Re: Crosspost: Help wanted from comp.compilers

["Robert I. Eachus" <rieachus@attbi.com>]

tmoran@acm.org wrote:
> Are separate compilations using different settings of compiler switches
> considered to be compilations by different compilers/versions, and thus
> not discussed by the ARM but left to compiler writers and users to handle?

I can't answer your question, because I can't see how to give you an 
answer that is both correct and informative.  (Well, I'll answer it: the 
compiler can make daemons fly out of your nose. See, no help.)

Any _implementation_ defines processes for creating an environment, 
adding and deleting units in that environment, and what it means to 
compile a (compilation) unit and put it into the environment.  An 
implementation is allowed to define lots of other things which are not 
part of the "standard mode."

For example with GNAT, to compile in the standard mode you must use 
gnatmake -gnato <compilation unit or pragma>.  The Ada RM says a lot 
about what must happen in standard mode, and allows ANYTHING in 
non-standard mode.  If you use the gcc that is part of GNAT to compile a 
C program?  Shrug, why should the Ada Reference manual care?  As it 
happens the compiler depends on a .ads or .adb source file extension to 
indicate a compile in standard Ada mode, and other source file 
extensions to indicate other languages.

Similarly, the RM says a lot about what must happen with standard 
pragmas, and attribute specification clauses.  The implementation can 
define compile time flags to have a similar effect, but it can't change 
the meaning of a _language_ defined attribute or pragma.

Now to answer the question that I think you had.  What is said in clause 
10 is absolute. A compiler can keep two sets of compilation units in the 
library, one compiled with debugger support and one without, and use a 
link or run-time option to determine which version you get.  Not a 
problem.  But the units have to be compiled into the environment in 
10.1.4 order and a consistant and legal set chosen at run-time in 
accordance with 10.2--if you are in standard Ada mode.  (And as should 
be clear NONE of this applies to C or Fortran mode, or whatever.)

-- 

                                             Robert I. Eachus

�In an ally, considerations of house, clan, planet, race are 
insignificant beside two prime questions, which are: 1. Can he shoot? 2. 
Will he aim at your enemy?� -- from the Laiden novels by Sharon Lee and 
Steve Miller.