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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 - general	Assignee:	Nobody <eigen.nobody>
Status:	RESOLVED FIXED
Severity:	Crash	CC:	chtz, gael.guennebaud, jacob.benoit.1
Priority:	Normal
Version:	3.3 (current stable)
Hardware:	All
OS:	All
Whiteboard:
Bug Depends on:
Bug Blocks:	558

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

See:

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: https://forum.kde.org/viewtopic.php?f=74&t=140169

Comment 2 Gael Guennebaud 2018-07-18 21:35:33 UTC

https://bitbucket.org/eigen/eigen/commits/ce3a50205919/
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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