[Ada] Clarify hardening command-line options that require explicit choices

[Pierre-Marie de Rodat <derodat@adacore.com>]

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Prefixes -fzero-call-used-regs and -fstrub could be mistaken for full
command-line options with the references to them in the GNAT RM.  Make
it clearer that they require explicit choices.

Tested on x86_64-pc-linux-gnu, committed on trunk

gcc/ada/

	* doc/gnat_rm/security_hardening_features.rst: Clarify the need
	for choices after -fzero-call-used-regs and -fstrub.
	* gnat_rm.texi: Regenerate.

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diff --git a/gcc/ada/doc/gnat_rm/security_hardening_features.rst b/gcc/ada/doc/gnat_rm/security_hardening_features.rst
--- a/gcc/ada/doc/gnat_rm/security_hardening_features.rst
+++ b/gcc/ada/doc/gnat_rm/security_hardening_features.rst
@@ -18,9 +18,10 @@ Register Scrubbing
 GNAT can generate code to zero-out hardware registers before returning
 from a subprogram.
 
-It can be enabled with the :switch:`-fzero-call-used-regs` command-line
-option, to affect all subprograms in a compilation, and with a
-:samp:`Machine_Attribute` pragma, to affect only specific subprograms.
+It can be enabled with the :switch:`-fzero-call-used-regs={choice}`
+command-line option, to affect all subprograms in a compilation, and
+with a :samp:`Machine_Attribute` pragma, to affect only specific
+subprograms.
 
 .. code-block:: ada
 
@@ -73,11 +74,11 @@ or a variable.)
      --  scrubbing of the stack space used by that subprogram.
 
 
-There are also :switch:`-fstrub` command-line options to control
-default settings.  For usage and more details on the command-line
-option, on the ``strub`` attribute, and their use with other
-programming languages, see :title:`Using the GNU Compiler Collection
-(GCC)`.
+There are also :switch:`-fstrub={choice}` command-line options to
+control default settings.  For usage and more details on the
+command-line options, on the ``strub`` attribute, and their use with
+other programming languages, see :title:`Using the GNU Compiler
+Collection (GCC)`.
 
 Note that Ada secondary stacks are not scrubbed.  The restriction
 ``No_Secondary_Stack`` avoids their use, and thus their accidental


diff --git a/gcc/ada/gnat_rm.texi b/gcc/ada/gnat_rm.texi
--- a/gcc/ada/gnat_rm.texi
+++ b/gcc/ada/gnat_rm.texi
@@ -21,7 +21,7 @@
 
 @copying
 @quotation
-GNAT Reference Manual , Jun 24, 2022
+GNAT Reference Manual , Jul 11, 2022
 
 AdaCore
 
@@ -28922,9 +28922,10 @@ change.
 GNAT can generate code to zero-out hardware registers before returning
 from a subprogram.
 
-It can be enabled with the @code{-fzero-call-used-regs} command-line
-option, to affect all subprograms in a compilation, and with a
-@code{Machine_Attribute} pragma, to affect only specific subprograms.
+It can be enabled with the @code{-fzero-call-used-regs=@emph{choice}}
+command-line option, to affect all subprograms in a compilation, and
+with a @code{Machine_Attribute} pragma, to affect only specific
+subprograms.
 
 @example
 procedure Foo;
@@ -28975,10 +28976,10 @@ pragma Machine_Attribute (Var, "strub");
 --  scrubbing of the stack space used by that subprogram.
 @end example
 
-There are also @code{-fstrub} command-line options to control
-default settings.  For usage and more details on the command-line
-option, on the @code{strub} attribute, and their use with other
-programming languages, see @cite{Using the GNU Compiler Collection (GCC)}.
+There are also @code{-fstrub=@emph{choice}} command-line options to
+control default settings.  For usage and more details on the
+command-line options, on the @code{strub} attribute, and their use with
+other programming languages, see @cite{Using the GNU Compiler Collection (GCC)}.
 
 Note that Ada secondary stacks are not scrubbed.  The restriction
 @code{No_Secondary_Stack} avoids their use, and thus their accidental