https://gcc.gnu.org/g:4ff0bd5f98728d14a91d62d44fe1fa4bdd0bee33
commit r16-4993-g4ff0bd5f98728d14a91d62d44fe1fa4bdd0bee33 Author: Gary Dismukes <[email protected]> Date: Thu Oct 16 21:38:38 2025 +0000 ada: Crash on call to a dispatching op with if_expr and tag-indeterminate calls The compiler can crash with a Storage_Error for a failed precondition when compiling a call to a dispatching subprogram where an actual for a controlling formal is given by an if_expression whose dependent expressions are tag-indeterminate calls. This problem showed up on a build of Alire (on the compilation of alire-roots.adb) done during a build_gnat_world mailserver (as well as having been noticed and reported separately by another engineering team). The code in Sem_Disp.Check_Dispatching_Call for checking nondispatching procedure calls for actuals that are calls to abstract tag-indeterminate functions did not account for conditional expressions, and attempted to retrieve the (nonexistent) Expression field from an N_If_Expression node, failing the precondition for Expression. It was discovered that none of the code checking for illegal calls to abstract tag-indeterminate functions in procedure calls is needed, and the whole related "elsif" part is removed by this change. (Note that there is separate checking done separately within Check_Dispatching_Call that will catch nondispatching calls to abstract functions.) gcc/ada/ChangeLog: * sem_disp.adb (Check_Dispatching_Call): Remove "elsif" that does error checking for abstract tag-indeterminate calls (seems to be no longer needed). Diff: --- gcc/ada/sem_disp.adb | 50 -------------------------------------------------- 1 file changed, 50 deletions(-) diff --git a/gcc/ada/sem_disp.adb b/gcc/ada/sem_disp.adb index 5a8bd58b8b81..4a940e7f30bd 100644 --- a/gcc/ada/sem_disp.adb +++ b/gcc/ada/sem_disp.adb @@ -586,7 +586,6 @@ package body Sem_Disp is Actual : Node_Id; Formal : Entity_Id; Control : Node_Id := Empty; - Func : Entity_Id; Subp_Entity : constant Entity_Id := Entity (Name (N)); Indeterm_Ctrl_Type : Entity_Id := Empty; @@ -1099,55 +1098,6 @@ package body Sem_Disp is Check_Dispatching_Context (N); - elsif Nkind (N) /= N_Function_Call then - - -- The call is not dispatching, so check that there aren't any - -- tag-indeterminate abstract calls left among its actuals. - - Actual := First_Actual (N); - while Present (Actual) loop - if Is_Tag_Indeterminate (Actual) then - - -- Function call case - - if Nkind (Original_Node (Actual)) = N_Function_Call then - Func := Entity (Name (Original_Node (Actual))); - - -- If the actual is an attribute then it can't be abstract - -- (the only current case of a tag-indeterminate attribute - -- is the stream Input attribute). - - elsif Nkind (Original_Node (Actual)) = N_Attribute_Reference - then - Func := Empty; - - -- Ditto if it is an explicit dereference - - elsif Nkind (Original_Node (Actual)) = N_Explicit_Dereference - then - Func := Empty; - - -- Only other possibility is a qualified expression whose - -- constituent expression is itself a call. - - else - Func := - Entity (Name (Original_Node - (Expression (Original_Node (Actual))))); - end if; - - if Present (Func) and then Is_Abstract_Subprogram (Func) then - Error_Msg_N - ("call to abstract function must be dispatching", - Actual); - end if; - end if; - - Next_Actual (Actual); - end loop; - - Check_Dispatching_Context (N); - elsif Nkind (Parent (N)) in N_Subexpr then Check_Dispatching_Context (N);
