diff options
| -rw-r--r-- | gcc/ada/doc/gnat_rm/representation_clauses_and_pragmas.rst | 17 | ||||
| -rw-r--r-- | gcc/ada/gnat_rm.texi | 17 | ||||
| -rw-r--r-- | gcc/ada/sem_ch13.adb | 51 |
3 files changed, 66 insertions, 19 deletions
diff --git a/gcc/ada/doc/gnat_rm/representation_clauses_and_pragmas.rst b/gcc/ada/doc/gnat_rm/representation_clauses_and_pragmas.rst index f755fc1..3bb579b 100644 --- a/gcc/ada/doc/gnat_rm/representation_clauses_and_pragmas.rst +++ b/gcc/ada/doc/gnat_rm/representation_clauses_and_pragmas.rst @@ -1585,9 +1585,20 @@ check Alignment_Check is suppressed, or if ``pragma Restrictions (No_Elaboration_Code)`` is in effect. It is also suppressed by default on non-strict alignment machines (such as the x86). -Finally, GNAT does not permit overlaying of objects of class-wide types. In -most cases, the compiler can detect an attempt at such overlays and will -generate a warning at compile time and a Program_Error exception at run time. +In some cases, GNAT does not support an address specification (using either +form of aspect specification syntax) for the declaration of an object that has +an indefinite nominal subtype. An object declaration has an indefinite +nominal subtype if it takes its bounds (for an array type), discriminant +values (for a discriminated type whose discriminants lack defaults), or tag +(for a class-wide type) from its initial value, as in + +.. code-block:: ada + + X : String := Some_Function_Call; + -- String has no constraint, so bounds for X come from function call + +This restriction does not apply if the size of the object's initial value is +known at compile time and the type of the object is not class-wide. .. index:: Export diff --git a/gcc/ada/gnat_rm.texi b/gcc/ada/gnat_rm.texi index 814b4d3..388528b 100644 --- a/gcc/ada/gnat_rm.texi +++ b/gcc/ada/gnat_rm.texi @@ -20176,9 +20176,20 @@ check Alignment_Check is suppressed, or if @code{pragma Restrictions (No_Elaboration_Code)} is in effect. It is also suppressed by default on non-strict alignment machines (such as the x86). -Finally, GNAT does not permit overlaying of objects of class-wide types. In -most cases, the compiler can detect an attempt at such overlays and will -generate a warning at compile time and a Program_Error exception at run time. +In some cases, GNAT does not support an address specification (using either +form of aspect specification syntax) for the declaration of an object that has +an indefinite nominal subtype. An object declaration has an indefinite +nominal subtype if it takes its bounds (for an array type), discriminant +values (for a discriminated type whose discriminants lack defaults), or tag +(for a class-wide type) from its initial value, as in + +@example +X : String := Some_Function_Call; +-- String has no constraint, so bounds for X come from function call +@end example + +This restriction does not apply if the size of the object’s initial value is +known at compile time and the type of the object is not class-wide. @geindex Export diff --git a/gcc/ada/sem_ch13.adb b/gcc/ada/sem_ch13.adb index cf19438..3cac123 100644 --- a/gcc/ada/sem_ch13.adb +++ b/gcc/ada/sem_ch13.adb @@ -6550,22 +6550,47 @@ package body Sem_Ch13 is ("\?j?use interrupt procedure instead", N); end if; - -- Case of an address clause for a class-wide object, which is - -- considered erroneous. - - elsif Is_Class_Wide_Type (Etype (U_Ent)) then - Error_Msg_NE - ("??class-wide object & must not be overlaid", Nam, U_Ent); - Error_Msg_N - ("\??Program_Error will be raised at run time", Nam); - Insert_Action (Declaration_Node (U_Ent), - Make_Raise_Program_Error (Loc, - Reason => PE_Overlaid_Controlled_Object)); - return; - -- Case of address clause for an object elsif Ekind (U_Ent) in E_Constant | E_Variable then + + -- Disallow case of an address clause for an object of an + -- indefinite subtype which takes its bounds/discriminant/tag + -- from its initial value. Without this, we get a Gigi + -- assertion failure for things like + -- X : String := Some_Function (...) with Address => ...; + -- where the result subtype of the function is unconstrained. + -- + -- We want to reject two cases: the class-wide case, and the + -- case where the FE conjures up a renaming declaration and + -- would then otherwise generate an address specification for + -- that renaming (which is a malformed tree, which is why Gigi + -- complains). + + if Is_Class_Wide_Type (Etype (U_Ent)) then + Error_Msg_N + ("address specification not supported for class-wide " & + "object declaration", Nam); + return; + elsif Is_Constr_Subt_For_U_Nominal (Etype (U_Ent)) + and then + Nkind (Parent (U_Ent)) = N_Object_Renaming_Declaration + then + -- Confirm accuracy of " and dynamic size" message text + -- before including it. We want to include that text when + -- it is correct because it may be useful to the reader. + -- The case where we omit that part of the message text + -- might be dead code, but let's not rely on that. + + Error_Msg_N + ("address specification not supported for object " & + "declaration with indefinite nominal subtype" & + (if Size_Known_At_Compile_Time (Etype (U_Ent)) + then "" + else " and dynamic size"), Nam); + return; + end if; + declare Expr : constant Node_Id := Expression (N); O_Ent : Entity_Id; |