steved@teklds.TEK.COM (Steve Dum) (08/09/88)
When the loader is trying to resolve a undefined symbol, (nm says type 'U')
if it finds a module which has the symbol declared as uninitialized data
(nm says type 'C') in a library the loader extracts the size of the variable
from that module, but it does not load in the module. Does anyone know if
this 'feature' is required by anything, or just due to historical reasons.
It looks like a bug to me.
This is on a 4.3 system, but I don't think it is 4.3 specific.
The reason I ask, is that this is exactly the wrong action for what I
want to do. Namely, a c++ compiler can define data as uninitialized
and also defines an initialiation routine which is resolved at load time
by doing a partial load and then building a table of initialization
routines to be called at program execution. By only using the size,
and not loading the rest of the module the variable is defined in,
the code generated is incorrect.
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Stephen Dum (503)-629-1146
US Mail: Tektronix, Inc., MS 92-800, P.O. Box 4600, Beaverton, OR 97076-4600
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CS,ARPAnet: steved@teklds.TEK.COMleo@philmds.UUCP (Leo de Wit) (08/12/88)
In article <3787@teklds.TEK.COM> steved@teklds.TEK.COM (Steve Dum) writes: > >When the loader is trying to resolve a undefined symbol, (nm says type 'U') >if it finds a module which has the symbol declared as uninitialized data >(nm says type 'C') in a library the loader extracts the size of the variable >from that module, but it does not load in the module. Does anyone know if >this 'feature' is required by anything, or just due to historical reasons. >It looks like a bug to me. Depends on how you look at it. There is no need to load the entire module from the loader's point of view. For a function this is different. It may depend on locally defined functions (static that is). >This is on a 4.3 system, but I don't think it is 4.3 specific. > >The reason I ask, is that this is exactly the wrong action for what I >want to do. Namely, a c++ compiler can define data as uninitialized >and also defines an initialiation routine which is resolved at load time >by doing a partial load and then building a table of initialization >routines to be called at program execution. By only using the size, >and not loading the rest of the module the variable is defined in, >the code generated is incorrect. You could say the c++ compiler is wrong in this respect, in that it declares a variable to be uninitialized, and still handles it as 'variable to be automagically initialized', albeit by a runtime function. Of course it is correct in doing so, the question is: is it correct to depend on these expectations regarding the loader (i.e. inclusion of complete modules)? Using initialized variables (having a dummy value) wouldn't solve the problem either; think of some compilers which store initialized strings in ROM segments. Maybe the c++ compiler should force a load of the initializing code by using it in some way; anybody any suggestions? Leo.