llvm-c: Types of functions

Hi All,

I’m beginning to learn & explore the LLVM API via the C bindings. Am running into
some troubles but at the moment cannot tell if this is just my misunderstanding/misuse
of the API, or a bug somewhere.

I have a bitcode file generated with ‘clang --emit-llvm’ and I know this is good because
I can run the ‘test’ function inside with lli, no problems.

However I run into issues when I try to get the argument types to the function. The basic
gist of my code is as follows. (Note I snipped the error checking, but everything is returning

My understanding is that I must get a handle (LLVMValueRef) to the function and from that
pull it’s type as a LLVMTypeRef. This would be a ‘function type’, from which I can pull info about
the return type and iterate the arguments, etc. At least, that’s what I’m trying to do in my code:

LLVMContextRef context = LLVMContextCreate();
LLVMMemoryBufferRef fileMemBuff;
“test.bin”, &fileMemBuff, &msg);

LLVMModuleRef module;
context, fileMemBuff, &module, &msg);

LLVMValueRef testFunc = LLVMGetNamedFunction(module, “test”);

if (LLVMIsAFunction(testFunc)) printf(“Is a Function\n”); // ← I do see this message, so far so good
else printf(“Not a Func\n”);

LLVMTypeRef testType;
testType = LLVMTypeOf(testFunc);
printf(“Type is: %d\n”, LLVMGetTypeKind(testType));
printf(“For reference: Function: %d Pointer: %d\n”,
LLVMFunctionTypeKind, LLVMPointerTypeKind);

if( LLVMIsFunctionVarArg(testType)) printf(“is vaarg\n”);
else printf(“no vararg\n”);

And at runtime I see that the LLVMTypeOf is corresponds to LLVMPointerTypeKind.


Is a Function

Type is: 12

For reference: Function: 9 Pointer: 12

Assertion failed: (isa(Val) && “cast() argument of incompatible type!”), function cast, file /Users/davidm/code/contrib/llvm/llvm/include/llvm/Support/Casting.h, line 237.

Shouldn’t this be a function type?

I also can’t seem to find how to learn what type it points to - LLVMPointerType() appears to create a
new pointer-to-X but is there no getter to find what X is for this pointer in hand?

Am on SVN tip on macos.LLVMDumpModule(module) says:

; ModuleID = ‘test.bin’

target datalayout = “e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128”

target triple = “x86_64-apple-macosx10.8.0”

@foo = global i32 0, align 4

; Materializable

; Function Attrs: nounwind ssp uwtable

declare void @test() #0

attributes #0 = { nounwind ssp uwtable “less-precise-fpmad”=“false” “no-frame-pointer-elim”=“true” “no-frame-pointer-elim-non-leaf”=“true” “no-infs-fp-math”=“false” “no-nans-fp-math”=“false” “unsafe-fp-math”=“false” “use-soft-float”=“false” }

And LLVMDumpValue(testFunc):

; Materializable
; Function Attrs: nounwind ssp uwtable
declare void @test() #0

I’ve tried with various signatures for the test function to no effect, at the moment it just happens to be void test(void);.

What am I doing or thinking wrong? It’s possible I’m missing some init calls