https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119643
Bug ID: 119643
Summary: Subprogram parameter subtypes in
renaming-as-declaration are not ignored
Product: gcc
Version: 14.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: ada
Assignee: unassigned at gcc dot gnu.org
Reporter: mnpjm6zqj6tckbx8zscf at mailbox dot org
CC: dkm at gcc dot gnu.org
Target Milestone: ---
Created attachment 61015
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=61015&action=edit
Source of the test program reproducing the bug
Ada's subprogram "renaming-as-declaration" takes subprogram subtypes from the
profile of the renamed entity.
ARM 2022 [8.5.4] Subprogram Renaming Declarations [1] says:
> Static Semantics
> A renaming-as-declaration declares a new view of the renamed entity.
> The profile of this new view takes its subtypes, parameter modes, and
> calling convention from the original profile of the callable entity,
> while taking the formal parameter names and default_expressions from
> the profile given in the subprogram_renaming_declaration. The new
> view is a function or procedure, never an entry.
This formulation does not forbid changes to the subtypes in a subprogram
renaming-as-declaration.
It warrants, however, that any changed subtypes are not to be considered.
Tests show that in a subprogram renaming declaration a changed return subtype
has no effect (as expected).
On the other hand, changed parameter subtypes seem to be adopted into the new
view of a subprogram (instead of being ignored).
The following program illustrates the erroneous behaviour.
```ada
with Ada.Text_IO;
procedure Rename_Subprogram_Types is
function Incr (V : Integer; I : Integer := 1) return Integer is (V +
I);
function Incr_Ren (V : Integer; I : Positive := 1) return Positive
renames Incr;
-- function Incr_Ren (V : Integer; I : Integer := 1) return Positive
renames Incr;
procedure Test_Incr (V : Integer; I : Integer := 1) is
Blab : constant String := ("Incr_Ren (" & V'Image & ", " & I'Image & ") =
");
begin
Ada.Text_IO.Put (Blab);
Ada.Text_IO.Put (Incr_Ren (V, I)'Image);
Ada.Text_IO.Put (" (subtypes Positive ignored)");
Ada.Text_IO.New_Line;
end Test_Incr;
begin
Test_Incr (-3);
Test_Incr (-3, 2);
Test_Incr (-3, 0);
exception
when Constraint_Error =>
Ada.Text_IO.Put_Line ("Constraint_Error on parameter subtype Positive");
end Rename_Subprogram_Types;
```
Expected output:
```text
Incr_Ren (-3, 1) = -2 (subtypes Positive ignored)
Incr_Ren (-3, 2) = -1 (subtypes Positive ignored)
Incr_Ren (-3, 0) = -3 (subtypes Positive ignored)
```
Actual output:
```console
Incr_Ren (-3, 1) = -2 (subtypes Positive ignored)
Incr_Ren (-3, 2) = -1 (subtypes Positive ignored)
Incr_Ren (-3, 0) = Constraint_Error on parameter subtype Positive
```
Note:
It is enough to swap the comment in the two `Incr_Ren` lines to get the
expected output.
Environment information:
```console
# BUILD COMMAND
#
$ gnatmake -gnatwae rename_subprogram_types.adb
gcc -c -gnatwae rename_subprogram_types.adb
gnatbind -x rename_subprogram_types.ali
gnatlink rename_subprogram_types.ali
# GCC VERSION
#
$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-redhat-linux/14/lto-wrapper
OFFLOAD_TARGET_NAMES=nvptx-none:amdgcn-amdhsa
OFFLOAD_TARGET_DEFAULT=1
Target: x86_64-redhat-linux
Configured with: ../configure --enable-bootstrap
--enable-languages=c,c++,fortran,objc,obj-c++,ada,go,d,m2,lto --prefix=/usr
--mandir=/usr/share/man --infodir=/usr/share/info
--with-bugurl=http://bugzilla.redhat.com/bugzilla --enable-shared
--enable-threads=posix --enable-checking=release --enable-multilib
--with-system-zlib --enable-__cxa_atexit --disable-libunwind-exceptions
--enable-gnu-unique-object --enable-linker-build-id
--with-gcc-major-version-only --enable-libstdcxx-backtrace
--with-libstdcxx-zoneinfo=/usr/share/zoneinfo --with-linker-hash-style=gnu
--enable-plugin --enable-initfini-array
--with-isl=/builddir/build/BUILD/gcc-14.2.1-build/gcc-14.2.1-20250110/obj-x86_64-redhat-linux/isl-install
--enable-offload-targets=nvptx-none,amdgcn-amdhsa --enable-offload-defaulted
--without-cuda-driver --enable-gnu-indirect-function --enable-cet
--with-tune=generic --with-arch_32=i686 --build=x86_64-redhat-linux
--with-build-config=bootstrap-lto --enable-link-serialization=1
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 14.2.1 20250110 (Red Hat 14.2.1-7) (GCC)
# SYSTEM INFORMATION
#
$ uname -mors
Linux 6.13.8-200.fc41.x86_64 x86_64 GNU/Linux
```
[1] www.ada-auth.org/standards/22rm/html/RM-8-5-4.html
