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recently I've stumbled upon this post: Get a function declaration from another llvm::Module

In the comments, @arrowd says something about getGlobalContext(). I am very interested in finding more about this function, because I want to create LLVM types without depending on a context (a context is scoped to a module and I'm working with multiple modules). I've tried to look up this function in the LLVM docs, but I can't find it (https://llvm.org/doxygen/classllvm_1_1LLVMContext.html). Does anyone know if such function still exists? The first post I've linked was made more than 10 years ago so LLVM creators probably have made some changes to the c++ API. if such function doesn't exist anymore, how can I get the global context?

This is an annoying issue because when I'm calling an imported function, the types seem to be correct but the contexts don't match up, which results in very weird errors. for example calling a function that takes an i32 with a 32 bit int results in an error:

Call parameter type does not match function signature!
i32 4
 i32  call void @cool_function(i32 4)
kamkow1
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  • LLVM didn't use to have Context, then it was added with a "global context" as an intermediate state so that any code which didn't have a context handy could use the global one, finally the global context was removed some time around LLVM 4. – Nick Lewycky Aug 29 '22 at 05:23

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Types belong to their context. You cannot have a type without a context, and no context is superior to the others.

This is similar to how different source files in C can contain many different static/private things with the same name, and none of them are superior to the others. (It's similar, it's not exactly the same.)

arnt
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  • Okay, so if types must have a context attached to them, then how can I call a function when it's body lives in a different module and it's parameter types have different contexts? – kamkow1 Aug 28 '22 at 21:13
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    You have to have compatible types in the calling module's context and a compatible extern function in the calling module. – arnt Aug 28 '22 at 21:32