Re: detecting non-PIC in shared lib on Darwin?

[Mike Stump <mrs at apple dot com>]

On Apr 26, 2006, at 6:26 PM, Jack Howarth wrote:
> readelf -d foo.so | grep TEXTREL
>
> Does anyone know if some mechanism like this is possible for Darwin
> shared libraries?

A man page is a terrible thing to waste:

       -segprot name max init (32-bit only)
              Specifies the maximum and initial virtual memory   
protection  of
              the  named segment, name, to be max and  
init ,respectively.  The
              values for max and init are any combination  of  the   
characters
              `r'  (for  read), `w' (for write), `x' (for execute)  
and '-' (no
              access).  The default is `rwx' for the  maximum   
protection  for
              all segments for PowerPC architecures and `rw` for the  
all Intel
              architecures.  The default for the initial   
protection  for  all
              segments  is  `rw'  unless  the segment contains a  
section which
              contains some machine instructions, in which  case   
the  default
              for  the initial protection is `rwx' (and for Intel  
architecures
              it also sets the maximum protection to `rwx' in this  
case).  The
              default for the initial protection for the ``__TEXT''  
segment is
              `rx' (not writable).

so, just add -segprot __TEXT rw rw to the -dynamiclib invocation.

> I ask because we just discovered that the gmp developers
> have been building non-PIC code (due to the usage of -fast without - 
> fPIC)
> in the MacOS X builds. It would be nice to be able to check for the  
> non-PIC
> code in all the shared libs on MacOS X. Thanks in advance for any  
> info.

One cannot usually create a dynamic library with those relocations  
without this flag and will get a failed link.  I'd anticipate that if  
something doesn't so warn, that is a bug.