[LLVMdev] -O4 -fvisibility=hidden

[Jack Howarth]

On Mon, Jan 26, 2009 at 09:57:28AM -0800, Devang Patel wrote:
> Hi Jack,
> 
> On Jan 25, 2009, at 10:00 AM, Jack Howarth wrote:
> 
> >    Doing that changes the error messages into a bus
> > error on the darwin linker.
> 
> 
> Pl. file bugzilla report (or radar) with a reproducible test case so  
> that we can investigate this linker crash.
> 
> As you know, one way to control symbol visibility is to use gcc's  
> (inherited by llvm-gcc) visibility support. GCC supports, 1) command  
> line options 2) attributes and 3) pragmas in this regard. Following  
> document provides good summary...
> 
> http://developer.apple.com/documentation/DeveloperTools/Conceptual/CppRuntimeEnv/Articles/SymbolVisibility.html#/ 
> /apple_ref/doc/uid/TP40001670
> 
> Another way to control symbol visibility is to use linker's interface.  
> See ld man page for more info on -exported_symbols_list, - 
> exported_symbols, -unexported_symbols_list etc.. flags. If you're  
> going to try this approach, pl. read ld man page first.
> -
> Devang
> 
> 
> 
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Devang,
   I was surprised to discover that I could build all of
pymol with -fvisibility=hidden using gcc 4.4 or
llvm-gcc-4.2 with only a single header change...

--- pymol-1.1/layer4/Cmd.h.orig 2009-01-30 18:58:58.000000000 -0500
+++ pymol-1.1/layer4/Cmd.h      2009-01-30 19:00:17.000000000 -0500
@@ -18,7 +18,8 @@
 
 #include"os_python.h"
 
-void init_cmd(void);
+void init_cmd(void)
+__attribute__((visibility("default")));
 
 extern PyObject *PM_Globals;
 
One of the advantages of running as a python module I guess. I was
also able to build pymol with -O4 using the llvm 2.5 libLTO.dylib
so that full Link Time Optimizations were performed. Everything
compiled and linked fine. The resulting pymol runs its demos without
regressions. Nice.
             Jack