[llvm-dev] Malloc signature errors

[Jameson Nash via llvm-dev]

It looks like you have tried to declare that the size argument integer has
type `int8Type->getPointerTo()`, while the IntPtr type should be the same
as given in the DataLayout `dataLayout.getIntPtrType(Context, 0)`, which
appears to be i64 in your case.


On Fri, Jun 18, 2021 at 6:36 AM zealain via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> I have tried adding attributes like noalias as well, but that didn't help
> either.
>
> Generated by clang (works): %2 = call noalias i8* @malloc(i64 4096) #2
> Generated by my pass (fails): i8*  %malloccall = call noalias i8*
> @malloc(i64 4096)
>
> I had a look at CallInstr::CreateMalloc as well and found out that it
> uses module->getOrInsertFunction(), which seems a bit odd to me. I have
> then also tried to get a pointer to the malloc function itself with
> module->getFunction() and it turns out it couldn't find it. So that would
> raise two additional questions:
>
> 1. Why does CallInstr::CreateMalloc define a new malloc function which
> seems to be broken if it can't find the real one?
> 2. Why does it not find the malloc function in the first place if clang
> can find it?
>
> Regards,
> Z
>
> On Thu, Jun 17, 2021 at 7:49 PM David Blaikie <dblaikie at gmail.com> wrote:
>
>> Might be missing the noalias attribute on the result?
>>
>> On Thu, Jun 17, 2021 at 10:46 AM zealain via llvm-dev <
>> llvm-dev at lists.llvm.org> wrote:
>>
>>> Hello
>>>
>>> I am trying to insert malloc calls in my function pass, yet it keeps
>>> complaining about the parameter type:
>>>
>>> Call parameter type does not match function signature!
>>> i64 4096
>>>  i8*  %malloccall = tail call i8* @malloc(i64 4096)
>>>
>>> Comparing this to a call generated by simply having a malloc in the C
>>> code, I cannot spot significant differences. The following (generated by
>>> clang) works just fine:
>>>
>>> %2 = call noalias i8* @malloc(i64 4096) #2
>>>
>>> Why does one work but the other doesn't? Below is the code I use to
>>> generate the instruction:
>>>
>>> Type *int8Type = Type::getInt8Ty(this->currentFunction->getContext());
>>> Type *int64Type = Type::getInt64Ty(this->currentFunction->getContext());
>>>
>>> auto allocSize = ConstantInt::get(int64Type, 4096);
>>>
>>> Instruction* mallocInstr =
>>> CallInst::CreateMalloc(this->currentFunction->getEntryBlock().getFirstNonPHI(),
>>>
>>> int8Type->getPointerTo(), int8Type, allocSize,
>>>                                                   nullptr, nullptr, "");
>>>
>>> I tried changing up the types already but didn't find a combination that
>>> works yet. Any hints would be appreciated.
>>>
>>> Regards,
>>> Z
>>> _______________________________________________
>>> LLVM Developers mailing list
>>> llvm-dev at lists.llvm.org
>>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>
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