id summary reporter owner description type status milestone component version severity resolution keywords cc 9578 Adapters (map_keys, map_values) cause undefined behavior (segv, etc) when applied to R-Values, especially in the context of BOOST_FOREACH Igor Lubashev Neil Groves "When applied to r-values (for example, maps returned by value from a function), adapters do not make a copy of the r-value but just capture a reference to it. This makes the returned range_iterator dangerous, if it is used after the r-value (the temporary) is destroyed. In particular, the following use causes undefined behavior on all compilers I'd tested on: g++ (4.1.2, 4.4.3, 4.6.3) and Visual Studio (15 [VC9], 16 [VC10]). {{{ #!cpp BOOST_FOREACH(const string &s, return_map_by_value() | map_keys) ... }}} Note that the following works fine (since BOOST_FOREACH takes care of differentiating between l-values and r-values and does the right thing to r-values): {{{ #!cpp BOOST_FOREACH(const MapType::value_type &v, return_map_by_value()) ... }}} It seems that boost::range::adapters need to do a similar thing to what BOOST_FOREACH is does to identify r-values and make a copy (which the compiler is likely to optimize away). Attached is a test sample and the resulting behavior. The output is from code compiled with g++ 4.6.3 with no optimizations. {{{ $ g++ -I ../include/ container_test.cpp $ ./a.out Test #1 (local variable) Generating map key = '12345' key = 'QWERT' key = 'igor!' Test #2 (value_type) Generating map key = '12345' key = 'QWERT' key = 'igor!' Test #3 (temp ref) Generating map key = '12345' key = 'QWERT' key = 'igor!' Test #4 (range_iterator) Generating map key = '12345' key = 'QWERT' key = 'igor!' Test #5 (bug) Generating map key = '12345APãr`ãr¨ârãr1 ãrÿÿÿÿABCDE1ãrÿÿÿÿQWERTAâr½™ÿÀâr ârHãr¸ãr1àárÿÿÿÿqwertAärH½™ÿPärärHãr¸ãrAårÐãârxârAÀãrÐãr¨ârãrAÀärX™ÿårÐärHãr¸ãrAäârxârA€ärär¨ârãrA€årؽ™ÿÐårårHãr¸ãrA°ârPåârxârA@årPår¨ârãr }}}" Bugs closed To Be Determined range Boost 1.55.0 Problem duplicate ilubashe@…