Re: PIE support (was: 1.5.18: suppressing non-C language checks / pass flags to cc in link mode)

[Paul Jakma]

On Wed, 30 Nov 2005, Mike Frysinger wrote:

> PIE and PIC arent the same thing
>
> -fPIC is for creating position independent code for shared objects
> while -fPIE is for creating position independent code for executables

Right, I did know that ;).

The distinction between the two is mostly important at link-time. Ie 
a collection of PIC and/or PIE objects can be linked together into a 
PIE executable.

What I'm curious about is what the difference is in generated /code/ 
for an object /before/ linking done between PIC and PIE. Is there an 
efficiency/performance gain in generating PIE code over PIC? If so, 
is the gain over PIC sufficiently large to be relevant to Ralf's 
patch (which, if I understand correctly, will compile all code as PIC 
if -fpie is supplied).

If efficiency of PIE targeted code is sufficiently greater than PIC, 
then, AIUI, that would require libtool to distinguish between 
additional modes of compiling objects intended for shared usage (PIC) 
and not (PIE).

Is my understanding anyway.

Alternatively, projects would need to tailor their build systems to 
make the distinction between possibly-intended-to-link-into-shared 
and other ojbects.

regards,
--
Paul Jakma      address@hidden  address@hidden  Key ID: 64A2FF6A
Fortune:
When the speaker and he to whom he is speaks do not understand, that is
metaphysics.
                -- Voltaire