[LOGCXX-183] Compiler warning: dereferencing type-punned pointer will break strict-aliasing rules

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.10.0
• Component/s: Build
• Assignee: Curt Arnold
• Reporter: Myles Bunbury
• Created: 12/Jun/07 15:26
• Updated: 25/Oct/07 22:43
• Resolved: 25/Oct/07 22:43

Description

The following line of code:
void* oldPtr = ObjectPtrBase::exchange((volatile void**) &this->p, newPtr);
in the ObjectPtrT template class (objectptr.h) produces a 'dereferencing type-punned pointer will break strict aliasing rules' compiler warning.

This line can be found (with slight variances) in the destructor, operator=(const int& null), operator=(T* p1), and operator=(const ObjectPtrT& p1) functions.

This warning was produced with gcc v4.1.1 using the following compiler options:
-Wall -Wextra -Wno-unused-parameter -O3 -mtune-i686

After investigating, the warning is being caused by the first parameter.

Replacing all instances of the aforementioned code with the following makes the warning disappear:
T** pp = &this->p;
void* oldPtr = ObjectPtrBase::exchange((volatile void**) pp, newPtr);

A temporary workaround is to use the '-fno-strict-aliasing' compiler option.