Alexander Nasonov wrote
lcaminiti wrote:
Nathan Ridge wrote
GCC 4.5 is in error to allow that. 4.7 does not allow it.
The correct way to use a data member in the lambda is to capture
"this",
and then access the member via "this->member" inside the lambda.
If the above it true ...
Works with the current implementation of ScopeExit that does not use lambdas but it will no longer compile with the implementation of ScopeExit that uses lambdas. Therefore, the lambda implementation of ScopeExit cannot be backward compatible... I will discuss this issue with ScopeExit's main author Alexander Nasonov but this might mean that ScopeExit will never be implemented internally using lambdas, not even on C++11 compilers.
then don't claim backward-compatibility and make sure that lambda implementation can't be implicitly enabled (only if a user defines BOOST_SCOPE_EXIT_USE_LAMBDAS or something like this).
1) I'd propose to never implement BOOST_SCOPE_EXIT using lambdas. There is no advantage for the user in the lambda implementation because I already extended BOOST_SCOPE_EXIT to use variadic macros, capture the object `this_`, and capture no variable (using `void`) all of which without using C++11 and maintaining backward compatibility with the existing BOOST_SCOPE_EXIT syntax. // On all compilers (it never uses C++11 lambdas). BOOST_SCOPE_EXIT(&commit, &persons_) { if(!commit) persons_.pop_back(); } BOOST_SCOPE_EXIT_END 2) However, I'd leave BOOST_SCOPE_EXIT_ALL because it allows for implicit captures using `&` and `=`. This macro uses C++11 lambdas and it is #defined only for C++11 compilers. BOOST_SCOPE_EXIT_ALL and BOOST_SCOPE_EXIT will therefore have different capture semantics (e.g., BOOST_SCOPE_EXIT_ALL cannot capture data members without capturing `this` while BOOST_SCOPE_EXIT can) but if users find that confusing they just don't use SCOPE_EXIT_ALL. // Only on C++11 compilers (same capture semantics of C++11 lambda and therefore different from BOOST_SCOPE_EXIT). BOOST_SCOPE_EXIT_ALL(&, this) { if(!commit) persons_.pop_back(); }; // Use `;` instead of BOOST_SCOPE_EXIT_END 3) Finally, if you #define BOOST_SCOPE_EXIT_CONFIG_NO_CXX11 (or shall this be NO_CPP11? ;) ) then BOOST_SCOPE_EXIT_ALL is never defined not even on C++11 compilers. This way the user is always in control and he/she gets the extra benefits of implicit lambda captures when they apply. What do you think? Thanks. --Lorenzo -- View this message in context: http://boost.2283326.n4.nabble.com/boost-scope-exit-can-MSVC-lambdas-capture... Sent from the Boost - Dev mailing list archive at Nabble.com.