[LLVMdev] DEBUG macro for log message postponing

[Jonathan Roelofs]

On 6/23/15 8:28 AM, Frank Winter wrote:
> A pass first collects some log data in form of strings and at some later
> point decides depending on program state whether to print it to dbgs()
> or not. In other words the debug stream would be totally flooded if
> every string was printed. I was thinking of guarding a std::stringstream
> object with the DEBUG macro. Something like
>
> DEBUG(std::stringstream ss);
> DEBUG(ss << "Conditional logging data" << I << "\n");
>
> ... at some later stage ...
>
> DEBUG( if (log_me) dbgs() << ss.str());
>
> However, LLVM doesn't like the above construct. In LLVM, how can one
> postpone some debugging logs for later printing?

What you're asking for is usually written as:

   #ifndef NDEBUG
   std::stringstream ss
   #endif
   DEBUG(ss << "Conditional logging data" << I << "\n");
   DEBUG( if (log_me) dbgs() << ss.str());


Jon

>
> Many thanks,
> Frank
>
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-- 
Jon Roelofs
jonathan at codesourcery.com
CodeSourcery / Mentor Embedded