llvm dev - Apr 2013 - [LLVMdev] How to cast Value* to ConstantDataArray*

I extended the LLVM Kaleidoscope example to support Strings. I added a
StringExprAST, which has the virtual Codegen method impl as follows:

Value *StringExprAST::Codegen() {
  StringRef r(Val);
  return ConstantDataArray::getString(getGlobalContext(), r, false);
}

I am trying to concatenate Strings and have a ConcatExprAST with its
Codegen method. Upon trying to access the data in the ConstantDataArray, I
need to cast the Value* back to a ConstantDataArray* in order to use the
getAsString() method.

I tried:

ConstantDataArray * cda = cast<ConstantDataArray>(v);

where v is a Value*.  It does not work.

How can I do this?

Thanks for any help.
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On Sat, Apr 20, 2013 at 5:15 PM, Richard Catlin
<richard.m.catlin at gmail.com>wrote:
> I extended the LLVM Kaleidoscope example to support Strings. I added a
> StringExprAST, which has the virtual Codegen method impl as follows:
>
> Value *StringExprAST::Codegen() {
>   StringRef r(Val);
>   return ConstantDataArray::getString(getGlobalContext(), r, false);
> }
>
> I am trying to concatenate Strings and have a ConcatExprAST with its
> Codegen method. Upon trying to access the data in the ConstantDataArray, I
> need to cast the Value* back to a ConstantDataArray* in order to use the
> getAsString() method.
>
> I tried:
>
> ConstantDataArray * cda = cast<ConstantDataArray>(v);
>
> where v is a Value*.  It does not work.
>
*How* does it not work? You need to give us more information. Also make
sure that you have read <
http://llvm.org/docs/ProgrammersManual.html#the-isa-cast-and-dyn-cast-templates
>.
-- Sean Silva
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ConstantDataArray * cda = cast<ConstantDataArray>(v);
throws this error: Assertion failed: (isa<X>(Val) &&
"cast<Ty>() argument
of incompatible type!"), function cast, file
/Users/rcatlin1/lldb/llvm/include/llvm/Support/Casting.h, line 208

Thanks for the help.
Richard Catlin



On Sat, Apr 20, 2013 at 3:37 PM, Sean Silva <silvas at purdue.edu> wrote:
>
>
>
> On Sat, Apr 20, 2013 at 5:15 PM, Richard Catlin <
> richard.m.catlin at gmail.com> wrote:
>
>> I extended the LLVM Kaleidoscope example to support Strings. I added a
>> StringExprAST, which has the virtual Codegen method impl as follows:
>>
>> Value *StringExprAST::Codegen() {
>>   StringRef r(Val);
>>   return ConstantDataArray::getString(getGlobalContext(), r, false);
>> }
>>
>> I am trying to concatenate Strings and have a ConcatExprAST with its
>> Codegen method. Upon trying to access the data in the
ConstantDataArray, I
>> need to cast the Value* back to a ConstantDataArray* in order to use
the
>> getAsString() method.
>>
>> I tried:
>>
>> ConstantDataArray * cda = cast<ConstantDataArray>(v);
>>
>> where v is a Value*.  It does not work.
>>
> *How* does it not work? You need to give us more information. Also make
> sure that you have read <
>
http://llvm.org/docs/ProgrammersManual.html#the-isa-cast-and-dyn-cast-templates
> >.
>
> -- Sean Silva
>
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