[FFmpeg-devel] Why 'You can only build one library type at once on MinGW'?

Måns Rullgård mans
Wed May 9 16:57:01 CEST 2007

Rich Felker wrote:
> On Wed, May 09, 2007 at 10:50:56AM +0200, Michel Bardiaux wrote:
>> >> while under Linux they're different (shared objects
>> >> needs to be compiled with -fPIC and access global data through %ebx?),
>> No, PIC is usually not required. PIC just guarantees the dso can be
>> relocated to any address. Without that its not possible to run when
>> there are conflicts of address ranges.
> Nope, this is not true. Rather, without PIC, relocations remain inline
> in the code rather than isolated to GOT/PLT tables. This means that
> the dynamic linker must modify large amounts of code at startup
> (runtime), resulting in unsharable pages and bad initial performance.
> However it in no way precludes relocation.

On x86_64 it does, at least in the general case.  A 32-bit immediate operand
might need 64 bits after relocation.  Theoretically, the compiler could have
a flag telling it to make all relocatable values 64-bit, but gcc doesn't to
my knowledge have such an option.

M?ns Rullg?rd
mans at mansr.com

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