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Where No Init Has Gone Before

Can your code have logging entries whose sensitive messages don't show up in the shipped binaries? And can the following code snippet ever work?

static bool initially_false = false;
void no_one_calls_me() { DO_ON_INIT(initially_false = true); }
int main() {assert(initially_false == true); return 0;}

Well yes, this is actual working C++17 code! And yes, we can use this tool to produce a logger with vanishing strings!

As part of this talk we will go behind the scenes of the DO_ON_INIT utility, the process involved in developing the idea and its surprisingly simple implementation details (under 20 lines of C++17 code, and even less in C++20).

We shall also see how this utility is instrumental in making possible the no-strings-attached logger and its associated automatically-generated decoding facility. We will implement a simple obfuscation technique which replaces logged strings with hashes at compile-time, to avoid shipping binaries containing sensitive textual giveaways. To decode such logs (in a separate decoder utility) we shall use DO_ON_INIT to automatically collect and register all the logged strings system-wide, along with their hashes, without requiring any additional tool (such as an in-house pre-processor).

This is yet another example of emergent behavior in C++, consisting of unrelated language features being put to use together in a novel and unexpected way. Could your idea be next?