llvm dev - Dec 2013 - [LLVMdev] Newbie question: LLVM IR, printf, and varargs

I just tried adding the cast but it didn't help.  I have the feeling that I
am overlooking something very obvious, but I can't seem to figure out what
it is.  Thanks for your suggestion, though.


-- Mikael



2013/12/3 Eli Bendersky <eliben at google.com>
>
>
>
> On Tue, Dec 3, 2013 at 2:29 PM, Mikael Lyngvig <mikael at
lyngvig.org> wrote:
>
>> Hi,
>>
>> I am trying to print two strings using printf.  I have tried various
>> things, but keep getting this error:
>>
>>     llc: printf.ll:4:11: error: '@printf' defined with type
'i32 (i8*,
>> ...)*'
>>         %1 = call i32 @printf(i8* null, i8*, i8* null)
>>
>> The code is:
>>
>>    declare i32 @printf(i8* nocapture readonly, ...) nounwind
>>
>>    define i32 @main() nounwind {
>>       %1 = call i32 @printf(i8* null, i8* null)
>>       ret i32 0
>>   }
>>
>> I am aware that the call will core dump, but I am initially only trying
>> to figure out why LLC won't accept the call itself.  I started out
trying
>> with real values and then reduced it to the above to see if I could
make it
>> work.  Comparing with the output of Clang didn't help; it does the
same -
>> passes in two i8* pointers and declares @printf in the same way (and
LLC
>> accepts the Clang output as valid input).  The Clang code goes as
follows
>> (edited snippet):
>>
>> @.str = private unnamed_addr constant [11 x i8] c"Error:
%s\0A\00", align
>> 1
>> @.str1 = private unnamed_addr constant [5 x i8] c"Test\00",
align 1
>>
>> define i32 @main() nounwind {
>>   %1 = tail call i32 (i8*, ...)* @printf(i8* getelementptr inbounds
([11
>> x i8]* @.str, i32 0, i32 0), i8* getelementptr inbounds ([5 x i8]*
@.str1,
>> i32 0, i32 0)) nounwind
>>   ret i32 0
>> }
>>
>> declare i32 @printf(i8* nocapture readonly, ...) nounwind
>>
>> A good thing about this question is that the answer will find its way
>> into the Mapping Highlevel doc, which is why I am asking it in the
first
>> place.
>>
>> This is on Windows using a 32-bit version of LLVM llc v3.4 (built about
a
>> week ago).
>>
>> I searched the LR, the FAQ, and Google but found nothing of relevance.
>>
>>
> You're missing the cast, IMHO. The cast appeases the LLVM type checker
> w.r.t. mismatching function type
>
> Eli
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20131203/39ec34b2/attachment.html>

This code:

declare i32 @printf(i8* nocapture readonly, ...) nounwind

define i32 @bar(i8* %c, i32 %i) #0 {
entry:
  %call = tail call i32 (i8*, ...)* @printf(i8* %c, i8* %c)
  ret i32 %call
}

Is accepted without complaints by close-to-trunk llc on my Ubuntu machine.

Eli


On Tue, Dec 3, 2013 at 2:58 PM, Mikael Lyngvig <mikael at lyngvig.org>
wrote:
> I just tried adding the cast but it didn't help.  I have the feeling
that
> I am overlooking something very obvious, but I can't seem to figure out
> what it is.  Thanks for your suggestion, though.
>
>
> -- Mikael
>
>
>
> 2013/12/3 Eli Bendersky <eliben at google.com>
>
>>
>>
>>
>> On Tue, Dec 3, 2013 at 2:29 PM, Mikael Lyngvig <mikael at
lyngvig.org>wrote:
>>
>>> Hi,
>>>
>>> I am trying to print two strings using printf.  I have tried
various
>>> things, but keep getting this error:
>>>
>>>     llc: printf.ll:4:11: error: '@printf' defined with type
'i32 (i8*,
>>> ...)*'
>>>         %1 = call i32 @printf(i8* null, i8*, i8* null)
>>>
>>> The code is:
>>>
>>>    declare i32 @printf(i8* nocapture readonly, ...) nounwind
>>>
>>>    define i32 @main() nounwind {
>>>       %1 = call i32 @printf(i8* null, i8* null)
>>>       ret i32 0
>>>   }
>>>
>>> I am aware that the call will core dump, but I am initially only
trying
>>> to figure out why LLC won't accept the call itself.  I started
out trying
>>> with real values and then reduced it to the above to see if I could
make it
>>> work.  Comparing with the output of Clang didn't help; it does
the same -
>>> passes in two i8* pointers and declares @printf in the same way
(and LLC
>>> accepts the Clang output as valid input).  The Clang code goes as
follows
>>> (edited snippet):
>>>
>>> @.str = private unnamed_addr constant [11 x i8] c"Error:
%s\0A\00",
>>> align 1
>>> @.str1 = private unnamed_addr constant [5 x i8]
c"Test\00", align 1
>>>
>>> define i32 @main() nounwind {
>>>   %1 = tail call i32 (i8*, ...)* @printf(i8* getelementptr inbounds
([11
>>> x i8]* @.str, i32 0, i32 0), i8* getelementptr inbounds ([5 x i8]*
@.str1,
>>> i32 0, i32 0)) nounwind
>>>   ret i32 0
>>> }
>>>
>>> declare i32 @printf(i8* nocapture readonly, ...) nounwind
>>>
>>> A good thing about this question is that the answer will find its
way
>>> into the Mapping Highlevel doc, which is why I am asking it in the
first
>>> place.
>>>
>>> This is on Windows using a 32-bit version of LLVM llc v3.4 (built
about
>>> a week ago).
>>>
>>> I searched the LR, the FAQ, and Google but found nothing of
relevance.
>>>
>>>
>> You're missing the cast, IMHO. The cast appeases the LLVM type
checker
>> w.r.t. mismatching function type
>>
>> Eli
>>
>>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20131203/3afaad55/attachment.html>

Whoops...  Seems I forgot the asterisk (*) after the cast.  Or something.
 Because I did insert the cast and it didn't work.  But NOW it works.
 Thank you for spending some time on this - and also for presenting the
solution.


-- Mikael


2013/12/4 Eli Bendersky <eliben at google.com>
> This code:
>
> declare i32 @printf(i8* nocapture readonly, ...) nounwind
>
> define i32 @bar(i8* %c, i32 %i) #0 {
> entry:
>   %call = tail call i32 (i8*, ...)* @printf(i8* %c, i8* %c)
>   ret i32 %call
> }
>
> Is accepted without complaints by close-to-trunk llc on my Ubuntu machine.
>
> Eli
>
>
> On Tue, Dec 3, 2013 at 2:58 PM, Mikael Lyngvig <mikael at
lyngvig.org> wrote:
>
>> I just tried adding the cast but it didn't help.  I have the
feeling that
>> I am overlooking something very obvious, but I can't seem to figure
out
>> what it is.  Thanks for your suggestion, though.
>>
>>
>> -- Mikael
>>
>>
>>
>> 2013/12/3 Eli Bendersky <eliben at google.com>
>>
>>>
>>>
>>>
>>> On Tue, Dec 3, 2013 at 2:29 PM, Mikael Lyngvig <mikael at
lyngvig.org>wrote:
>>>
>>>> Hi,
>>>>
>>>> I am trying to print two strings using printf.  I have tried
various
>>>> things, but keep getting this error:
>>>>
>>>>     llc: printf.ll:4:11: error: '@printf' defined with
type 'i32 (i8*,
>>>> ...)*'
>>>>         %1 = call i32 @printf(i8* null, i8*, i8* null)
>>>>
>>>> The code is:
>>>>
>>>>    declare i32 @printf(i8* nocapture readonly, ...) nounwind
>>>>
>>>>    define i32 @main() nounwind {
>>>>       %1 = call i32 @printf(i8* null, i8* null)
>>>>       ret i32 0
>>>>   }
>>>>
>>>> I am aware that the call will core dump, but I am initially
only trying
>>>> to figure out why LLC won't accept the call itself.  I
started out trying
>>>> with real values and then reduced it to the above to see if I
could make it
>>>> work.  Comparing with the output of Clang didn't help; it
does the same -
>>>> passes in two i8* pointers and declares @printf in the same way
(and LLC
>>>> accepts the Clang output as valid input).  The Clang code goes
as follows
>>>> (edited snippet):
>>>>
>>>> @.str = private unnamed_addr constant [11 x i8] c"Error:
%s\0A\00",
>>>> align 1
>>>> @.str1 = private unnamed_addr constant [5 x i8]
c"Test\00", align 1
>>>>
>>>> define i32 @main() nounwind {
>>>>   %1 = tail call i32 (i8*, ...)* @printf(i8* getelementptr
inbounds
>>>> ([11 x i8]* @.str, i32 0, i32 0), i8* getelementptr inbounds
([5 x i8]*
>>>> @.str1, i32 0, i32 0)) nounwind
>>>>   ret i32 0
>>>> }
>>>>
>>>> declare i32 @printf(i8* nocapture readonly, ...) nounwind
>>>>
>>>> A good thing about this question is that the answer will find
its way
>>>> into the Mapping Highlevel doc, which is why I am asking it in
the first
>>>> place.
>>>>
>>>> This is on Windows using a 32-bit version of LLVM llc v3.4
(built about
>>>> a week ago).
>>>>
>>>> I searched the LR, the FAQ, and Google but found nothing of
relevance.
>>>>
>>>>
>>> You're missing the cast, IMHO. The cast appeases the LLVM type
checker
>>> w.r.t. mismatching function type
>>>
>>> Eli
>>>
>>>
>>
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20131204/f94e03db/attachment.html>