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Bug 552

Summary: GCC address sanitizer breaks 16-byte alignment of glibc malloc
Product: Eigen Reporter: Takaki Makino <t-eigen-bugzilla>
Component: Core - generalAssignee: Nobody <eigen.nobody>
Severity: Unknown CC: gael.guennebaud, jacob.benoit.1
Priority: Normal    
Version: 3.2   
Hardware: x86 - 64-bit   
OS: Linux   
Bug Depends on:    
Bug Blocks: 387    

Description Takaki Makino 2013-02-08 16:40:05 UTC
Currently Eigen assumes glibc malloc() returns 16-byte aligned address for all LP64 systems.  Now gcc 4.8 introduces address sanitizer (-fsanitize=address), which is a very powerful tool that effectively detect memory-related bugs.  Unfortunately, when this switch is turned on, the pointer returned by malloc() no longer aligned at 16-byte alignment, and breaks Eigen assumption.
For a quick fix, I propose the following patch:

--- Eigen/src/Core/util/Memory.h        2013-02-09 00:20:40.000000000 +0900
+++ Eigen/src/Core/util/    2013-02-09 00:20:51.000000000 +0900
@@ -27,7 +27,7 @@
 // page 114, "[The] LP64 model [...] is used by all 64-bit UNIX ports" so it's indeed
 // quite safe, at least within the context of glibc, to equate 64-bit with LP64.
 #if defined(__GLIBC__) && ((__GLIBC__>=2 && __GLIBC_MINOR__ >= 8) || __GLIBC__>2) \
- && defined(__LP64__)
+ && defined(__LP64__) && ! defined( __SANITIZE_ADDRESS__ )
Comment 1 Benoit Jacob 2013-02-08 18:20:53 UTC
Good catch! In fact, I think that we should just remove EIGEN_GLIBC_MALLOC_ALREADY_ALIGNED altogether: it doesn't buy us much as we're able to use aligned malloc functions just as well, and it's likely to cause other problems with other kinds of malloc instrumentation.
Comment 2 Gael Guennebaud 2013-02-25 19:19:47 UTC
It still looks better to simply rely on malloc when possible, so:
changeset:   fade198d789b
user:        ggael
date:        2013-02-25 19:17:13
summary:     Fix bug 552: disable EIGEN_GLIBC_MALLOC_ALREADY_ALIGNED when compiling with -fsanitize=address, and allow users to manually tell whether EIGEN_MALLOC_ALREADY_ALIGNED.
Comment 3 Nobody 2019-12-04 12:03:53 UTC
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