2010 Apr 02 - Fri
Checked Iterators in Microsoft Visual C++
I've wondered why some of my C++ programs seem to run slower than I think they should be
running. Then I came across an article regarding Checked Iterators, and it become clearer
to me where some of my execution speed issues could be. By default, in debug mode,
all standard iterators are bounds checked. This checking can cause a slow down in
execution speed when using standard iterators extensively.
The solution is to set certain macros to selectively enable and disable the checking
on proven code. A
Microsoft MSDN article on Checked Iterators
describes the two symbols used for controlling the checked iterators feature:
- _SECURE_SCL: If defined as 1, unsafe iterator use causes a runtime error. If defined as 0, checked iterators are disabled. The exact behavior of the runtime error depends on the value of _SECURE_SCL_THROWS. The default value for _SECURE_SCL is 1, meaning checked iterators are enabled by default.
- _SECURE_SCL_THROWS: If defined as 1, an out of range iterator use causes an exception at runtime. If defined as 0, the program is terminated by calling invalid_parameter. The default value for _SECURE_SCL_THROWS is 0, meaning the program will be terminated by default. Requires _SECURE_SCL to also be defined.
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