[llvm-dev] Printing while developing on LLVM/Clang code

[Matt P. Dziubinski via llvm-dev]

On 2/11/2021 13:20, Deep Majumder via llvm-dev wrote:
> Hi everyone,
> I have found that `print <expr>` often doesn't work while running a 
> debug build of clang in lldb. So I have to resort to print statements. 
> Since <iostream> is not used inside LLVM/Clang code, I have to include 
> it in manually and remember to remove it before committing. Is there a 
> better way to do this, either in lldb or insert print statements?

Depending on the type of <expr> it's also worth trying `print 
<expr>.dump()` or `print <expr>.print()`.

See: https://bholt.org/posts/llvm-debugging.html, 
https://llvm.org/docs/WritingAnLLVMPass.html#the-print-method, 
https://clang.llvm.org/hacking.html#debugging

Otherwise this may come in handy:
LLVM_DEBUG(dbgs() << "I am here!\n");

See: 
https://llvm.org/docs/ProgrammersManual.html#the-llvm-debug-macro-and-debug-option

Don't forget to enable it: "One additional nice thing about the 
LLVM_DEBUG() macro is that you can enable or disable it directly in gdb. 
Just use “set DebugFlag=0” or “set DebugFlag=1” from the gdb if the 
program is running. If the program hasn’t been started yet, you can 
always just run it with -debug."

Best,
Matt