diff options
Diffstat (limited to 'gcc/ada/sem.ads')
| -rw-r--r-- | gcc/ada/sem.ads | 99 |
1 files changed, 72 insertions, 27 deletions
diff --git a/gcc/ada/sem.ads b/gcc/ada/sem.ads index d7fb9a6..6a86aff 100644 --- a/gcc/ada/sem.ads +++ b/gcc/ada/sem.ads @@ -6,7 +6,7 @@ -- -- -- S p e c -- -- -- --- Copyright (C) 1992-2005, Free Software Foundation, Inc. -- +-- Copyright (C) 1992-2006, Free Software Foundation, Inc. -- -- -- -- GNAT is free software; you can redistribute it and/or modify it under -- -- terms of the GNU General Public License as published by the Free Soft- -- @@ -269,12 +269,54 @@ package Sem is -- Scope Stack -- ----------------- - -- The scope stack holds all entries of the scope table. As in the parser, - -- we use Last as the stack pointer, so that we can always find the scope - -- that is currently open in Scope_Stack.Table (Scope_Stack.Last). The - -- oldest entry, at Scope_Stack (0) is Standard. The entries in the table - -- include the entity for the referenced scope, together with information - -- used to restore the proper setting of check suppressions on scope exit. + -- The scope stack indicates the declarative regions that are currently + -- being processed (analyzed and/or expanded). The scope stack is one of + -- basic visibility structures in the compiler: entities that are declared + -- in a scope that is currently on the scope stack are immediately visible. + -- (leaving aside issues of hiding and overloading). + + -- Initially, the scope stack only contains an entry for package Standard. + -- When a compilation unit, subprogram unit, block or declarative region + -- is being processed, the corresponding entity is pushed on the scope + -- stack. It is removed after the processing step is completed. A given + -- entity can be placed several times on the scope stack, for example + -- when processing derived type declarations, freeze nodes, etc. The top + -- of the scope stack is the innermost scope currently being processed. + -- It is obtained through function Current_Scope. After a compilation unit + -- has been processed, the scope stack must contain only Standard. + -- The predicate In_Open_Scopes specifies whether a scope is currently + -- on the scope stack. + + -- This model is complicated by the need to compile units on the fly, in + -- the middle of the compilation of other units. This arises when compiling + -- instantiations, and when compiling run-time packages obtained through + -- rtsfind. Given that the scope stack is a single static and global + -- structure (not originally designed for the recursive processing required + -- by rtsfind for example) additional machinery is needed to indicate what + -- is currently being compiled. As a result, the scope stack holds several + -- contiguous sections that correspond to the compilation of a given + -- compilation unit. These sections are separated by distinct occurrences + -- of package Standard. The currently active section of the scope stack + -- goes from the current scope to the first occurrence of Standard, which + -- is additionally marked with the flag Is_Active_Stack_Base. The basic + -- visibility routine (Find_Direct_Name, sem_ch8) uses this contiguous + -- section of the scope stack to determine whether a given entity is or + -- is not visible at a point. In_Open_Scopes only examines the currently + -- active section of the scope stack. + + -- Similar complications arise when processing child instances. These + -- must be compiled in the context of parent instances, and therefore the + -- parents must be pushed on the stack before compiling the child, and + -- removed afterwards. Routines Save_Scope_Stack and Restore_Scope_Stack + -- are used to set/reset the visibility of entities declared in scopes + -- that are currently on the scope stack, and are used when compiling + -- instance bodies on the fly. + + -- It is clear in retrospect that all semantic processing and visibility + -- structures should have been fully recursive. The rtsfind mechanism, + -- and the complexities brought about by subunits and by generic child + -- units and their instantitions, have led to a hybrid model that carries + -- more state than one would wish. type Scope_Stack_Entry is record Entity : Entity_Id; @@ -294,9 +336,12 @@ package Sem is -- Marks Transient Scopes (See Exp_Ch7 body for details) Previous_Visibility : Boolean; - -- Used when installing the parent (s) of the current compilation - -- unit. The parent may already be visible because of an ongoing - -- compilation, and the proper visibility must be restored on exit. + -- Used when installing the parent(s) of the current compilation unit. + -- The parent may already be visible because of an ongoing compilation, + -- and the proper visibility must be restored on exit. The flag is + -- typically needed when the context of a child unit requires + -- compilation of a sibling. In other cases the flag is set to False. + -- See Sem_Ch10 (Install_Parents, Remove_Parents). Node_To_Be_Wrapped : Node_Id; -- Only used in transient scopes. Records the node which will @@ -306,33 +351,33 @@ package Sem is Actions_To_Be_Wrapped_After : List_Id; -- Actions that have to be inserted at the start or at the end of a -- transient block. Used to temporarily hold these actions until the - -- block is created, at which time the actions are moved to the - -- block. + -- block is created, at which time the actions are moved to the block. Pending_Freeze_Actions : List_Id; - -- Used to collect freeze entity nodes and associated actions that - -- are generated in a inner context but need to be analyzed outside, - -- such as records and initialization procedures. On exit from the - -- scope, this list of actions is inserted before the scope construct - -- and analyzed to generate the corresponding freeze processing and - -- elaboration of other associated actions. + -- Used to collect freeze entity nodes and associated actions that are + -- generated in a inner context but need to be analyzed outside, such as + -- records and initialization procedures. On exit from the scope, this + -- list of actions is inserted before the scope construct and analyzed + -- to generate the corresponding freeze processing and elaboration of + -- other associated actions. First_Use_Clause : Node_Id; - -- Head of list of Use_Clauses in current scope. The list is built - -- when the declarations in the scope are processed. The list is - -- traversed on scope exit to undo the effect of the use clauses. + -- Head of list of Use_Clauses in current scope. The list is built when + -- the declarations in the scope are processed. The list is traversed + -- on scope exit to undo the effect of the use clauses. Component_Alignment_Default : Component_Alignment_Kind; - -- Component alignment to be applied to any record or array types - -- that are declared for which a specific component alignment pragma - -- does not set the alignment. + -- Component alignment to be applied to any record or array types that + -- are declared for which a specific component alignment pragma does not + -- set the alignment. Is_Active_Stack_Base : Boolean; -- Set to true only when entering the scope for Standard_Standard from -- from within procedure Semantics. Indicates the base of the current - -- active set of scopes. Needed by In_Open_Scopes to handle cases - -- where Standard_Standard can be pushed in the middle of the active - -- set of scopes (occurs for instantiations of generic child units). + -- active set of scopes. Needed by In_Open_Scopes to handle cases where + -- Standard_Standard can be pushed anew on the scope stack to start a + -- new active section (see comment above). + end record; package Scope_Stack is new Table.Table ( |