opt.ads: Elaboration warnings are now on by default.

2017-11-16  Hristian Kirtchev  <kirtchev@adacore.com>

	* opt.ads: Elaboration warnings are now on by default. Add a comment
	explaining why this is needed.
	* sem_ch9.adb (Analyze_Requeue): Preserve the status of elaboration
	warnings.
	* sem_ch12.adb (Analyze_Package_Instantiation): Preserve the status of
	elaboration warnings.
	(Analyze_Subprogram_Instantiation): Preserve the status of elaboration
	warnings.
	* sem_elab.adb: Update the structure of Call_Attributes and
	Instantiation_Attributes.
	(Build_Call_Marker): Propagate the status of elaboration warnings from
	the call to the marker.
	(Extract_Call_Attributes): Extract the status of elaboration warnings.
	(Extract_Instantiation_Attributes): Extract the status of elaboration
	warnings.
	(Process_Conditional_ABE_Activation_Impl): Elaboration diagnostics are
	now dependent on the status of elaboration warnings.
	(Process_Conditional_ABE_Call_Ada): Elaboration diagnostics are now
	dependent on the status of elaboration warnings.
	(Process_Conditional_ABE_Instantiation_Ada): Elaboration diagnostics
	are now dependent on the status of elaboration warnings.
	(Process_Guaranteed_ABE_Activation_Impl): Remove pragma Unreferenced
	for formal Call_Attrs. Elaboration diagnostics are now dependent on the
	status of elaboration warnings.
	(Process_Guaranteed_ABE_Call): Elaboration diagnostics are now
	dependent on the status of elaboration warnings.
	(Process_Guaranteed_ABE_Instantiation): Elaboration diagnostics are now
	dependent on the status of elaboration warnings.
	* sem_prag.adb (Analyze_Pragma): Remove the unjustified warning
	concerning pragma Elaborate.
	* sem_res.adb (Resolve_Call): Preserve the status of elaboration
	warnings.
	(Resolve_Entry_Call): Propagate flag Is_Elaboration_Warnings_OK_Node
	from the procedure call to the entry call.
	* sem_util.adb (Mark_Elaboration_Attributes): Add formal parameter
	Warnings.
	(Mark_Elaboration_Attributes_Node): Preserve the status of elaboration
	warnings
	* sem_util.ads (Mark_Elaboration_Attributes): Add formal parameter
	Warnings. Update the comment on usage.
	* sinfo.adb (Is_Dispatching_Call): Update to use Flag6.
	(Is_Elaboration_Warnings_OK_Node): New routine.
	(Set_Is_Dispatching_Call): Update to use Flag6.
	(Set_Is_Elaboration_Warnings_OK_Node): New routine.
	* sinfo.ads: Attribute Is_Dispatching_Call now uses Flag6. Add new
	attribute Is_Elaboration_Warnings_OK_Node along with occurrences
	in nodes.
	(Is_Elaboration_Warnings_OK_Node): New routine along with pragma
	Inline.
	(Set_Is_Elaboration_Warnings_OK_Node): New routine along with pragma
	Inline.
	* doc/gnat_ugn/elaboration_order_handling_in_gnat.rst: Update various
	sections to indicate how to suppress elaboration warnings.  Document
	switches -gnatwl and -gnatwL.
	* gnat_ugn.texi: Regenerate.

From-SVN: r254819

1 files changed, 52 insertions, 5 deletions

diff --git a/gcc/ada/gnat_ugn.texi b/gcc/ada/gnat_ugn.texi
index 05fdf4c..43ef2459 100644
--- a/gcc/ada/gnat_ugn.texi
+++ b/gcc/ada/gnat_ugn.texi
@@ -21,7 +21,7 @@
 
 @copying
 @quotation
-GNAT User's Guide for Native Platforms , Nov 09, 2017
+GNAT User's Guide for Native Platforms , Nov 16, 2017
 
 AdaCore
 
@@ -27897,8 +27897,8 @@ three models:
 Note that GNAT emits warnings rather than hard errors whenever it encounters an
 elaboration problem. This is because the elaboration model in effect may be too
 conservative, or a particular scenario may not be elaborated or executed due to
-data and control flow. The warnings can be suppressed with compiler switch
-@code{-gnatws}.
+data and control flow. The warnings can be suppressed selectively with @code{pragma
+Warnigns (Off)} or globally with compiler switch @code{-gnatwL}.
 
 @node Dynamic Elaboration Model in GNAT,Static Elaboration Model in GNAT,Common Elaboration-model Traits,Elaboration Order Handling in GNAT
 @anchor{gnat_ugn/elaboration_order_handling_in_gnat dynamic-elaboration-model-in-gnat}@anchor{23e}@anchor{gnat_ugn/elaboration_order_handling_in_gnat id8}@anchor{23f}
@@ -27975,8 +27975,8 @@ run-time checks based on the nature of the target.
 
 The static model performs extensive diagnostics on scenarios which elaborate
 or execute internal targets. The warnings resulting from these diagnostics
-are enabled by default, but can be suppressed using compiler switch
-@code{-gnatws}.
+are enabled by default, but can be suppressed selectively with @code{pragma
+Warnings (Off)} or globally with compiler switch @code{-gnatwL}.
 
 @example
  1. package body Static_Model is
@@ -28959,6 +28959,53 @@ In the example above, the elaboration of declaration @code{Ptr} is assigned
 @code{Func'Access} before the body of @code{Func} has been elaborated.
 @end table
 
+@geindex -gnatwl (gnat)
+
+
+@table @asis
+
+@item @code{-gnatwl}
+
+Turn on warnings for elaboration problems
+
+When this switch is in effect, GNAT emits diagnostics in the form of warnings
+concerning various elaboration problems. The warnings are enabled by default.
+The switch is provided in case all warnings are suppressed, but elaboration
+warnings are still desired.
+
+@item @code{-gnatwL}
+
+Turn off warnings for elaboration problems
+
+When this switch is in effect, GNAT no longer emits any diagnostics in the
+form of warnings. Selective suppression of elaboration problems is possible
+using @code{pragma Warnings (Off)}.
+
+@example
+ 1. package body Selective_Suppression is
+ 2.    function ABE return Integer;
+ 3.
+ 4.    Val_1 : constant Integer := ABE;
+                                   |
+    >>> warning: cannot call "ABE" before body seen
+    >>> warning: Program_Error will be raised at run time
+
+ 5.
+ 6.    pragma Warnings (Off);
+ 7.    Val_2 : constant Integer := ABE;
+ 8.    pragma Warnings (On);
+ 9.
+10.    function ABE return Integer is
+11.    begin
+12.       ...
+13.    end ABE;
+14. end Selective_Suppression;
+@end example
+
+Note that suppressing elaboration warnings does not eliminate run-time
+checks. The example above will still fail at runtime with an ABE.
+@end table
+
 @node Summary of Procedures for Elaboration Control,Inspecting the Chosen Elaboration Order,Elaboration-related Compiler Switches,Elaboration Order Handling in GNAT
 @anchor{gnat_ugn/elaboration_order_handling_in_gnat summary-of-procedures-for-elaboration-control}@anchor{24e}@anchor{gnat_ugn/elaboration_order_handling_in_gnat id16}@anchor{24f}
 @section Summary of Procedures for Elaboration Control