Re: [boost] Compiler warnings after boost update

Subject: Re: [boost] Compiler warnings after boost update
From: Agustín K-ballo Bergé (kaballo86_at_[hidden])
Date: 2015-09-25 08:51:35

On 9/25/2015 3:43 AM, Auer, Jens wrote:
> What I really don't like is that Boost makes it impossible for my code to compile the
> warning settings I want. What would you think of a STL delivered with your compiler
> that generates warnings?

It's likely that standard library implementations would generate 
warnings if not masked with `-isystem` or similar. For instance, libc++ 
only very recently started to care about warnings, nobody ever sees them 
due to `#pragma system_header`.

Lots of warnings are of the form "you did this perfectly fine thing X, 
but are you sure you did not mean Y instead?". There tends to be a lot 
of these in implementations like Boost, the STL, and the standard 
library. "Did you forget to use this alias?" No, it's triggering a 
template instantiation that will cause a substitution failure if the 
arguments violate a precondition.

I remember a particular piece of code that exploited properties of the 
comma operator, it was a single line that handled all possible input 
cases. Obviously the compiler suspected, "your code appears to be doing 
exactly what you meant it to do by abusing the comma operator, it's 
probably wrong", and it suspected so strongly that there was no way to 
shut down the warning at all while keeping use of the comma operator. 
This particular popular compiler forced this single line of code to be 
split into 8 different template specializations, true errors were 
introduced in this pointless duplication process.

Not every warning is valuable, some are just noise, some only attempt to 
restrict use of the language to a particular subset, others are just 
simply bogus. Sometimes suppressing them is not worth the cost, 
sometimes they can't even be suppressed.

Some warnings might be worth enforcing, turning them into errors while 
compiling/running tests. Blindly littering the code with `#pragma`s to 
silence noise doesn't really help, specially when you already have 
`-isystem`.

Regards,
-- 
Agustín K-ballo Bergé.-
http://talesofcpp.fusionfenix.com