Re: CFLAGS/LDFLAGS for PIE vs PIC?

[Bryan Ischo]

On 04/01/12 23:10, John Calcote wrote:

> Perhaps I'm showing my ignorance here, but I find it difficult to understand
> why any source file should ever be compiled without -fPIC. Are we really
> worried about a few bytes of storage or memory in this day and age? This
> flag has been the crux of all logistical problems I've ever dealt with when
> building linux objects.
>
> For example, there are times when I need to build objects that will be
> linked statically into a program AND statically into a shared library. Do I
> build two static libraries: one called libutil_static.a and libutil.a? That
> seems silly and wasteful. Rather, I've found it simpler in this case to just
> build all these "util" source files with -fPIC and archive them all into one
> libutil.a that can be linked both into my programs and into my shared
> libraries.
>
> If anyone has any input, I'd love to hear good reasons for not just
> disregarding non-pic code these days.

Always building objects with PIC flags is a fine choice too if that's 
the way you want to go.  I have experienced embedded environments where 
the difference in code size and performance of unnecessary PIC code was 
an issue, but that is a very specific scenario and not relevant to 99.9% 
of the cases where these choices are made.

I personally just like to solve problems in a way that feels the "most 
correct".  Somehow letting little things slide gives me a sense that an 
inevitable creep towards poor quality will result.  It's why I always 
build correct functional dependency rules in my makefiles, why I don't 
ever use recursive make, and why I care about compiler warnings that 
wouldn't otherwise stop the compilation unless I pass a -Werr flag 
(which I always do).  It gives me a sense of completeness to know that 
only the code that needs to be PIC in my program or libraries is PIC.

But as far as I know, this factor aside, and excepting also those very 
rare cases where the size or performance penalties of PIC matter, there 
is no reason otherwise to not always compile everything PIC, in which 
case making a Makefile, either manually written or generated using GNU 
autoconf, is an easier task.

Bryan