Ensure LogDataWorkerThread::interruptRequested_ atomicity.

[gin-ahirsch]

Includes a couple of refactorings as separate commits.

[nickbnf]

Aren't maxLength_ and indexedSize_ uninitialised?

[z33ky]

Members not listed in the initializer list of a constructor are default-initialized before the body runs and scalars are default-initialized to 0.

[variar]

Scalars are initialized to 0 during zero-initialization that is done for members of value-initialized class types that have no constructors. For IndexingData class there is user-provided constructor that does not have maxLength_ and indexedSize_ the initializer list, so default initialization should be performed and these members should end up to have indeterminate value. I think adding them to class initializer list is safer.

[nickbnf]

@z33ky, do you have a source?

@variar, yes this is my recollection as well, in that case, there is a non-default ctor, so zero-initialisation won't be done.

The simple fact we have to discuss this is a strong argument for explicitly initialising everything anyway :-)

[z33ky]

@nickbnf

Using the C++11 standard draft n3337 (from 2012-01-16)

12.6 Initialization [class.init]

§1

When no initializer is specified for an object of (possibly cv-qualified) class type (or array thereof), or the initializer has the form (), the object is initialized as specified in 8.5.

8.5 Initializers [dcl.init]

--edit--
§ 11

If no initializer is specified for an object, the object is default-initialized; if no initialization is performed, an object with automatic or dynamic storage duration has indeterminate value.

§ 6

To default-initialize an object of type T means:

• if T is a (possibly cv-qualified) class type [...]
• if T is an array type [...]
• otherwise, no initialization is performed.

You seem to be correct, zero-initialization is not performed.

--edit end--

§7

To value-initialize an object of type T means:

• if T is a (possibly cv-qualified) class type [...]
• if T is a (possibly cv-qualified) non-union class type [...]
• if T is an array type [...]
• otherwise, the object is zero-initialized.

§3

To zero-initialize an object or reference of type T means:

• if T is a scalar type (3.9), the object is set to the value 0 (zero), taken as an integral constant expression, converted to T

[nickbnf]

Thanks @z33ky. Sorry but I still don't see how this apply to our case. maxLength_ and indexedSize_, in this patch, don't have any initializer so §10 doesn't apply here. However:

§11

If no initializer is specified for an object, the object is default-initialized; if no initialization is performed, an object with automatic or dynamic storage duration has indeterminate value. [ Note: Objects with static or thread storage duration are zero-initialized, see 3.6.2. — end note ]

So those two variables will be default-initialized (as opposed to value-initiliazed).

Then:
§6

To default-initialize an object of type T means:
— if T is a (possibly cv-qualified) class type (Clause 9), the default constructor for T is called (and the initialization is ill-formed if T has no accessible default constructor);
— if T is an array type, each element is default-initialized;
— otherwise, no initialization is performed.
If a program calls for the default initialization of an object of a const-qualified type T, T shall be a class type with a user-provided default constructor.

Given those two variables are neither classes or array, surely they are not initialised are they?

[z33ky]

Yes, just after posting I realized this and edited the message.

You seem to be correct, zero-initialization is not performed.

[z33ky]

Also I haven't yet mentioned that gin-ahirsch is my account from work. I'll be fixing the PR on Thursday.

[gin-ahirsch]

Rebased with

index bf33169..5312d44 100644
--- a/src/data/logdataworkerthread.h
+++ b/src/data/logdataworkerthread.h
@@ -36,8 +36,6 @@
 class IndexingData
 {
   public:
-    IndexingData() { }
-
     // Get the total indexed size
     qint64 getSize() const;
 
@@ -67,8 +65,8 @@ class IndexingData
     mutable QMutex dataMutex_;
 
     LinePositionArray linePosition_;
-    int maxLength_;
-    qint64 indexedSize_;
+    int maxLength_{0};
+    qint64 indexedSize_{0};
 
     EncodingSpeculator::Encoding encoding_{EncodingSpeculator::Encoding::ASCII7};
 };