbase:-dumpbase %B} %{d*} %{m*} %{aux-info*}\
  %{fcompare-debug-second:%:compare-debug-auxbase-opt(%b)} \