https://gcc.gnu.org/g:fd7b43f5f4a3a9d3f928cd113730208484dc2889
commit r16-5000-gfd7b43f5f4a3a9d3f928cd113730208484dc2889 Author: Eric Botcazou <[email protected]> Date: Tue Oct 21 23:33:01 2025 +0200 ada: Restore alignment check for address clause given with alignment clause The alignment check for address clauses had historically been performed universally by GNAT, until a decade ago when it was disabled by default on non-strict-alignment platforms. This seems questionable when an alignment clause is also given for the entity since the intent is clear, so the change restores it as well as its associated warning. Moreover, this alignment check had historically been subsumed into the language-defined Range_Check, until two decades ago when it became the implementation-defined Alignment_Check, while still being part of the Range_Check to ease the transition. Now is probably a good time to cut the apron strings and make Alignment_Check standalone. gcc/ada/ChangeLog: * doc/gnat_rm/representation_clauses_and_pragmas.rst (Address Clauses): Adjust description of alignment checks. * sem_ch13.adb (Address_Clause_Check_Record): Remove now unused Alignment_Checks_Suppressed component. (Alignment_Checks_Suppressed): Delete. (Analyze_Attribute_Definition_Clause) <Attribute_Alignment>: Do not consider the status of range checks to decide whether to generate an alignment check. Always generate it if an alignment clause is also given for the entity. <Attribute_Alignment>: Generate an alignment check if an address clause is also given for the entity. (Register_Address_Clause_Check): Adjust for above removal. (Validate_Address_Clauses): Test the Check_Address_Alignment flag on the clause to decide whether to give the warning. * gnat_rm.texi: Regenerate. * gnat_ugn.texi: Regenerate. Diff: --- .../gnat_rm/representation_clauses_and_pragmas.rst | 3 +- gcc/ada/gnat_rm.texi | 5 +-- gcc/ada/gnat_ugn.texi | 4 +- gcc/ada/sem_ch13.adb | 50 ++++++++-------------- 4 files changed, 23 insertions(+), 39 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 7250f6586ee1..65bb1877f7c6 100644 --- a/gcc/ada/doc/gnat_rm/representation_clauses_and_pragmas.rst +++ b/gcc/ada/doc/gnat_rm/representation_clauses_and_pragmas.rst @@ -1580,8 +1580,7 @@ machines with strict alignment requirements, GNAT checks (at compile time if possible, generating a warning, or at execution time with a run-time check) that the alignment is appropriate. If the run-time check fails, then ``Program_Error`` is raised. This run-time -check is suppressed if range checks are suppressed, or if the special GNAT -check Alignment_Check is suppressed, or if +check is suppressed if the GNAT 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). diff --git a/gcc/ada/gnat_rm.texi b/gcc/ada/gnat_rm.texi index 68a3c143dd13..23c9977ed4c3 100644 --- a/gcc/ada/gnat_rm.texi +++ b/gcc/ada/gnat_rm.texi @@ -19,7 +19,7 @@ @copying @quotation -GNAT Reference Manual , Oct 17, 2025 +GNAT Reference Manual , Oct 31, 2025 AdaCore @@ -20724,8 +20724,7 @@ machines with strict alignment requirements, GNAT checks (at compile time if possible, generating a warning, or at execution time with a run-time check) that the alignment is appropriate. If the run-time check fails, then @code{Program_Error} is raised. This run-time -check is suppressed if range checks are suppressed, or if the special GNAT -check Alignment_Check is suppressed, or if +check is suppressed if the GNAT 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). diff --git a/gcc/ada/gnat_ugn.texi b/gcc/ada/gnat_ugn.texi index 86b2cbc5d3f7..478975739f12 100644 --- a/gcc/ada/gnat_ugn.texi +++ b/gcc/ada/gnat_ugn.texi @@ -19,7 +19,7 @@ @copying @quotation -GNAT User's Guide for Native Platforms , Oct 06, 2025 +GNAT User's Guide for Native Platforms , Oct 31, 2025 AdaCore @@ -30333,8 +30333,8 @@ to permit their use in free software. @printindex ge -@anchor{gnat_ugn/gnat_utility_programs switches-related-to-project-files}@w{ } @anchor{d2}@w{ } +@anchor{gnat_ugn/gnat_utility_programs switches-related-to-project-files}@w{ } @c %**end of body @bye diff --git a/gcc/ada/sem_ch13.adb b/gcc/ada/sem_ch13.adb index 131df3d65d6d..31af1bb4675c 100644 --- a/gcc/ada/sem_ch13.adb +++ b/gcc/ada/sem_ch13.adb @@ -442,11 +442,6 @@ package body Sem_Ch13 is Off : Boolean; -- Whether the address is offset within Y in the second case - - Alignment_Checks_Suppressed : Boolean; - -- Whether alignment checks are suppressed by an active scope suppress - -- setting. We need to save the value in order to be able to reuse it - -- after the back end has been run. end record; package Address_Clause_Checks is new Table.Table ( @@ -457,26 +452,6 @@ package body Sem_Ch13 is Table_Increment => 200, Table_Name => "Address_Clause_Checks"); - function Alignment_Checks_Suppressed - (ACCR : Address_Clause_Check_Record) return Boolean; - -- Return whether the alignment check generated for the address clause - -- is suppressed. - - --------------------------------- - -- Alignment_Checks_Suppressed -- - --------------------------------- - - function Alignment_Checks_Suppressed - (ACCR : Address_Clause_Check_Record) return Boolean - is - begin - if Checks_May_Be_Suppressed (ACCR.X) then - return Is_Check_Suppressed (ACCR.X, Alignment_Check); - else - return ACCR.Alignment_Checks_Suppressed; - end if; - end Alignment_Checks_Suppressed; - ----------------------------------------- -- Adjust_Record_For_Reverse_Bit_Order -- ----------------------------------------- @@ -7086,11 +7061,15 @@ package body Sem_Ch13 is end if; end; - -- Entity has delayed freeze, so we will generate an + -- The entity has delayed freeze, so we will generate an -- alignment check at the freeze point unless suppressed. + -- We will unconditionally generate it when the alignment + -- is specified in addition to the address, to compensate + -- for the check being suppressed by default on machines + -- that do not need strict alignment of memory accesses. - if not Range_Checks_Suppressed (U_Ent) - and then not Alignment_Checks_Suppressed (U_Ent) + if not Alignment_Checks_Suppressed (U_Ent) + or else Present (Alignment_Clause (U_Ent)) then Set_Check_Address_Alignment (N); end if; @@ -7165,6 +7144,14 @@ package body Sem_Ch13 is if Is_Array_Type (U_Ent) then Set_Alignment (Base_Type (U_Ent), Align); end if; + + -- See the Attribute_Address case above for the rationale + + if not Is_Type (U_Ent) + and then Present (Address_Clause (U_Ent)) + then + Set_Check_Address_Alignment (Address_Clause (U_Ent)); + end if; end if; end Alignment; @@ -16669,9 +16656,8 @@ package body Sem_Ch13 is Y : Entity_Id; Off : Boolean) is - ACS : constant Boolean := Scope_Suppress.Suppress (Alignment_Check); begin - Address_Clause_Checks.Append ((N, X, A, Y, Off, ACS)); + Address_Clause_Checks.Append ((N, X, A, Y, Off)); end Register_Address_Clause_Check; ------------------------ @@ -19121,7 +19107,7 @@ package body Sem_Ch13 is -- Check for known value not multiple of alignment if No (ACCR.Y) then - if not Alignment_Checks_Suppressed (ACCR) + if Check_Address_Alignment (ACCR.N) and then X_Alignment /= 0 and then ACCR.A mod X_Alignment /= 0 then @@ -19166,7 +19152,7 @@ package body Sem_Ch13 is -- Note: we do not check the alignment if we gave a size -- warning, since it would likely be redundant. - elsif not Alignment_Checks_Suppressed (ACCR) + elsif Check_Address_Alignment (ACCR.N) and then Y_Alignment /= Uint_0 and then (Y_Alignment < X_Alignment
