[PATCH] D153376: Introducing llvm-cm: A Cost Model Tool

[Ondrej Sykora via Phabricator via llvm-commits]

ondrasej added inline comments.


================
Comment at: llvm/tools/llvm-cm/llvm-cm.cpp:70
+// Class for error handling.  
+class ExitIf {
+   public:
----------------
mtrofin wrote:
> nit: `class ExitIf final`
> 
> upon looking more closely at the usage pattern - @ondrasej , why raii and not just a function call? raii will exit at scope exit, which is undesirable (the goal is to exit right away). A function call "just works" because `exit(1)`, no?
As discussed offline yesterday: RAII is there to make the streaming operators after `ExitIf()` work.

With RAII, and with the intended use (`ExitIf(Cond) << "Some message";`), the following happens:
1. a temporary `ExitIf` instance is created and takes note of `Cond`,
2. all streaming operators are applied to the temporary (collecting the messages),
3. it's a temporary value (there's no variable name), so its scope is limited to the statement where it appears.

Basically, it processes the chain of `<<`, and then immediately exits.


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https://reviews.llvm.org/D153376