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I noticed that AsmPrinter::EmitLinkage doesn't handle ExternalWeakLinkage. Is that an oversight or is something deeper going on? -Dave

On Jul 12, 2010, at 5:27 PM, David Greene wrote: > I noticed that AsmPrinter::EmitLinkage doesn't handle > ExternalWeakLinkage. Is that an oversight or is something > deeper going on? EmitLinkage is never called on external globals. -Chris

What is the difference between WeakAnyLinkage and ExternalWeakLinkage ? They are defined in GlobalValue.h. Thanks Junjie

There is a description of all the possible linkage types at http://llvm.org/docs/LangRef.html#linkage – does this answer your question? (Basically, an extern_weak resp. ExternalWeakLinkage symbol becomes null instead of being an undefined reference) David On 3/16/11 7:06 PM, Junjie Gu wrote: > What is the difference between WeakAnyLinkage and ExternalWeakLinkage > ? They are defined in GlobalValue.h. Thanks > > Junjie > __________________________________________...

So instead of using linkagetypes.weak I should use externalweaklinkage ? Le 11 févr. 2014 18:29, "Reid Kleckner" <rnk at google.com> a écrit : > You'd have to use extern_weak linkage. Clang compiles the foo declaration > to: > $ clang -cc1 -emit-llvm -o - t.c | grep declare.*@foo > declare extern_weak i32 @foo(...) #1 > > >...

...; WeakODRLinkage: Same, but only replaced by something equivalent. > > AppendingLinkage: Special purpose, only applies to global arrays. > > InternalLinkage: Rename collisions when linking (static functions). > > PrivateLinkage: Like Internal, but omit from symbol table. > > ExternalWeakLinkage: ExternalWeak linkage description. > > CommonLinkage: Tentative definitions. > When I have source code like: int x = 0; int main(){...} I end up with an ExternalLinkage flag on x. Why would this not have CommonLinkage? When I have the same code as above and don't initialize x, I en...

...tion exists, the linker will select the first weak definition. Importing a weak definition into a different module can change the order the weak defs are seen by the linker and change the program semantics. Therefore, any WeakAnyLinkage definitions are only imported as declarations, which are given ExternalWeakLinkage. WeakAny aliases are handled similarly (imported as ExternalWeakLinkage aliases). 2.2.2 WeakODRLinkage For WeakODRLinkage, there is a guarantee that all copies will be equivalent, so the issue described above for WeakAny does not exist, and the definition can be imported. For WeakODRLinkage, th...

...ker will select the first > weak definition. Importing a weak definition into a different module can > change the order the weak defs are seen by the linker and change the > program semantics. Therefore, any WeakAnyLinkage definitions are only > imported as declarations, which are given ExternalWeakLinkage. WeakAny > aliases are handled similarly (imported as ExternalWeakLinkage aliases). > > > > 2.2.2 WeakODRLinkage > > > > For WeakODRLinkage, there is a guarantee that all copies will be > equivalent, so the issue described above for WeakAny does not exist, and > t...

...;/div><div>    auto functionInAnotherModule = ModuleB.getFunction(callableName);</div><div>    auto functionType = functionInAnotherModule->getFunctionType();</div><div>    auto localFunction = llvm::Function::Create(functionType, llvm::GlobalValue::LinkageTypes::ExternalWeakLinkage, callableName, &ModuleA);</div><div> </div><div>    Function seems to be copied, together with complex types its using:</div><div>    ; ModuleID = 'JitModule'</div><div>    source_filename = "JitModule"   </div><div>...

...he original module stays the > same, and therefore is not noted in the table below. > > > > Note that there are no InternalLinkage, PrivateLinkage, > AvailableExternallyLinkage, LinkOnce*Linkage, Weak*Linkage, > AppendingLinkage and CommonLinkage declarations. There are no > ExternalWeakLinkage definitions. > > > > > +---------------------------------+------------------------------------------------+ > > | | Importing Module Linkage > | > > | Original Module > +----------------------+--------------------...

Thanks for your clear answer. Do you know what modifier should I use to declare such weak symbols in my llvm intermediate code? So that it can be compiled to the .o file with the weak attribute ? Le 10 févr. 2014 19:44, "Reid Kleckner" <rnk at google.com> a écrit : > COFF doesn't support the same kind of concept of 'weak' that ELF does. > This is the issue that