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| author | Eric Botcazou <ebotcazou@adacore.com> | 2024-05-19 15:45:34 +0200 |
|---|---|---|
| committer | Marc Poulhiès <poulhies@adacore.com> | 2024-06-20 10:50:54 +0200 |
| commit | ce59982c28e19b2c478e12e4afc7b03e8793498b (patch) | |
| tree | ff5d8bd71fa4c64f5b5799d59c9de1184b6c8467 /gcc/ada | |
| parent | 664e47e64cdb8b12dbf7051b9bda9fbac54fb27a (diff) | |
| download | gcc-ce59982c28e19b2c478e12e4afc7b03e8793498b.zip gcc-ce59982c28e19b2c478e12e4afc7b03e8793498b.tar.gz gcc-ce59982c28e19b2c478e12e4afc7b03e8793498b.tar.bz2 | |
ada: Enforce strict alignment for array types with aliased component
This was initially implemented as part of AI12-001 but immediately disabled
because it breaks Florist on 32-bit platforms. However, it is possible to
reenable it in almost all cases without affecting Florist, and the -gnatd_l
switch can now be used to disable it again.
gcc/ada/
* debug.adb (d_l): Document new usage for the compiler.
* freeze.adb (Check_Strict_Alignment): Set the Strict_Alignment
flag on array types with aliased component, except if the
component size is equal to the storage unit or the -gnatd_l switch
is specified.
Diffstat (limited to 'gcc/ada')
| -rw-r--r-- | gcc/ada/debug.adb | 5 | ||||
| -rw-r--r-- | gcc/ada/freeze.adb | 30 |
2 files changed, 22 insertions, 13 deletions
diff --git a/gcc/ada/debug.adb b/gcc/ada/debug.adb index 97f88b7..f7fcd39 100644 --- a/gcc/ada/debug.adb +++ b/gcc/ada/debug.adb @@ -148,7 +148,7 @@ package body Debug is -- d_i Ignore activations and calls to instances for elaboration -- d_j Read JSON files and populate Repinfo tables (opposite of -gnatRjs) -- d_k In CodePeer mode disable expansion of assertion checks - -- d_l + -- d_l Disable strict alignment of array types with aliased component -- d_m -- d_n -- d_o @@ -989,6 +989,9 @@ package body Debug is -- enabled, expansion of assertion expressions is controlled by -- pragma Assertion_Policy. + -- d_l The compiler does not enforce the strict alignment of array types + -- that are declared with an aliased component. + -- d_p The compiler ignores calls to subprograms which verify the run-time -- semantics of invariants and postconditions in both the static and -- dynamic elaboration models. diff --git a/gcc/ada/freeze.adb b/gcc/ada/freeze.adb index d0dd1de..3c3d038 100644 --- a/gcc/ada/freeze.adb +++ b/gcc/ada/freeze.adb @@ -2374,18 +2374,24 @@ package body Freeze is elsif Is_Array_Type (E) then Set_Strict_Alignment (E, Strict_Alignment (Component_Type (E))); - -- ??? AI12-001: Any component of a packed type that contains an - -- aliased part must be aligned according to the alignment of its - -- subtype (RM 13.2(7)). This means that the following test: - - -- if Has_Aliased_Components (E) then - -- Set_Strict_Alignment (E); - -- end if; - - -- should be implemented here. Unfortunately it would break Florist, - -- which has the bad habit of overaligning all the types it declares - -- on 32-bit platforms. Other legacy codebases could also be affected - -- because this check has historically been missing in GNAT. + -- RM 13.2(7.1/4): Any component of a packed type that contains an + -- aliased part shall be aligned according to the alignment of its + -- subtype. + + -- Unfortunately this breaks Florist, which has had the bad habit + -- of overaligning all the types it declares on 32-bit platforms, + -- so make an exception if the component size is the storage unit. + + -- Other legacy codebases could also be affected because this was + -- historically not enforced, so -gnatd_l can be used to disable it. + + if Has_Aliased_Components (E) + and then not (Known_Component_Size (E) + and then Component_Size (E) = System_Storage_Unit) + and then not Debug_Flag_Underscore_L + then + Set_Strict_Alignment (E); + end if; elsif Is_Record_Type (E) then Comp := First_Component (E); |