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Bug 1432

Summary: Bypass memcpy for unsuitable scalar types (aka make a better use of C++11 type-traits)
Product: Eigen Reporter: Gael Guennebaud <gael.guennebaud>
Component: Core - generalAssignee: Nobody <eigen.nobody>
Severity: Crash CC: chtz, gael.guennebaud, jacob.benoit.1
Priority: Normal    
Version: 3.3 (current stable)   
Hardware: All   
OS: All   
Bug Depends on:    
Bug Blocks: 558    

Description Gael Guennebaud 2017-06-06 08:49:33 UTC

basically some types like std::string might not be copiable by memcpy if too short. The proposed fix is to use c++11 type-traits to detect this and bypass memcpy (in Memory.h) in such cases. In c++98, we would document it a known pitfall.

In the same vein, NumTraits::RequireInitialization currently default to:

RequireInitialization = internal::is_arithmetic<T>::value ? 0 : 1

whereas c++11 provides more accurate type-traits for that.
Comment 1 Gael Guennebaud 2017-06-06 08:50:24 UTC
oops, the missing link is:
Comment 2 Gael Guennebaud 2018-07-18 21:35:33 UTC
Summary:     Bug 1432: fix conservativeResize for non-relocatable scalar types. For those we need to by-pass realloc routines and fall-back to allocate as new - copy - delete. The remaining problem is that we don't have any mechanism to accurately determine whether a type is relocatable or not, so currently let's be super conservative using either RequireInitialization or std::is_trivially_copyable
Comment 3 Nobody 2019-12-04 17:01:17 UTC
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