[LLVMdev] llvm line number of an instruction

[Eric Christopher]

The line numbers there aren't the line numbers of the instructions in the
.ll file, they're metadata attached to llvm instructions describing the
original source program (e.g. C++). So you'd need to have a front end
attaching line information to instructions and other debug information in
the module (very little if all you want is line numbers) to get the line
numbers.

-eric


On Mon, Feb 18, 2013 at 11:04 AM, Alexandru Ionut Diaconescu <
cyrusthevirus001x at yahoo.com> wrote:

> Hello everybody,
>
> I want to get the line number of an instruction (and also of a variable
> declaration - alloca and global). The instruction is saved in an array of
> instructions. I have the function:
>
>     Constant* metadata::getLineNumber(Instruction* I){
>         if (MDNode *N = I->getMetadata("dbg")) { // this if is never
> executed
>             DILocation Loc(N);
>             unsigned Line = Loc.getLineNumber();
>             return ConstantInt::get(Type::getInt32Ty(I->getContext()),
> Line);
>         }   // else {
>           //  return NULL; }
>     }
>
> and in my main() I have :
>
>     errs()<<"\nLine number is "<<*metadata::getLineNumber(allocas[p]);
>
> the result is NULL since `I->getMetadata("dbg")` is false.
>
> Is there a possibility to enable dbg flags in LLVM without rebuilding the
> LLVM framework, like using a flag when compiling the target program or when
> running my pass (I used -debug) ?
>
> Compiling a program with “-O3 -g” should give full debug information, but
> I still have the same result. I am aware of
> http://llvm.org/docs/SourceLevelDebugging.html , from where I can see
> that is quite easy to take the source line number from a metadata field.
>
> PS: for Allocas, it seems that I have to use findDbgDeclare method from
> DbgInfoPrinter.cpp.
>
> Thank you in advance !
>
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