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boostorg / move

Boost.org move module
http://boost.org/libs/move
Boost Software License 1.0
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Move Emulation Compile error for gcc < 6 #16

Closed bc-lee closed 5 years ago

bc-lee commented 6 years ago

Consider this code: https://wandbox.org/permlink/jLbuodseGjnw6bIb

boost version: 1.67 CXXFLAGS: -std=c++98

if gcc >= 6 or clang, Move emulation works as expected and run as expected.

However, with gcc < 6 (ex. 5.5), this code fails to compile with these messages:

prog.cc:51:1: error: prototype for 'Handle::Handle(boost::rv<Handle>&)' does not match any in class 'Handle'
 Handle::Handle(BOOST_RV_REF(Handle) other) BOOST_NOEXCEPT {

After I read an answer from stackoverflow ( https://stackoverflow.com/a/44038078/3627572 ), if I redefine BOOST_MAY_ALIAS macro (In my code, #define MAY_ALIAS_MONKEY_PATCH 1), it works as expected, but I don't think it is a good solution for this issue.

jeking3 commented 5 years ago

Could you submit a pull request to the project adding a new test based on your example (as simplified as possible)? This will allow for a code review of the test and then a follow-up fix using the test to prove the fix.

igaztanaga commented 5 years ago

It seems that this is a GCC bug. I've found that MAY_ALIAS is not necessary for GCC compilers older than GCC 4.5 so I applied this patch, which at least helps GCC 4.4-4.8 and GCC 5 users:

https://github.com/boostorg/move/commit/5e2e0f944e6bd7d16fbf49aef03c9c90f937ae52