Subject: Re: [boost] Warning policy? local variable hides (i.e. shadows) global variable
From: Vicente J. Botet Escriba (vicente.botet_at_[hidden])
Date: 2015-01-19 02:44:21
Le 15/01/15 14:11, Beman Dawes a écrit :
> GCC and Clang have had a warning for years (-Wshadow): "Warn whenever
> a local variable or type declaration shadows another variable,
> parameter, type, class member (in C++), or instance variable (in
> Objective-C) or whenever a built-in function is shadowed. Note that in
> C++, the compiler warns if a local variable shadows an explicit
> typedef, but not if it shadows a struct/class/enum."
> VC++ 2015 (aka 14.0) Preview has now added a similar warning, C4459.
> For example, "c:\boost\modular\develop\boost\lexical_cast\detail\converter_lexical_streams.hpp(429):
> warning C4459: declaration of 'n' hides global declaration". The VC++
> warning also provides location info so is easy to view both the
> declarations involved. In this case, the declaration "bool
> operator<<(short n)" is shadowing a variable name in the unnamed
> namespace of the calling translation unit.
> The process of clearing these shadow warnings occasionally finds bugs
> that are otherwise difficult to detect. Peter Dimov and I have both
> found bugs in our code in the process of clearing the new C4459
> warning. Even though most of the warnings don't actually signify bugs,
> I'm finding that clearing them makes code clearer and less confusing,
> particularly code I haven't looked at in a long while.
> Should Boost have policy to clear these warnings?
> A lot of the warnings involve function argument names. Should we have
> a guideline to prevent shadow warnings? A convention for argument
> names would make it easier to submit pull requests. Possible
> * Prefix function argument names with "a_". Rationale: The "m_" prefix
> for member names has been a success.
> * Suffix function argument names with "_". Rationale: Short and less
> distracting than "m_" prefix.
Boost is a set of libraries without coding style guidelines. Each author
has its own rules/guidelines. What is desirable is that at least each
source is coherent.
I will suggest that each library add in its documentation if it adheres
to the no-shadow warnings and if it adheres, how the author want the
A global page could be written to this purpose and each library could
reference this page and its approach respect to this guidelines.
Boost list run by bdawes at acm.org, gregod at cs.rpi.edu, cpdaniel at pacbell.net, john at johnmaddock.co.uk