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* [gcc r12-6317] [Ada] Warn on subtype declaration of null range
@ 2022-01-06 17:15 Pierre-Marie de Rodat
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From: Pierre-Marie de Rodat @ 2022-01-06 17:15 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:2a60c08e98acaae212840b2d3329b5bd13778581
commit r12-6317-g2a60c08e98acaae212840b2d3329b5bd13778581
Author: Bob Duff <duff@adacore.com>
Date: Fri Dec 10 06:01:22 2021 -0500
[Ada] Warn on subtype declaration of null range
gcc/ada/
* sem_res.adb (Resolve_Range): Warn on null range, unless we are
inside a generic unit or an instance thereof.
* sem_ch3.adb (Analyze_Subtype_Indication): Minor: avoid double
negative.
Diff:
---
gcc/ada/sem_ch3.adb | 8 ++++----
gcc/ada/sem_res.adb | 24 ++++++++++++++++++++++++
2 files changed, 28 insertions(+), 4 deletions(-)
diff --git a/gcc/ada/sem_ch3.adb b/gcc/ada/sem_ch3.adb
index 7643cd16377..ce5f4536a26 100644
--- a/gcc/ada/sem_ch3.adb
+++ b/gcc/ada/sem_ch3.adb
@@ -6048,13 +6048,13 @@ package body Sem_Ch3 is
begin
Analyze (T);
- if R /= Error then
+ if R = Error then
+ Set_Error_Posted (R);
+ Set_Error_Posted (T);
+ else
Analyze (R);
Set_Etype (N, Etype (R));
Resolve (R, Entity (T));
- else
- Set_Error_Posted (R);
- Set_Error_Posted (T);
end if;
end Analyze_Subtype_Indication;
diff --git a/gcc/ada/sem_res.adb b/gcc/ada/sem_res.adb
index 9a635068915..44b041431c8 100644
--- a/gcc/ada/sem_res.adb
+++ b/gcc/ada/sem_res.adb
@@ -10754,6 +10754,30 @@ package body Sem_Res is
Fold_Uint (H, Expr_Value (H), Static => True);
end if;
end if;
+
+ -- If we have a compile-time-known null range, we warn, because that is
+ -- likely to be a mistake. (Dynamic null ranges make sense, but often
+ -- compile-time-known ones do not.) Warn only if this is in a subtype
+ -- declaration. We do this here, rather than while analyzing a subtype
+ -- declaration, in case we decide to expand the cases. We do not want to
+ -- warn in all cases, because some are idiomatic, such as an empty
+ -- aggregate (1 .. 0 => <>).
+
+ -- We don't warn in generics or their instances, because there might be
+ -- some instances where the range is null, and some where it is not,
+ -- which would lead to false alarms.
+
+ if not (Inside_A_Generic or In_Instance)
+ and then Comes_From_Source (N)
+ and then Compile_Time_Compare
+ (Low_Bound (N), High_Bound (N), Assume_Valid => True) = GT
+ and then Nkind (Parent (N)) = N_Range_Constraint
+ and then Nkind (Parent (Parent (N))) = N_Subtype_Indication
+ and then Nkind (Parent (Parent (Parent (N)))) = N_Subtype_Declaration
+ and then Is_OK_Static_Range (N)
+ then
+ Error_Msg_N ("null range??", N);
+ end if;
end Resolve_Range;
--------------------------
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