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Date: Tue, 18 Jan 2022 03:05:53 -0800 (PST)
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Subject: Odd Behaviour
From: Mark Wilson <markwilson@wilsonnet.technology>
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Xref: reader02.eternal-september.org comp.lang.ada:63381
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If I use,

   procedure SQLAllocHandle
     (Result          : out    SQLRETURN;
      HandleType      : in     SQL_HANDLE_TYPE;
      InputHandle     : in     SQLHANDLE;
      OutputHandlePtr : in out SQLHANDLE)
     with
       Import        => True,
       Convention    => C,
       External_Name => "SQLAllocHandle";
   pragma Import_Valued_Procedure (SQLAllocHandle);

then everything works as expected. However, if I add the following Pre and Post conditions (it's definitely not the Global or Depends)

   procedure SQLAllocHandle
     (Result          : out    SQLRETURN;
      HandleType      : in     SQL_HANDLE_TYPE;
      InputHandle     : in     SQLHANDLE;
      OutputHandlePtr : in out SQLHANDLE)
     with
       Import        => True,
       Convention    => C,
       External_Name => "SQLAllocHandle",
       Global        => null,
       Depends       => ((Result, OutputHandlePtr) =>
                           (HandleType, InputHandle, OutputHandlePtr)),
       Pre           => (if HandleType = SQL_HANDLE_ENV then
                            InputHandle = SQL_NULL_HANDLE
                         else
                            InputHandle /= SQL_NULL_HANDLE),
       Post          => (if SQL_OK (Result) then
                            OutputHandlePtr /= SQL_NULL_HANDLE
                         else
                            OutputHandlePtr = SQL_NULL_HANDLE);

   pragma Import_Valued_Procedure (SQLAllocHandle);

then an error is raised: 'warning: Valued_Procedure has no effect for convention Ada [enabled by default]' If I ignore the error, using

 pragma Warnings (Off, "*convention Ada*");

 then it doesn't work at all, as one would expect, raising storage_error.

So, is it the case that, even if you suppress all checks, using an 'if' in a pre or post condition forces a import function stub to only be convention Ada?