Re: Ada.Execution_Time

[anon@att.net]

In <op.vno2nwchlzeukk@jellix.jlfencey.com>, "Vinzent Hoefler" <0439279208b62c95f1880bf0f8776eeb@t-domaingrabbing.de> writes:
>Randy Brukardt wrote:
>
>
>I believe, back in the old days, there was a requirement that the presence or
>absence of a pragma shall have no effect on the legality of the program, wasn't
>it?

Actually, it still does: Ada 83 thriough 2012 states in Chapter 2 

2.8 Pragmas

In Ada 83 it states:

    A pragma that is not language-defined has no effect if  its  identifier  is
    not  recognized  by  the  (current)  implementation.  Furthermore, a pragma
    (whether language-defined or implementation-defined) has no effect  if  its
    placement  or  its  arguments  do not correspond to what is allowed for the
    pragma.  The region of text over which a pragma has an  effect  depends  on
    the pragma. 

    Note: 

    It  is  recommended  (but not required) that implementations issue warnings
    for pragmas that are not recognized and therefore ignored. 


In Ada 95 .. 2012 states:


                         Implementation Requirements

13    The implementation shall give a warning message for an unrecognized
pragma name.

                         Implementation Permissions

15    An implementation may ignore an unrecognized pragma even if it violates
some of the Syntax Rules, if detecting the syntax error is too complex.

                            Implementation Advice

16    Normally, implementation-defined pragmas should have no semantic effect
for error-free programs; that is, if the implementation-defined pragmas are
removed from a working program, the program should still be legal, and should
still have the same semantics.




In Ada 83 the unrecognized pragmas was syntactically check and skipped
with an optional  simple warning that the compiler will skip that pragma.  
But in Ada 94 .. 2012 it is a question to what the Implementation will do.
It kinds of kills the Ada concept of "predictable" and that's a shame for all 
who controls the design of Ada.