Multiple _OBJC_Module in the same shared library/framework, not so good

[Nat!]

Hi

there is a problem I ran into with static NSStrings in frameworks +load 
methods, which I wanted to share. 

If I read the gnu runtime correctly, then for every struct objc_module 
(_OBJC_Module), there is eventually a call to __objc_exec_class.

__objc_exec_class does in succession a couple of initialization steps 

o) on the first run, one big time objc init

o) add classes/prototypes
o) hack static strings 
o) call +load

I suppose there is one _OBJC_Module per compile unit (i.e. file), but even if 
not, irregardless, currently multiple _OBJC_Module can appear in a .so file and 
then this otherwise harmless looking code will crash:

a.m:    
#import <Foundation/Foundation.h>

NSString  *A = @"A";


@implementation ATest

+ (void) load
{
  extern NSString  *Z;

  printf( "+[ATest load]\n");
  printf( "Z=%s\n", [Z cString]);
}

@end


z.m:
#import <Foundation/Foundation.h>

NSString  *Z = @"Z";


@implementation ZTest

+ (void) load
{
  extern NSString  *A;

  printf( "+[ZTest load]\n");   
  printf( "%s\n", [A cString]);
}

@end


It will crash, because one of the +load is happening before the external 
NXConstantString is fixed up.

This is not optimal. Optimally, the linker should combine multiple 
_OBJC_Modules into one for each shared library.

The workaround is to not use static NSStrings that are defined outside the 
current file in the same framework/library/tool during +load. static NSStrings 
in dependent linkage should be fine. (e.g. gui linking with base or so)

Ciao
  Nat!
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