From 5a5925ee30a8f8b43d045726aa7b2a82c6a6af61 Mon Sep 17 00:00:00 2001 From: Ed Schonberg Date: Thu, 24 May 2018 13:06:21 +0000 Subject: [PATCH] [Ada] Infinite loop in the compiler when warning on redundant constructs This patch fixes an infinite loop in the compiler when warnings on redundant constructs are enabled (-gnatwr) and the constructs are use_type clauses that appear (redundantly) in a parent unit and a child unit. The following command: gcc -c -gnatwr root-child.ads must yield: root-child.ads:2:01: warning: "Pack.Typ" is already use-visible through previous use_type_clause at root.ads:2 The following must compile quietly: gcc -c -gnatwr root-child-grand.ads ---- package Pack is type Typ is new Integer; end Pack; ---- with Pack; use type Pack.Typ; package Root is Thing1 : Pack.Typ; end Root; ---- with pack; use type pack.typ; package Root.Child is Thing2 : Pack.Typ := Root.Thing1 * 3; end; ---- with Pack; use type Pack.Typ; package Root.Child.Grand is Thing3 : Pack.Typ := Thing1 + Thing2; end; 2018-05-24 Ed Schonberg gcc/ada/ * sem_ch8.adb (Analyze_Use_Type): Do not assign the Prev_Use_Clause link to a use_type clause if this would cause an infinite loop in the machinery that detects redundant use clauses. This may happen when the redundant clauses appear in the context of a child unit and the context of its parent. From-SVN: r260663 --- gcc/ada/ChangeLog | 8 ++++++++ gcc/ada/sem_ch8.adb | 6 +++++- 2 files changed, 13 insertions(+), 1 deletion(-) diff --git a/gcc/ada/ChangeLog b/gcc/ada/ChangeLog index ae80df8ba77..8f7e51df49d 100644 --- a/gcc/ada/ChangeLog +++ b/gcc/ada/ChangeLog @@ -1,3 +1,11 @@ +2018-05-24 Ed Schonberg + + * sem_ch8.adb (Analyze_Use_Type): Do not assign the Prev_Use_Clause + link to a use_type clause if this would cause an infinite loop in the + machinery that detects redundant use clauses. This may happen when the + redundant clauses appear in the context of a child unit and the context + of its parent. + 2018-05-24 Piotr Trojanek * sinfo.ads: Fix grammar in comment. diff --git a/gcc/ada/sem_ch8.adb b/gcc/ada/sem_ch8.adb index 36172d075c4..8f8b03a3237 100644 --- a/gcc/ada/sem_ch8.adb +++ b/gcc/ada/sem_ch8.adb @@ -3916,10 +3916,14 @@ package body Sem_Ch8 is -- manipulation of the scope stack so we much guard against those cases -- here, otherwise, we must add the new use_type_clause to the previous -- use_type_clause chain in order to mark redundant use_type_clauses as - -- used. + -- used. When the redundant use-type clauses appear in a parent unit and + -- a child unit we must prevent a circularity in the chain that would + -- otherwise result from the separate steps of analysis and installation + -- of the parent context. if Present (Current_Use_Clause (E)) and then Current_Use_Clause (E) /= N + and then Prev_Use_Clause (Current_Use_Clause (E)) /= N and then No (Prev_Use_Clause (N)) then Set_Prev_Use_Clause (N, Current_Use_Clause (E)); -- 2.30.2